TRS-80 Model II/16A (Long Board) "Burst Mode" PAL Upgrade

[dlightman]

Even though it wasn't supported by Tandy the original 68000 "long" or "dog-eared" CPU board could be upgraded to support the DMA BURST Mode feature needed to run XENIX 3.x. You can actually find a lot of info out there that it was done but for whatever reason nobody ever documented the specifics.

Since the original CPU board is the most prolific of all the 68000 boards and XENIX 3.x is such a huge improvement over TRS-XENIX I very much wanted to see this modification resurrected. Lucky for us a long board with the burst mode modification made its way to me. I dumped the PALs, documented the modifications and successfully applied them to one of my own stock long boards.

The modification is very simple to do and easy to reverse without permanent modifications to your board.

Here is archive with everything needed to perform the modification: https://bit.ly/34DaHQu

Picture of the board I modified:

 

[bladamson]

Great work!!! Thank you for your efforts!!!

 

[Tarkie101]

Woot! Omg!

 

[Tibs]

Another thank you sir.

 

[Tibs]

Hey, works great with original disks. Nice work and thank you.

 

[spt87a]

The bit.ly archive link no longer works - what's the actual location of it? I've looked around the Model II and TRS-XENIX archives but haven't found it.

 

[spt87a]

Oop - never mind - that link does work. It is an anonymous FTP link so let it open WinSCP or whatever FTP app you have installed.

 

[shirsch]

The "long board" also fits fine in an M16B. Clearance between the card and rear door is tight, but ISTR getting it to fit. The card hold-down brackets must be omitted for this to work.

 

[dlightman]

Oop - never mind - that link does work. It is an anonymous FTP link so let it open WinSCP or whatever FTP app you have installed.

Here are the direct links:

http://major.butt.care/mirrors/Tandy%20Radio%20Shack%20Software/6mhz%20Long%20XENIX%203%20Upgrade.zip

http://major.butt.care/mirrors/Tandy%20Radio%20Shack%20Software/6mhz%20XENIX%203%20Upgrade.zip

Also a the XENIX 3.3 Upgrade with the burst mode checks patched out:

http://major.butt.care/mirrors/Tandy%20Radio%20Shack%20Software/OldPal_XNX330UPv3.HFE

http://major.butt.care/mirrors/Tandy%20Radio%20Shack%20Software/OldPal_XNX330UPv3.IMD

Use it in conjunction with the patched 3.2 from the model2archive to upgrade to 3.3:

model2archive/Software/Xenix/700-3039 - XENIX Multi-User Operating System/v03.02.00/Custom/6Mhz at master · pski/model2archive

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