diff --git a/README.md b/README.md
index 3e6bab47..038d142f 100644
--- a/README.md
+++ b/README.md
@@ -7,16 +7,32 @@
### Overview
The project contains the VHDL code for a **complete DEC PDP-11 system**:
-a PDP-11/70 CPU with memory management unit, but without floating point unit,
+a
+[PDP-11/70](http://www.bitsavers.org/pdf/dec/pdp11/1170/EK-KB11C-TM-001_1170procMan.pdf)
+CPU with memory management unit, but without floating point unit,
a complete set of mass storage peripherals
-(RK11/RK05, RL11/RL02, RK70/RP06, TM11/TU10)
+([RK11/RK05](http://www.bitsavers.org/pdf/dec/unibus/RK11-C_manual1971.pdf),
+[RL11/RL02](http://www.bitsavers.org/pdf/dec/disc/rl01_rl02/EK-RL122-TM-001_techAug82.pdf),
+[RH70](http://www.bitsavers.org/pdf/dec/unibus/CSS-MO-F-5.2-27_RH70_Option_Description_Feb77.pdf)/[RP06](http://www.bitsavers.org/pdf/dec/disc/rp04_rp05_rp06/EK-RP056-MM-01_maint_Dec75.pdf),
+[TM11/TU10](http://www.bitsavers.org/pdf/dec/magtape/tm11/TM11_Manual.pdf))
and a rather complete set of UNIBUS peripherals
-(DL11, LP11, PC11, and DEUNA),
+([DL11](http://www.bitsavers.org/pdf/dec/unibus/EK-DL11-TM-003_DL11_Asynchronous_Line_Interface_Manual_Sep75.pdf),
+[LP11](http://www.bitsavers.org/pdf/dec/unibus/LP11_UsersMan.pdf),
+[PC11](http://www.bitsavers.org/pdf/dec/unibus/PC11_Reader-Punch_Manual.pdf),
+[DZ11](http://www.bitsavers.org/pdf/dec/unibus/EK-DZ110-TM-002_DZ11_Asynchronous_Multiplexer_Technical_Manual_Oct78.pdf), and
+[DEUNA](http://www.bitsavers.org/pdf/dec/unibus/EK-DEUNA-TM-PRE_TechMan_Dec82.pdf)),
and last but not least a cache and memory controllers for SRAM, PSRAM and
SDRAM (via Xilinx MIG core).
-The design is **FPGA proven**, runs currently on
-Digilent Arty, Basys3, CmodA7, Nexys4, Nexys3, Nexys2 and S3board boards
-and boots 5th Edition UNIX and 2.11BSD UNIX.
+The design is **FPGA proven**, runs currently on Digilent
+[Arty A7](rtl/sys_gen/w11a/arty),
+[Basys3](rtl/sys_gen/w11a/basys3),
+[Cmod A7](rtl/sys_gen/w11a/cmoda7),
+[Nexys A7](rtl/sys_gen/w11a/nexys4d),
+[Nexys4](rtl/sys_gen/w11a/nexys4),
+[Nexys3](rtl/sys_gen/w11a/nexys3),
+[Nexys2](rtl/sys_gen/w11a/nexys2) and
+[S3board](rtl/sys_gen/w11a/s3board)
+boards and boots 5th Edition UNIX and 2.11BSD UNIX.
For more information look into:
- w11 project [home page](https://wfjm.github.io/home/w11/)
diff --git a/doc/README_known_issues.md b/doc/README_known_issues.md
index 875c59dd..00396b9f 100644
--- a/doc/README_known_issues.md
+++ b/doc/README_known_issues.md
@@ -230,9 +230,37 @@ to avoid potential damage.
Looking forward to receive test reports.
#### Fix
-Purchased Nexys A7-100 board after the
-[Nexys4 board broke](https://wfjm.github.io/blogs/w11/2019-07-27-nexys4-obituary.html),
-tested, and fixed one silly mistake. Closed with commit
+The Nexys4 _(classic, with 16 MByte PSRAM)_ board, on which most of the recent
+w11 was done, broke in late July 2019
+(see [blog](https://wfjm.github.io/blogs/w11/2019-07-27-nexys4-obituary.html))
+and a Nexys A7 was ordered as replacement.
