# Prime 50-Series Emulator

## What Is This?

This is a software emulator for a minicomputer architecture sold
by Prime Computer from the early 70s through about 1993.  Prime's
initial business plan was to make systems compatible with the
Honeywell x16 family, which had then-recently been discontinued.
Prime extended the architecture heavily.

## Emulator History

Beginning in 2005, Jim Wilcoxson developed an emulator for Prime
Computer's 50-Series architecture.  The emulator originally ran on
the PowerPC architecture.  In late 2011, Jim ported it so it would
run on x86.  This entailed solving endianness issues (The 50-Series
is big-endian), as well as re-optimizing the code for performance
without the host processor having a large set of general-purpose
registers.

## Emulator Documentation

Coming soon, we swear!

## Public Systems

There are a set of emulators available for public use.  These may
be accessed via `telnet` to the appropriate port on `em.prirun.com`.

| PRIMOS Revision | Port |
|-----------------|------|
| 18.3.1          | 8007 |
| 19.2            | 8001 |
| 20.2.8          | 8002 |
| 21.0.6          | 8003 |
| 22.1.4          | 8004 |
| 23.4.Y2K.R1     | 8005 |
| 24.0.0.r15      | 8006 |

For example, `telnet em.prirun.com 8001`.

## Prime History

Some information about the Prime company is available in the FAQ
which was assembled by denizens of the comp.sys.prime usenet group
and Info-Prime mailing list around the time Prime's 50-Series
business unit ceased to exist.  A reformatted copy is available
[here](https://sysovl.info/reference_prime_faq.html).

## Prime Documentation

A growing collection of Prime and related documentation is available
at [sysovl.info](https://sysovl.info/reference_prime.html).  A howto
on installing PRIMOS in the emulator is [here](https://sysovl.info/reference_prime_drb_installing_primos.html).
Discussion of adapting these instructions to 22.1.4 has been occurring on the [cctalk mailing list](http://classiccmp.org/pipermail/cctalk/2020-March/052126.html).

## Getting PRIMOS

Two versions of PRIMOS are available from Bitsavers:

* [Rev 22.1.4](http://bitsavers.org/bits/Prime/primos_22.1.4.zip) [has issues]
* [Rev 22.1.4 repacked](https://yagi.h-net.org/m2214repack.tar.gz) [use this]
* [Rev 19.?](http://bitsavers.org/bits/Prime/pps/03_log.tape_I=boot_II=iptpal.tap.gz)

The Rev. 19 tape is a save from an installed system.

## Sample System Images

A set of sample system images derived from the public emulators can
be downloaded to get you started.  The 
[tarball](https://sysovl.info/pages/blobs/emulator/p50em_samplemachines_v4.tar)
is 143510751 bytes, and its sha256sum is 
f7bf880cb1c7f32903ad85c4f52386cf2179067b8bfcf2c10b51c2e4dcf074dd.
(gzip compression would only reduce this by ~400 kilobytes.)
V4 corrects ACL problems in the Rev19 and Rev24 images.

V3 removes additional junk, and rebuilds the disk images as 600 MB 
drives, split 30/10 heads filesystem/paging.  This tarball preserves 
sparse allocation ("holes"), so that uninitialized space in the disk 
images does not occupy actual space.  You may need to tell `tar` to 
preserve this sparse allocation when you extract, e.g. with the `-S` 
option.  Also includes enhancements to the wrapper scripts: directory 
independence and the ability to run the `runem` script from a terminal.