Sunday, March 29, 2015

Sirius 1 Schematics

There are already some schematics for the Sirius available. However, I did not find schematics for all parts of the system online. Below you will find a pdf containing some (low quality) scans of schematics that I have collected over the years. Maybe that will help you with your maintenance and restoration projects.


Booting MS-DOS 3.1 on old Sirius 1 computers without the Universal Boot-ROM

Some internet sources claim that for booting MS-DOS 3.1 on the Sirius 1 the machine has to be equipped with the Universal Boot ROM or an ISSUE Boot ROM which is based on the Universal.

This is not the whole truth. Basically the only limitation in the original Boot ROM (also called P1 Boot ROM) that prevents it from starting DOS 3.1 is that it was only capable of loading operating
systems smaller than 64k. MS-DOS 3.1 has a size of >75k (Sirius 1 Version incl. BIOS).

The Boot ROM of the hard disk machines (at least the ones I have) are on the other hand already capable of loading system files >64k even without Universal Boot ROMs. This is due to the fact that the additional HD drivers often made even the old MS-DOS versions bigger than 64k. So these machines will boot 3.1 without any problem.

To overcome the 64k limitation for P1 ROM equipped machines I came up with a simple solution:

Sirius system files also contain the BIOS and one or two charsets. Especially the charset is very good compressable with RLE encoding. This led to the development of a runtime RLE decompression tool for the operating system. After compressing MS-DOS 3.1 its size was reduced to 60k. The compressed OS contains an extraction routine which extracts the orginal 75k system to RAM on-the-fly and then starts the OS. MS-DOS won't recognize the difference. This way 3.1 also starts from old Boot ROMs. Besides you will save some space on system disks due to the smaller file size. However, there will be no impact on the RAM requirements.

Basically this tool can be used to compress all MS-DOS versions for the Sirius. In general it would even work with CP/M-86 system files. So if you have the time, you could extract a CP/M-86 system file to MS-DOS, compress it, transfer it back to CP/M-86 and create a boot disk.

The tool including source code can be downloaded here. There is a compressed version of MS-DOS 3.1 for the Sirius 1 included (dos31rle.SYS), ready to use.


Welcome to my Sirius 1 Blog

Welcome to this blog dedicated to the vintage computer Sirius 1 / Victor 9000!

Compared to other vintage computers the information about the computer available in the internet is quite limited. Some of the information is even wrong, like several sources claiming the Sirius ran at 4.77 MHz like the IBM PC. In fact the 8088 in the Sirius was running at 5 MHz.

So the purpose of this blog is to publish more information about the Sirius 1 and the related systems:
- Sirius 1 / Victor 9000
- Victor Vicki
- Victor Sirius VI

I will also post some old school programming code snippets or tools that might be helpful for vintage computers or just to demostrate some fun stuff (mainly 8088 x86 Assembler).

As I am collecting as much information as possible about the Sirius, you are invited to send me your own documentation or software related to the Sirius and help me making it available to everyone.