+
+Basic tests with the test designs
+[sys_tst_serloop2](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/tst_serloop/nexys4d/sys_tst_serloop2_n4d.vhd) and
+[sys_tst_rlink_n4d](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/tst_rlink/nexys4d/sys_tst_rlink_n4d.vhd)
+and the BRAM-only w11 design
+[sys_w11a_br_n4d](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/w11a/nexys4d_bram/sys_w11a_br_n4d.vhd) worked fine.
+
+But all tests involving the DDR2 memory interface failed. The culprit was
+quickly found, it was a mistake in the MIG configuration
+[mig_a.prj](https://github.com/wfjm/w11/blob/master/rtl/bplib/nexys4d/mig_a.prj),
+the polarity of the `SYS_RST` signal was `ACTIVE LOW` instead of `ACTIVE HIGH`.
+After fixing this, the test designs
+[sys_tst_mig_n4d](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/tst_mig/nexys4d/sys_tst_mig_n4d.vhd) and
+[sys_tst_sram_n4d](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/tst_sram/nexys4d/sys_tst_sram_n4d.vhd)
+as well as the w11 implementation
+[sys_w11a_n4d](https://github.com/wfjm/w11/blob/master/rtl/sys_gen/w11a/nexys4d/sys_w11a_n4d.vhd) worked right away.
+
+The [tst_sram](https://github.com/wfjm/w11/tree/master/rtl/sys_gen/tst_sram)
+designs show nicely that the DDR2 on the Nexys A7 board is slightly slower
+than the DDR3 on the Arty A7 board
+```
+ Board test time clock period UI_CLK
+ Nexys A7 37.36 s 3333 ps 75.0 MHz
+ Arty A7 35.77 s 3000 ps 83.3 MHz
+```
+
+Closed with commit
[563e230](https://github.com/wfjm/w11/commit/563e230).
### V0.66-1 {[issue #8](https://github.com/wfjm/w11/issues/8)} -- TM11 controller doesn't support odd transfer size
diff --git a/doc/w11a_os_guide.md b/doc/w11a_os_guide.md
index 57736663..bc223891 100644
--- a/doc/w11a_os_guide.md
+++ b/doc/w11a_os_guide.md
@@ -12,9 +12,9 @@
### I/O emulation setup
-All UNIBUS peripherals which exchange data (currently DL11, LP11, PC11, RK11,
-RL11, RPRH, TM11, and DENUA ) are currently emulated via a backend process. The
-communication between FPGA board and backend server can be via
+All UNIBUS peripherals which exchange data (currently DL11, DZ11, LP11, PC11,
+DEUNA, RK11, RL11, RPRH, and TM11) are currently emulated via a backend
+process. The communication between FPGA board and backend server can be via
- Serial port
- via an integrated USB-UART bridge
@@ -26,7 +26,8 @@ communication between FPGA board and backend server can be via
2017 one gets kernels with 16 ms default latency again, thanks to
[kernel patch 9589541](https://patchwork.kernel.org/patch/9589541/).
**For newer systems it is essential to install a udev rule** which
- automatically sets low latency, see [docu](../tools/sys/README.md).
+ automatically sets low latency, see
+ [documentation in tools/sys](../tools/sys/README.md).
- via RS232 port, as on S3board and Nexys2
- using a serial port (/dev/ttySx) is limited to 115 kBaud on most PCs.
- using a USB-RS232 adapter was tested up to 460k Baud.
