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wanted: DOS 1.0 RRIOT and ROM's

C

crock

Experienced Member
Joined
Jan 12, 2012
Messages
285
Location
Zurich, Switzerland
Hi All,

I was recently given a 2040 in really nice condition. As was the case with most that were in use when DOS 2.1 was released, it has had the ROM's and RRIOT upgraded. As I already have a pair of 4040's in good working order, I would like to 'downgrade' the 2040 to it's original buggy incarnation. I know I could burn a pair of eproms and but the RROIT on an adapter board to bypass the ROM but it would be nice to have the original chips. I'm sure there must of been hundreds of DOS 1.0 chips lying unused back in the day and I wondered if any of them found there way into your parts drawers?

In return I would offer a corresponding set of DOS 2.1 ROMS and RRIOT or anything else from my parts drawers that may be of use to people.

The DOS 1.0 and 2.1 part numbers and locations on the digital board are:

LocationDOS 1.0DOS 2.1
UL1901468-06901468-12
UK1-empty-901468-11
UH1901468-07901468-13
UK3901466-02901466-04

Cheers, Rob
 
crock said:
Hi All,

I was recently given a 2040 in really nice condition. As was the case with most that were in use when DOS 2.1 was released, it has had the ROM's and RRIOT upgraded. As I already have a pair of 4040's in good working order, I would like to 'downgrade' the 2040 to it's original buggy incarnation. I know I could burn a pair of eproms and but the RROIT on an adapter board to bypass the ROM but it would be nice to have the original chips. I'm sure there must of been hundreds of DOS 1.0 chips lying unused back in the day and I wondered if any of them found there way into your parts drawers?

In return I would offer a corresponding set of DOS 2.1 ROMS and RRIOT or anything else from my parts drawers that may be of use to people.

Cheers, Rob
Click to expand...
Let me have a look; I'll PM ya.
mike
 
crock said:
As I already have a pair of 4040's in good working order, I would like to 'downgrade' the 2040 to it's original buggy incarnation. I know I could burn a pair of eproms and put the RIOT on an adapter board to bypass the ROM but it would be nice to have the original chips.
Click to expand...

Hi Rob,
You really need the original ROMs as you can't use the 2532 EPROM in place of the 6332 type ROM in the 2040 board as pin 21 needs to be fixed at +5V in the 2532 (Vpp) while in the 6332, pin 21 is a positive going chip enable. Normally in the PET computer it is not used and fixed at +5V so there is no problem using a 2532 EPROM as substitute, but in the 2040 disk drive, pin 21 is connected to the Phase 2 clock. This is because in the 2040 there are two processors sharing the data bus and they each need to be disabled during opposite phases of the clock.

You could always kludge something like a 2764 EPROM to work using an adapter but you would not like how that would look.

So hopefully you can find the 30 year old ROM parts.
-Dave
 
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