• Please review our updated Terms and Rules here

Zimmers' BASIC2 ROMs

Witchy

Witchy

Experienced Member
Joined
Oct 11, 2015
Messages
376
Location
Flatlands, UK
Hi Folks,

After a lot of virtual hair tearing, desoldering, NOP generating and logic analysing on my PET2001-32N I've reached a question: Has anyone here actually put the BASIC2 ROM set from Zimmers in a UK 2001/3xxx machine? I ask because I don't have another machine easily available since my 3032 is next on the ToDo list and I'm baffled since neither the physical ROM set of:

901465-01 (UD6)
901465-02 (UD7)
901447-24 (UD8)
902465-03 (UD9)

or the BASIC2 side of my ROM/RAM board will boot in this machine - I just get a blank screen, no garbage, just blank. I've been reading a few things that say the 2xxx/3xxx non-CRTC video is 60hz only but surely that's just in the US?

Anyway, tonight I burnt a BASIC4 set with a non-CRTC 50hz editor (normal keyboard) and got a constant monitor prompt which means either the DIAG pin is pulled low on the user port or BASIC isn't starting. Buzzing out the previously unused ROM slot D5 showed a fault with one of the address lines so I removed the white socket and replaced it with a turned pin one like I've already done for D6/7/8/9. Success!

So, anyone? I suppose I could leave it at BASIC4...

Cheers :)

Witchy
 
Assuming your board is the same 'dynamic PET' board - assy. 320351, I have a PET with exactly that configuration of Basic-2 ROM's. It is possible that the ROM's on zimmers have not been read correctly. Maybe worth comparing them to the ones in VICE?

I don't think the 60hz/50hz question is relevant to non CRTC PET's. The vertical refresh frequency is fixed in hardware and the non-CRTC edit ROM's are not specific.
 
giobbi said:
I tested both BASIC2 and BASIC4 from Zimmers, both business and graphic keyboard, on my 3032, no problem at all.
Click to expand...

and thanks to Crock's suggestion I've just compared them to the VICE ROMs and they're the same. I'm now 100% baffled - there's 4 piles of ROMs in front of me:

the original set (health unknown)
2 sets of 2532JL-45 BASIC2 (one each with $E000 on a 2516JL-45 and 2716 ROM)
1 set of 2532JL-45 BASIC4 with $E000 on a 2716 (no CRTC, 50hz, normal keyboard)

Only the BASIC4 set works. Can anyone think of what else I can check? I should say that at all times in the ROM testing my ROM/RAM board has been providing the CPU and lower 16K of RAM.

Cheers!
 
I just looked through the schematics and parts list for the dynamic board and there isn't any obvious differences between basic 2 and basic 4. My only thought might be with the RAM. You said you have the lower 16k from your RAM/ROM board and yet it's a 32k machine, so I assume the upper 16k from the onboard RAM. Maybe there's some subtle RAM issue and how it's detected between basic 2 and basic 4? Have you tried mapping the whole 32k to the RAM/ROM board?
 
Witchy said:
and thanks to Crock's suggestion I've just compared them to the VICE ROMs and they're the same. I'm now 100% baffled - there's 4 piles of ROMs in front of me:

the original set (health unknown)
2 sets of 2532JL-45 BASIC2 (one each with $E000 on a 2516JL-45 and 2716 ROM)
1 set of 2532JL-45 BASIC4 with $E000 on a 2716 (no CRTC, 50hz, normal keyboard)

Only the BASIC4 set works. Can anyone think of what else I can check? I should say that at all times in the ROM testing my ROM/RAM board has been providing the CPU and lower 16K of RAM.

Cheers!
Click to expand...

I also had this kind of problem while I was repairing my 3032. Black screen with BASIC2, working with BASIC4. Then I discovered it worked with BASIC2, and the business keyboard edit rom (afaik 3032 came with the graphic keyboard only).
I patiently compared and mixed the hex code of the two edit roms, adding the differences to the business keyboard rom, once at a time, until I found the culprit: few hex bytes.
Somebody here at VCF told me to check a line on the board, and I discovered somebody in the past cut this line with a screwdriver when he removed a chip.... I fixed the pcb and everything began to work fine! I don't remember how many eprom I programmed during this test, LOL.

So, what I can suggest to you is to try the BASIC2 using the edit rom for business keyboard and see if it boots or not...


EDIT --- no need to use the old 2516... 2716 will work fine for the 2 kb ROM... of course you'll need an adapter for the 2732 eprom, though.
 
giobbi said:
Here's the thread about my days of trouble with BASIC2 vs. BASIC4...

http://www.vintage-computer.com/vcforum/showthread.php?37736-9-quot-CRT-vc-12-quot-CRT/page12
Click to expand...
Wow. It was me who noticed the difference between the business and graphics ROM's but I have absolutely no recollection of it. That's age messing with me...

So, next step would be to try the business basic-2 edit ROM and see if that works. The keyboard mapping will be messed up but you should get a display if indeed that is the underlying issue.
 