@@ -52,45 +53,50 @@ Recommended setup for best performance (boards ordered by vintage):
| Board | Channel/Interface | nom. speed | peak transfer rate |
| :--------- | :--------------------- | :----------- | -----------------: |
-| Arty A7 | USB-UART bridge | 12M Baud | 1090 kB/sec |
-| Basys3 | USB-UART bridge | 12M Baud | 1090 kB/sec |
-| Cmod A7 | USB-UART bridge | 12M Baud | 1090 kB/sec |
-| Nexys A7 | USB-UART bridge | 12M Baud | 1090 kb/sec |
-| Nexys4 | USB-UART bridge | 12M Baud | 1090 kb/sec |
-| Nexys3 | Cypress FX2 USB | USB2.0 speed | 30000 kB/sec |
-| Nexys2 | Cypress FX2 USB | USB2.0 speed | 30000 kB/sec |
-| S3board | RS232+USB-RS232 cable | 460k Baud | 41 kB/sec |
+| [Arty S7](https://wfjm.github.io/home/w11/inst/boards.html#digi_artys7) | USB-UART bridge | 12M Baud | 1090 kB/sec |
+| [Arty A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_arty) | USB-UART bridge | 12M Baud | 1090 kB/sec |
+| [Basys3](https://wfjm.github.io/home/w11/inst/boards.html#digi_basys3) | USB-UART bridge | 12M Baud | 1090 kB/sec |
+| [Cmod A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_cmoda7) | USB-UART bridge | 12M Baud | 1090 kB/sec |
+| [Nexys A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexysa7) | USB-UART bridge | 12M Baud | 1090 kb/sec |
+| [Nexys4](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4) | USB-UART bridge | 12M Baud | 1090 kb/sec |
+| [Nexys3](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys3) | Cypress FX2 USB | USB2.0 speed | 30000 kB/sec |
+| [Nexys2](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys2) | Cypress FX2 USB | USB2.0 speed | 30000 kB/sec |
+| [S3board](https://wfjm.github.io/home/w11/inst/boards.html#digi_s3board) | RS232+USB-RS232 cable | 460k Baud | 41 kB/sec |
### FPGA Board setup
Recommended setups
-- Arty
+- [Arty A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_arty) or
+ [Arty S7](https://wfjm.github.io/home/w11/inst/boards.html#digi_artys7)
- connect USB cable to micro-USB connector labeled 'J10'
- to configure via vivado hardware server `make .vconfig`
-- Basys3
+- [Basys3](https://wfjm.github.io/home/w11/inst/boards.html#digi_basys3)
- connect USB cable to micro-USB connector labeled 'PROG'
- to configure via vivado hardware server `make .vconfig`
-- Cmod A7
+- [Cmod A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_cmoda7)
- connect USB cable to micro-USB connector
- to configure via vivado hardware server `make .vconfig`
-- Nexys4 and Nexys A7 (or Nexys4 DDR)
+- [Nexys4](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4)
+ and [Nexys A7](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexysa7)
+ (or
+ [Nexys4 DDR](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4d))
- connect USB cable to micro-USB connector labeled 'PROG'
- to configure via vivado hardware server `make .vconfig`
-- Nexys3
+- [Nexys3](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys3)
- use Cypress FX for configure and and rlink communication
- connect USB cable to micro-USB connector labeled 'USB PROG'
- to configure via FX2 and jtag tool `make .jconfig`
-- Nexys2
+- [Nexys2](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys2)
- connect USB cable to mini-USB connector (between RS232 and PS/2 port)
- to configure via FX2 and jtag tool `make .jconfig`
-- S3board
+- [S3board](https://wfjm.github.io/home/w11/inst/boards.html#digi_s3board)
- connect the USB-RS232 cable to the RS232 port
- connect a JTAG programmer (e.g. Xilinx USB Cable II) to JTAG pins
- to configure via ISE Impact `make .iconfig`
@@ -110,46 +116,44 @@ All examples below use the same basic setup
are in the indicated positions (SWI=...). The concrete boot script
name is given in the following sections
- - for arty over serial
+ - for [sys_w11a_arty](../rtl/sys_gen/w11a/arty/README.md) or
+ [sys_w11a_as7](../rtl/sys_gen/w11a/artys7/README.md) over serial
SWI = 0110 (gives console light emulation...)
ti_w11 -tuD,12M,break,xon @_boot.tcl
- **Note**: the arty w11a has currently only 176 kB memory (all from BRAMS!).
- u5ed works fine. XXDP, RT11 and RSX-11M should work.
- 211bsd will not boot, neither most RSX-11M+ systems.
-
- - for b3 over serial
+ - for [sys_w11a_b3](../rtl/sys_gen/w11a/basys3/README.md) over serial
SWI = 00000000 00101000 (gives console light display on LEDS)
ti_w11 -tuD,12M,break,xon @_boot.tcl
-
**Note**: the basys3 w11a has only 176 kB memory (all from BRAMS!).
u5ed works fine. XXDP, RT11 and RSX-11M should work.
211bsd will not boot, neither most RSX-11M+ systems.
- - for c7 over serial
+ - for [sys_w11a_c7](../rtl/sys_gen/w11a/cmoda7/README.md) over serial
ti_w11 -tuD,12M,break,xon @_boot.tcl
- **Note**: the c7 w11a has currently only 672 kB memory
+ **Note**: the c7 w11a has only 672 kB memory
(512 SRAM + 160 BRAM).
u5ed, u7ed, XXDP, RT11, RSX-11M and most most RSX-11M+ systems should work.
211bsd works only in the 'non-networking' configuration
- [211bsd_rpmin](../tools/oskit/211bsd_rpmin)
+ [211bsd_rpmin](../tools/oskit/211bsd_rpmin).
