PET 2001 oddity

From: Adrian Vickers <avickers_at_solutionengineers.com>
Date: Sat Jan 18 06:54:33 2003

At 11:37 18/01/2003, you wrote:

>On Jan 17, 18:18, Adrian Vickers wrote:
> >
> > Unfortunately, the PET seems to have developed an odd fault: It won't
>take
> > a BASIC program, and some keywords seem to be knackered...
>
> > So.... I figure the BASIC ROM has become slightly corrupted, OR I've got
>a
> > flakey memory chip which reads OK but doesn't write properly. The
>question
> > is, how to find out?
>
>Swap some of the RAM chips around and see if it makes a difference. If it
>does, particularly if it fixes it, swap them back -- it might just be a bad
>socket contact. Be careful with the RAM chips: if you have the type of PET
>I think you do, they're MOS Technology 6550, aka unobtainium, and unlike
>any other RAM chip.

Hi Pete,

It's not *quite* as bad as all that, it uses 2114's. Although they're not
made of unobtainum, they ARE made of "rareium" (or R_at_RE!ium on eBay -
probably the *WOW* *L_at__at_K* isotope, knowing my luck :).

> > 1) Can the BASIC ROM be swapped with one from, say, a 3032 or 4016? In
> > fact, which one IS the BASIC ROM?
>
>No. BASIC (and also the rest of the code, whether you call it a kernel or
>a monitor, or "stuff") is spread over several chips.

Damn, I just *knew* it wouldn't be that easy.

> And in the early
>PETs, the ROMs too are MOS Technology specials, and the different versions
>of PETs had different ROMs.

AFAICT, these are version 1 ROMs. Every socket is filled, and they're all
MOS6540s.

>If it's got 28-pin MOS Technology MPS6540 ROMs, you'd need a carrier to
>shuffle some signals, at the very least, and possibly some logic to handle
>the multiple select lines.

Harrumph. Guess which one it has...

Still, I've no fear of making carriers, etc. - albeit time constraints &
lack of equipment will make it tough right now - at least until I can get
my MicroMAT going.

>The good news, though, is that I have a
>chicklet-keyboard 2001-N as well, and if necessary, I could probably do a
>ROM dump for you (though IIRC it used to be on the 'net somewhere). I
>wouldn't need to move more than a few hundreweight of stuff to get at it
>;-)

That might be cool (and *snap* about the tons of stuff, although having
seen your little collection I think you do have rather more to shift about
than me!). However, let me try out the RAM swapping & chip re-seating
first, and if that doesn't fix it, then we'll look into EPROMs & suchlike.

-- 
Cheers, Ade.
Be where it's at, B-Racing!
http://b-racing.com
Received on Sat Jan 18 2003 - 06:54:33 GMT

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