0fbbc0070c
* Import unmodified USE!UMBS source. From https://forum.vcfed.org/index.php?threads/loading-dos-high-on-a-xt.32320/ * Customize the UMB Driver prompts. * Refactor memory management. Allow activation of EMS/UMB on demand. * Update the XTEMM and XTUMBS drivers to map their ranges. * Add instructions for all the drivers.
131 lines
6.3 KiB
Markdown
131 lines
6.3 KiB
Markdown
# XTMax Device Drivers
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## BIOS Extension ROM for SD Card (BootROM)
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The XTMax maps a BIOS Extension ROM at address 0xCE000-0xCE7FF, plus a bank of registers at address 0xCE800-0xCEFFF.
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The BIOS Extension ROM presents the SD Card on the Teensy as a fixed disk drive that can be used for booting and/or for
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storage in MS-DOS and other operating systems using INT13h fixed disk services (note: OS/2 does not use INT13h fixed
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disk services and therefore cannot use the SD Card).
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The ROM can be relocated by changing the address `BOOTROM_ADDR` in the [`bootrom.h`](../Code/XTMax/bootrom.h) and
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re-deploying the Teensy sketch. The address **must** be a multiple of 2048 bytes (2KB) and must be within the range
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0xC8000-DF800 (this is the range that the BIOS searches).
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### Preparing an SD Card for use with MS-DOS
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The preferred method for preparing an SD Card for use is to use the machine with the XTMax. From an MS-DOS prompt, begin
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with re-writing the Master Boot Record (MBR) onto the SD Card. This is needed in order to make sure that the SD Card can
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be used for booting. Modern devices are shipped pre-formatted with an MBR that is not compatible with older x86
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micro-processors.
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```
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A:\> FDISK /MBR
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```
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Next, partitions can be created on the SD Card with `FDISK`.
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```
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A:\> FDISK
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```
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If there is another fixed disk drive, be sure to select the correct drive from the `FDISK` menu. The existing partition
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on the SD Card must first be deleted, before creating a new Primary Partition. **This will destroy the entire content of
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the SD Card**. The new Primary Partition must be set as Active if the SD Card must be used for booting.
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The partition on the SD Card will now appear as a new logical drive, typically `C:` or `D:` depending on availability.
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Finally, the partition must be formatted. Use `FORMAT` and use the `/S` switch if the SD Card must be used for booting.
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Note: MS-DOS will typically limit a partition size to 2GB. However, it is possible to create 3 additional Extended
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Partitions to increase the usage of the SD Card. These partitions will appear as new logical drives, such as `E:`, `F:`,
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etc... depending on availability.
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## MS-DOS Driver for SD Card (XTSD)
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This driver is provided as a back-up option for machines without support for BIOS Extension ROMs. It is based on the
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[SDPP](https://github.com/nilseuropa/sdpp) driver originally written by Robert Armstrong and later improved by Dan
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Marks.
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**This driver is not necessary when the BIOS Extension ROM is loaded by the BIOS during boot.**
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The device driver can be found here: [`XTSD.SYS`](https://raw.githubusercontent.com/MicroCoreLabs/Projects/master/XTMax/Drivers/XTSD.SYS).
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Once downloaded, it must be placed on a drive accessible during boot and must be invoked from `CONFIG.SYS` as shown in
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the example below:
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```
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DEVICE=A:\XTSD.SYS
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```
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When loaded, the driver will create a new logical drive for the SD Card, typically `C:` or `D:` depending on
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availability.
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### Preparing an SD Card for use with MS-DOS
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The SD Card can be prepared from another machine. In this example, the SD Card is prepared from a Windows 10/11 machine.
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Use `DISKPART`. First, use `LIST DISK` to find the disk number of the SD Card then `SELECT DISK #` with the appropriate
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disk number.
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Next, use `CLEAN` to delete all partitions. **This will destroy the entire content of the SD Card**.
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Finally, create a new partition with `CREATE PART PRIMARY SIZE=#` by specifying the desired partition size in MB.
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Depending on the version of MS-DOS on the machine that will be using the SD Card, there are limit on the size (typically
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2048 ie 2GB).
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The partition must be formatted, for example with `FORMAT #: /FS:FAT /Q`.
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## EMS Driver for MS-DOS (XTEMM)
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This driver provides LIM 4.0 Expanded Memory (EMS) through the [PSRAM](https://www.pjrc.com/store/psram.html) on the
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Teensy. It is based on the LoTech [`LTEMM.EXE`](https://www.lo-tech.co.uk/wiki/LTEMM.EXE) driver and inspired by work by
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Alex Tsourikov and Michael Karcher. Note that while the driver is compliant with EMS 4.0, it does not support memory
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back-filling.
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The device driver can be found here: [`XTEMM.EXE`](https://raw.githubusercontent.com/MicroCoreLabs/Projects/master/XTMax/Drivers/XTEMM.EXE).
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Once downloaded, it must be placed on a drive accessible during boot and must be invoked from `CONFIG.SYS` as shown in
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the example below:
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```
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DEVICE=A:\XTEMM.EXE /N
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```
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The address of the memory window used by the EMS driver is 0xD0000-0xDFFFF by default and can be changed with the `/P`
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argument. For example, to use segment 0xE000 (mapping to 0xE0000-0xEFFFF), the syntax is as follows:
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```
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DEVICE=A:\XTEMM.EXE /P:E000 /N
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```
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## UMB Driver for MS-DOS (XTUMBS)
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This driver provides Upper Memory Blocks (UMBs) in unused regions of the Upper Memory Area (UMA). It is based on the
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`USE!UMBS` driver originally written by Marco van Zwetselaar and later rewritten by Krister Nordvall and published on
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the [VCFED forum](https://forum.vcfed.org/index.php?threads/loading-dos-high-on-a-xt.32320/).
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The device driver can be found here: [`XTUMBS.SYS`](https://raw.githubusercontent.com/MicroCoreLabs/Projects/master/XTMax/Drivers/XTUMBS.SYS).
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Once downloaded, it must be placed on a drive accessible during boot and must be invoked from `CONFIG.SYS` as shown in
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the example below:
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```
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DEVICE=A:\XTUMBS.SYS D000-E000
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```
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In the example above, the memory region at 0xD0000-0xDFFFF will be used as an UMB. **Care must be taken to not conflict
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with other memory regions used by periperals or other drivers.** For example, the region at 0xD0000 may also be used
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by the EMS driver, and both drivers shall not be configured to conflict with each other.
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The XTMax can create UMBs at any address within the 0xA0000-0xEFFFF range. The only restriction is that the address and
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size of the UMB must be a multiple of 2048 bytes (2KB).
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The `XTUMBS` driver can accept several ranges for UMBs, as shown in the example below with two distinct ranges:
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```
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DEVICE=A:\XTUMBS.SYS A000-B000 D000-E000
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```
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**Note that the XTMax only enables RAM for the UMBs upon loading the `XTUMBS` driver. Therefore, tools such as
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[`TEST!UMB.EXE](https://raw.githubusercontent.com/MicroCoreLabs/Projects/master/XTMax/Drivers/TEST!UMB.EXE) cannot be used to
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identify available UMBs.** Instead, the user must identify the unavailable ranges (such as video RAM or ROMs) with tools
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like CheckIt! and determine which ranges are safe to use as UMBs.
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