- - for n4 or n4d over serial
+ - for [sys_w11a_n4](../rtl/sys_gen/w11a/nexys4/README.md)
+ or [sys_w11a_n4d](../rtl/sys_gen/w11a/nexys4d/README.md) over serial
SWI = 00000000 00101000 (gives console light display on LEDS)
ti_w11 -tuD,12M,break,cts @_boot.tcl
- - for n2,n3 over fx2
+ - for [sys_w11a_n3](../rtl/sys_gen/w11a/nexys3/README.md)
+ or [sys_w11a_n2](../rtl/sys_gen/w11a/nexys2/README.md) over fx2
SWI = 00101100
ti_w11 -u @_boot.tcl
- - for s3 over serial
+ - for [sys_w11a_s3](../rtl/sys_gen/w11a/s3board/README.md) over serial
SWI = 00101010
ti_w11 -tu,460k,break,xon @_boot.tcl
@@ -158,7 +162,7 @@ All examples below use the same basic setup
- the letter after `-tu` is either the serial device number,
denoted as ``, or the letter `D` for auto-detection of
Digilent boards with a FT2232HQ based interface.
- - for Arty, Basys3, CmodA7 and Nexys4 board simply use `D`
+ - for Arty A7, Basys3, Cmod A7, Nexys4, and Nexys A7 board simply use `D`
- otherwise check with `ls /dev/ttyUSB*` to see what is available
- `` is typically '1' if a single `FT2232HQ` based board is connected,
like an Arty, Basys3, CmodA7, or Nexys4. Initially two ttyUSB devices
@@ -167,22 +171,22 @@ All examples below use the same basic setup
connection.
- `` is typically '0' if only a single USB-RS232 cable is connected
- - on LED display
- - is controlled by SWI(3)
+ - on LED display
+ - is controlled by SWI(3)
0 -> system status
1 -> DR emulation --> OS specific light patterns
- - on Hex display
- - is controlled by SWI(5:4)
- - boards with a 4 digit display
+ - on Hex display
+ - is controlled by SWI(5:4)
+ - boards with a 4 digit display
00 -> serial link rate divider
01 -> PC
10 -> DISPREG
11 -> DR emulation
- - boards with 8 digit display
+ - boards with 8 digit display
SWI(5) select for DSP(7:4) display
0 -> serial link rate divider
@@ -300,4 +304,5 @@ Several oskits are provided:
| [rt11-53_rl](../tools/oskit/rt11-53_rl) | RT-11 V5.3 | RL02 | |
| [xxdp_rl](../tools/oskit/xxdp_rl) | XXDP 22 and 25 | RL02 | |
-For further details consult the `README.md` file in the oskit directory.
+For further details consult the [README.md](../tools/oskit/README.md)
+file in the oskit directory.
diff --git a/rtl/sys_gen/w11a/arty/README.md b/rtl/sys_gen/w11a/arty/README.md
new file mode 100644
index 00000000..67cd79fd
--- /dev/null
+++ b/rtl/sys_gen/w11a/arty/README.md
@@ -0,0 +1,54 @@
+## Notes on w11 systems: w11a for Arty A7-35
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_arty](sys_w11a_arty.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Arty A7-35](https://wfjm.github.io/home/w11/inst/boards.html#digi_arty) board
+with DDR3 SDRAM support via a Vivado MIG core.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 32 kB |
+| Memory | 3840 kB from DDR3 SDRAM via [miglib_arty](../../../bplib/arty/miglib_arty.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+An alternative design that uses only BRAM is available as
+[sys_w11a_br_arty](../arty_bram).
+
+### Usage
+
+The board has only 4 LEDs plus 4 RGB-LEDS and offers only a compactified
+console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 0110 (gives console light emulation...)
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The Arty A7-35 board is one of the main w11 development platforms.
+The sys_w11a_arty design is often FPGA tested with
+[ostest](../../../../tools/bin/ostest) against all
+[oskits](../../../../tools/oskit).