So as giobbi and crock discovered, an open signal at the VIA (C5-pin15) called Video On can cause the problem. Check the connection between C5-pin 15 and C7-pin18, also to the source at H10-pin11.

This was a left over circuit from the original design of the 2001-8 which only allowed writes to the screen during the vertical retrace period so 'snow' would not be seen on the screen. The 3032 and 4000/8000 PETs do not need to wait for the vertical retrace as the CPU updates the screen on the opposite phase of the clock as the screen refresh logic so there should not be any address contention as there was on the 2001-8 design. I think faster static RAM made the new design possible.
 
And this is why this place is such a goldmine of information! Oddly enough after my fun with the $B000 socket I was going to remove the rest of the white ones anyway - in my case it's more than likely a bad socket instead of a broken trace. This however means I may have 'fixed' it by stealth instead of understanding the real issue which is MUCH more entertaining to discover :D

I'm away visiting my lady so the first thing I'll do when I get back is burn a business edit ROM to see if that 'fixes' anything, typically I'm reading all this while over 4 hours away from the beast in question.

Oh, and Giobbi, I recognised your 3032 fix writeup you did - that picture of your 2732 ROM modification was the first thing I found when looking around for info to help fixing the first 4032 I attempted back in October, cheers!

Ta folks!
 
Hmm. I think there's still more to this...

I have another 4032 on my desk which has the dynamic board, graphics keyboard and basic 4 ROM's with the 901447-29 edit ROM. If I replace this with a set of basic-2 roms, it doesn't boot. It gets as far as clearing the screen, but then hangs, with both the graphics and business edit ROMS. I also took an edit ROM and made the changes that giobbi and I identified a couple of years ago and still no boot. This makes me think that there must be some other subtle modification to the board for those machines that were shipped with the basic-4 ROM's.

Witchy - do you think your machine was shipped with basic-4 ROM's?

Rob
 
crock said:
Witchy - do you think your machine was shipped with basic-4 ROM's?

Rob
Click to expand...

No, because there's only 4 in the set*, not 5, and the part numbers match the BASIC-2 set though this page has 901465-01/02 as BASIC-3 which puzzled me a while back. My ROM/RAM board from Tynemouth Software has Zimmers' BASIC2 set in it as well, and I know that works on a 4032 since I tested it last week. I don't know what Edit ROM Dave has put in there though, I'll email him tonight and ask.

The one thing I can't remember offhand is which board is in that 4032, pretty sure it's not the dynamic one though, because that definitely has subtle differences which I didn't notice until I was trying to find chips that were on the schematic I had but not on the board :)

(*This is a big assumption on my part that each flavour of BASIC also requires the matching Kernal and Edit (with sub-matches for keyboard type etc), so for example you couldn't run BASIC2 ROMS with a Kernal for BASIC4?)

Cheers!

W
 
crock said:
Hmm. I think there's still more to this...

I have another 4032 on my desk which has the dynamic board, graphics keyboard and basic 4 ROM's with the 901447-29 edit ROM. If I replace this with a set of basic-2 roms, it doesn't boot. It gets as far as clearing the screen, but then hangs, with both the graphics and business edit ROMS. I also took an edit ROM and made the changes that giobbi and I identified a couple of years ago and still no boot. This makes me think that there must be some other subtle modification to the board for those machines that were shipped with the basic-4 ROM's.

Witchy - do you think your machine was shipped with basic-4 ROM's?

Rob
Click to expand...

Not sure, but... 4032 should be a CRTC model, like the 8032 (I don't own a 4032, so I can't be sure). It could make a big difference, imho; afaik 8032 came with BASIC-4 set. I didn't test it with a BASIC-2 set.

However I have to say my error was strange and unique, I believe there's almost no chances that other machines can suffer the same problem. But it worth a try...
 
I think there's 3 different boards between my 4016/4032/8032/8096/8096-SK, the -SK is the only one I have that has the metal can* covering the crystal and the F-row which I think is the 'proper' dynamic board? It's also the only one I have that's made in HK with a simplified power circuit - only 2 regulators in the heatsink. The rest appear to be different models of 40 or fat 40.

(*well, should have, it's removed because of the power entry bracket)
 
Witchy said:
I think there's 3 different boards between my 4016/4032/8032/8096/8096-SK, the -SK is the only one I have that has the metal can* covering the crystal and the F-row which I think is the 'proper' dynamic board? It's also the only one I have that's made in HK with a simplified power circuit - only 2 regulators in the heatsink. The rest appear to be different models of 40 or fat 40.
Click to expand...
Hi Witchy, by convention, the "dynamic" board refers to the first board that used dynamic rams but before the CRTC chip was introduced. André Fachet has a nice summary of the different boards here. The dynamic board is the 2nd one.

Rob
 
crock said:
Hi Witchy, by convention, the "dynamic" board refers to the first board that used dynamic rams but before the CRTC chip was introduced. André Fachet has a nice summary of the different boards here. The dynamic board is the 2nd one.
Click to expand...

And the one with the CRTC is the "universal" board, if my memory is correct. Is it?

The one that came later, also with the CRTC, but with 128k must have a name too.
 
You must log in or register to reply here.
Back
Top