+
+- **2019-06-05**: reduce clock to 72 MHz, Vivado 2919.1 fails with 75 MHz
+- **2019-01-27**: reduce clock to 75 MHz, Vivado 2918.3 fails with 80 MHz
+- **2018-11-18**: initial version, runs with 80 MHz using Vivado 2017.4
+
+
+
diff --git a/rtl/sys_gen/w11a/arty_bram/README.md b/rtl/sys_gen/w11a/arty_bram/README.md
new file mode 100644
index 00000000..ba13bca7
--- /dev/null
+++ b/rtl/sys_gen/w11a/arty_bram/README.md
@@ -0,0 +1,54 @@
+## Notes on w11 systems: w11a for Arty A7-35 (BRAM only)
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_br_arty](sys_w11a_br_arty.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Arty A7-35](https://wfjm.github.io/home/w11/inst/boards.html#digi_arty)
+board, where the w11 memory is based only on BRAMs.
+It was created before MIG support was completed, has reduced diagnostics
+(to save BRAMs), and is mainly useful for debugging and testing the memory.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 176 kB from BRAMs via [pdp11_bram_memctl](../../../w11a/pdp11_bram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: **no**; ibmon: **no**; dmpcnt: yes; dmhbpt: 2; dmcmon: **no** |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+A design with full SDRAM memory support is available as
+[sys_w11a_arty](../arty).
+
+### Usage
+
+The board has only 4 LEDs plus 4 RGB-LEDS and offers only a compactified
+console light emulation.
+The memory size of 176 kB allows starting a few
+[oskits](../../../../tools/oskit).
+u5ed works fine. XXDP, RT11 and RSX-11M should work. 211bsd will not boot,
+neither most RSX-11M+ systems.
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 0110 (gives console light emulation...)
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The Arty A7-35 board is one of the main w11 development platforms.
+The sys_w11a_br_arty design is occasionally FPGA tested with
+[ostest](../../../../tools/bin/ostest) against the
+[oskits](../../../../tools/oskit) running with 176 kB memory.
+
+- **2016-02-27**: initial version.
diff --git a/rtl/sys_gen/w11a/artys7/README.md b/rtl/sys_gen/w11a/artys7/README.md
new file mode 100644
index 00000000..ae29f863
--- /dev/null
+++ b/rtl/sys_gen/w11a/artys7/README.md
@@ -0,0 +1,48 @@
+## Notes on w11 systems: w11a for Arty S7-50
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_as7](sys_w11a_as7.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Arty S7-50](https://wfjm.github.io/home/w11/inst/boards.html#digi_artys7)
+board with DDR3 SDRAM support via a Vivado MIG core.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 32 kB |
+| Memory | 3840 kB from DDR3 SDRAM via [miglib_artys7](../../../bplib/artys7/miglib_artys7.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+An alternative design that uses only BRAM is available as
+[sys_w11a_br_as7](../artys7_bram).
+
+### Usage
+
+The board has only 4 LEDs plus 2 RGB-LEDS and offers only a very rudimentary
+console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 0110 (gives console light emulation...)
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The author doesn't have an Arty S7 board and doesn't plan to buy one.
+The design was made to study differences between Artix-7 and Spartan-7.
+The design is [only simulation tested](https://github.com/wfjm/w11/issues/17).
+
+- **2019-01-12**: initial version
diff --git a/rtl/sys_gen/w11a/artys7_bram/README.md b/rtl/sys_gen/w11a/artys7_bram/README.md
new file mode 100644
index 00000000..af5cfe85
--- /dev/null
+++ b/rtl/sys_gen/w11a/artys7_bram/README.md
@@ -0,0 +1,51 @@
+## Notes on w11 systems: w11a for Arty S7-50 (BRAM only)
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_br_as7](sys_w11a_br_as7.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Arty S7-50](https://wfjm.github.io/home/w11/inst/boards.html#digi_artys7)
+board , where the w11 memory is based only on BRAMs.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 256 kB from BRAMs via [pdp11_bram_memctl](../../../w11a/pdp11_bram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: **no**; ibmon: **no**; dmpcnt: yes; dmhbpt: 2; dmcmon: **no**|
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+A design with full SDRAM memory support is available as
+[sys_w11a_artys7](../artys7).
+
+### Usage
+
+The board has only 4 LEDs plus 2 RGB-LEDS and offers only a very rudimentary
+console light emulation.
+The memory size of 256 kB allows starting a few
+[oskits](../../../../tools/oskit).
+u5ed works fine. XXDP, RT11 and RSX-11M should work. 211bsd will not boot,
+neither most RSX-11M+ systems.
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 0110 (gives console light emulation...)
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The author doesn't have an Arty S7 board and doesn't plan to buy one.
+The design was made to study differences between Artix-7 and Spartan-7.
+The design is [only simulation tested](https://github.com/wfjm/w11/issues/17).
+
+- **2018-08-11**: initial version
diff --git a/rtl/sys_gen/w11a/basys3/README.md b/rtl/sys_gen/w11a/basys3/README.md
new file mode 100644
index 00000000..86efa75b
--- /dev/null
+++ b/rtl/sys_gen/w11a/basys3/README.md
@@ -0,0 +1,50 @@
+## Notes on w11 systems: w11a for Basys 3
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_b3](sys_w11a_b3.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Basys 3](https://wfjm.github.io/home/w11/inst/boards.html#digi_basys3)
+board. The w11 memory is based on BRAMs only because the board doesn't
+feature any memory outside the FPGA.
+
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 176 kB from BRAMs via [pdp11_bram_memctl](../../../w11a/pdp11_bram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: **no**; ibmon: **no**; dmpcnt: yes; dmhbpt: 2; dmcmon: **no** |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+### Usage
+
+The board has 16 LEDs and allows a nice console light emulation.
+The memory size of 176 kB allows starting a few
+[oskits](../../../../tools/oskit).
+u5ed works fine. XXDP, RT11 and RSX-11M should work. 211bsd will not boot,
+neither most RSX-11M+ systems.
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00000000 00101000 (gives console light display on LEDS)
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The Basys 3 board is one of the w11 development platforms.
+The sys_w11a_b3 design is regularly FPGA tested with
+[ostest](../../../../tools/bin/ostest) against the
+[oskits](../../../../tools/oskit) running with 176 kB memory.
+
+- **2015-02-08**: initial version.
diff --git a/rtl/sys_gen/w11a/cmoda7/README.md b/rtl/sys_gen/w11a/cmoda7/README.md
new file mode 100644
index 00000000..f34eb7c9
--- /dev/null
+++ b/rtl/sys_gen/w11a/cmoda7/README.md
@@ -0,0 +1,49 @@
+## Notes on w11 systems: w11a for Cmod A7-35
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_c7](sys_w11a_c7.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Cmod A7-35](https://wfjm.github.io/home/w11/inst/boards.html#digi_cmoda7)
+board.
+
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 16 kB |
+| Memory | 672 kB combined from 512 kB SRAM via [c7_sram_memctl](../../../bplib/cmoda7/c7_sram_memctl.vhd) and 160 kB BRAMs via [pdp11_bram_memctl](../../../w11a/pdp11_bram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+### Usage
+
+The board has no LEDs and thus no console light emulation.
+The memory size of 672 kB allows starting only a subset of the available
+[oskits](../../../../tools/oskit).
+u5ed, u7ed, XXDP, RT11, RSX-11M and most most RSX-11M+ systems should work.
+211bsd works only in the 'non-networking' configuration
+[211bsd_rpmin](../../../../tools/oskit/211bsd_rpmin).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ ti_w11 -tuD,12M,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The Cmod A7-35 board is one of the w11 development platforms.
+The sys_w11a_c7 design is regularly FPGA tested with
+[ostest](../../../../tools/bin/ostest) against the
+[oskits](../../../../tools/oskit) running with 672 kB memory.
+
+- **2017-06-24**: initial version.
diff --git a/rtl/sys_gen/w11a/nexys2/README.md b/rtl/sys_gen/w11a/nexys2/README.md
new file mode 100644
index 00000000..f00aad80
--- /dev/null
+++ b/rtl/sys_gen/w11a/nexys2/README.md
@@ -0,0 +1,48 @@
+## Notes on w11 systems: w11a for and Nexys 2
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_n2](sys_w11a_n2.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Nexys 2](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys2)
+board.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 3840 kB from PSRAM via [nx_cram_memctl_as](../../../bplib/nxcramlib/nx_cram_memctl_as.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | USB 2 speed over Cypress FX2 |
+
+### Usage
+The board has 8 LEDs and offers only a compactified console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00101100
+ ti_w11 -u @_boot.tcl
+```
+
+### Status & History
+
+The Nexys 2 board was, along with the Nexys 3 board, the main w11
+development platforms until the Nexys 4 board arrived and development
+moved from ISE to Vivado.
+Together with the Nexys 3 board, it still has the best I/O performance
+thanks to the USB 2 speed and low-latency rlink connection.
+The sys_w11a_n2 design is occasionally FPGA tested with
+[ostest](../../../../tools/bin/ostest) against all
+[oskits](../../../../tools/oskit).
+
+- **2010-05-28**: initial version
diff --git a/rtl/sys_gen/w11a/nexys3/README.md b/rtl/sys_gen/w11a/nexys3/README.md
new file mode 100644
index 00000000..ef7c82db
--- /dev/null
+++ b/rtl/sys_gen/w11a/nexys3/README.md
@@ -0,0 +1,47 @@
+## Notes on w11 systems: w11a for and Nexys 3
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_n3](sys_w11a_n3.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Nexys 3](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys3)
+board.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 3840 kB from PSRAM via [nx_cram_memctl_as](../../../bplib/nxcramlib/nx_cram_memctl_as.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | USB 2 speed over Cypress FX2 |
+
+### Usage
+The board has 8 LEDs and offers only a compactified console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00101100
+ ti_w11 -u @_boot.tcl
+```
+
+### Status & History
+
+The Nexys 3 board was the main w11 development platforms until the
+Nexys 4 board arrived and development moved from ISE to Vivado.
+Together with the Nexys 2 board, it still has the best I/O performance
+thanks to the USB 2 speed and low-latency rlink connection.
+The sys_w11a_n3 design is occasionally FPGA tested with
+[ostest](../../../../tools/bin/ostest) against all
+[oskits](../../../../tools/oskit).
+
+- **2011-11-20**: initial version
diff --git a/rtl/sys_gen/w11a/nexys4/README.md b/rtl/sys_gen/w11a/nexys4/README.md
new file mode 100644
index 00000000..ffa10f17
--- /dev/null
+++ b/rtl/sys_gen/w11a/nexys4/README.md
@@ -0,0 +1,48 @@
+## Notes on w11 systems: w11a for and Nexys 4
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_n4](sys_w11a_n4.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Nexys 4](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4)
+board.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 32 kB |
+| Memory | 3840 kB from PSRAM via [nx_cram_memctl_as](../../../bplib/nxcramlib/nx_cram_memctl_as.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+### Usage
+The board has 16 LEDs and allows a nice console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00000000 00101000 (gives console light display on LEDS)
+ ti_w11 -tuD,12M,break,cts @_boot.tcl
+```
+
+### Status & History
+
+The Nexys 4 board was the main w11 development platforms until it
+[failed in July 2019](https://wfjm.github.io/blogs/w11/2019-07-27-nexys4-obituary.html). Until July 2019 the sys_w11a_n4 design was often FPGA tested with
+[ostest](../../../../tools/bin/ostest) against all
+[oskits](../../../../tools/oskit). Since July 2019 this design is
+only simulation tested.
+
+- **2019-07-20**: board failed, from now on the design only simulation tested
+- **2013-09-22**: initial version
+
+
diff --git a/rtl/sys_gen/w11a/nexys4d/README.md b/rtl/sys_gen/w11a/nexys4d/README.md
new file mode 100644
index 00000000..4759487c
--- /dev/null
+++ b/rtl/sys_gen/w11a/nexys4d/README.md
@@ -0,0 +1,55 @@
+## Notes on w11 systems: w11a for Nexys A7-100 and Nexys 4 DDR
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_n4d](sys_w11a_n4d.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Nexys A7-100](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexysa7)
+board with DDR2 SDRAM support via a Vivado MIG core.
+The design is also compatible with the
+[Nexys 4 DDR](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4d)
+board.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 32 kB |
+| Memory | 3840 kB from DDR2 SDRAM via [miglib_nexys4d](../../../bplib/nexys4d/miglib_nexys4d.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+An alternative design that uses only BRAM is available as
+[sys_w11a_br_n4d](../nexys4d_bram).
+
+### Usage
+The board has 16 LEDs and allows a nice console light emulation.
+The memory size of 3840 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00000000 00101000 (gives console light display on LEDs)
+ ti_w11 -tuD,12M,break,cts @_boot.tcl
+```
+
+### Status & History
+
+The Nexys A7-100 board is one of the main w11 development platforms.
+The sys_w11a_n4d design is often FPGA tested with
+[ostest](../../../../tools/bin/ostest) against all
+[oskits](../../../../tools/oskit).
+
+- **2019-08-10**: procured Nexys A7-100 board. BUGFIX in MIG configuration.
+ Now fully [FPGA tested and verified](https://github.com/wfjm/w11/issues/16).
+- **2019-01-02**: initial version, only simulation tested (no board available
+ for FPGA testing)
+
+
diff --git a/rtl/sys_gen/w11a/nexys4d_bram/README.md b/rtl/sys_gen/w11a/nexys4d_bram/README.md
new file mode 100644
index 00000000..63595faf
--- /dev/null
+++ b/rtl/sys_gen/w11a/nexys4d_bram/README.md
@@ -0,0 +1,62 @@
+## Notes on w11 systems: w11a for Nexys A7-100 and Nexys 4 DDR (BRAM only)
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_br_n4d](sys_w11a_br_n4d.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[Nexys A7-100](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexysa7)
+board, where the w11 memory is based only on BRAMs.
+The design is also compatible with the
+[Nexys 4 DDR](https://wfjm.github.io/home/w11/inst/boards.html#digi_nexys4d)
+board.
+It was created before MIG support was completed, has reduced diagnostics
+(to save BRAMs), and is mainly useful for debugging and testing the memory.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 512 kB from BRAMs via [pdp11_bram_memctl](../../../w11a/pdp11_bram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: **no**; ibmon: **no**; dmpcnt: yes; dmhbpt: 2; dmcmon: **no** |
+| Rlink | 12 Mbps via FT2232HQ based serial link |
+
+A design with full SDRAM memory support is available as
+[sys_w11a_n4d](../nexys4d).
+
+### Usage
+
+The board has 16 LEDs and allows a nice console light emulation.
+The memory size of 512 kB allows starting only a subset of the available
+[oskits](../../../../tools/oskit).
+u5ed, u7ed, XXDP, RT11, RSX-11M and most most RSX-11M+ systems should work.
+211bsd works only in the 'non-networking' configuration
+[211bsd_rpmin](../../../../tools/oskit/211bsd_rpmin).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00000000 00101000 (gives console light display on LEDs)
+ ti_w11 -tuD,12M,break,cts @_boot.tcl
+```
+
+### Status & History
+
+The Nexys A7-100 board is one of the main w11 development platforms.
+The sys_w11a_br_n4d design is occasionally FPGA tested with
+[ostest](../../../../tools/bin/ostest) against the
+[oskits](../../../../tools/oskit) running with 512 kB memory.
+
+- **2019-08-10**: procured Nexys A7-100 board. Design is now fully FPGA
+ tested and verified.
+- **2017-01-04**: initial version, only simulation tested (no board available
+ for FPGA testing)
+
+
diff --git a/rtl/sys_gen/w11a/s3board/README.md b/rtl/sys_gen/w11a/s3board/README.md
new file mode 100644
index 00000000..98e050c2
--- /dev/null
+++ b/rtl/sys_gen/w11a/s3board/README.md
@@ -0,0 +1,46 @@
+## Notes on w11 systems: w11a for and S3BOARD
+
+- [Basics](#user-content-basics)
+- [Usage](#user-content-usage)
+- [Status & History](#user-content-status)
+
+### Basics
+
+The [sys_w11a_s3](sys_w11a_s3.vhd) system is a
+[w11a](../../../w11a) implementation for the Digilent
+[S3BOARD](https://wfjm.github.io/home/w11/inst/boards.html#digi_s3board)
+board.
+For complete configuration, see [sys_conf.vhd](sys_conf.vhd).
+The most important features are:
+
+| Property | Value |
+| -------- | ----- |
+| CPU options | FPP: no; Cache: 8 kB |
+| Memory | 1024 kB from SRAM via [s3_sram_memctl](../../../bplib/s3board/s3_sram_memctl.vhd) |
+| Devices | DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes |
+| Diagnostics | rbmon: yes; ibmon: yes; dmpcnt: yes; dmhbpt: 2; dmcmon: yes |
+| Rlink | 460 kbps via USB-RS232 cable connected to the RS232 port |
+
+### Usage
+The board has 8 LEDs and offers only a compactified console light emulation.
+The memory size of 1024 kB allows starting all [oskits](../../../../tools/oskit).
+
+For complete instructions on how to run operating system images,
+[see w11a_os_guide](../../../../doc/w11a_os_guide.md).
+The default setup is:
+
+```
+ SWI = 00101010
+ ti_w11 -tu,460k,break,xon @_boot.tcl
+```
+
+### Status & History
+
+The S3BOARD was the first w11 development platform. All inital w11
+developments were done with this board. In 2011, the developemt switched
+to the Nexys 2 board, as this board offered full 4 MB memory, and
+more importantly, a high speed rlink connection.
+The S3BOARD is still available, but is no longer actively used.
+The design is retained for historical and nostalgic reasons.
+
+- **2007-09-23**: initial version