At 06:41 18/01/2003, Ethan Dicks wrote:
>--- Adrian Vickers <avickers_at_solutionengineers.com> wrote:
> > I dug the 2001 out of the cupboard the other day...
>
>Can you give more information about *which* 2001 you have? There
>are at least two major motherboard revisions for the static-RAM PETs.
>They use different ROMs and RAMs.
OK, I can but try....
According to the sticker on the back, this is a 2001-8BS. The motherboard
layout appears to be the same as the one pictured on www.zimmers.net on the
4k/8k layout. I've taken some photos of my motherboard, which can now be
found here:
http://helmies.org.uk/images/cbm2001/mobo_front.jpg
http://helmies.org.uk/images/cbm2001/mobo_back.jpg
http://helmies.org.uk/images/cbm2001/mobo_side.jpg
NOTE: Each picture is approx 449K = long download over a modem!
>Also, as I have one, there are also models of 2001 that have _dynamic_
>RAMs. My 2001-N has 32K worth of 4116 chips (from the factory) and a
>full-sized graphic keyboard. If it were for sale in Europe, it would
>most likely been labelled a 3032, for comparison, but here in the States,
>it says "2001" on the front.
>
>I bring it up because I _think_ you are talking about the original
>chicklet-keyboard SRAM PET, but you didn't come right out and say so.
Apologies, I didn't; I keep forgetting that the 2001 went through more
development than perhaps any of the other PETs. Yes, it is a chicklet
keyboard version, with static RAM (2114's) and original 28-pin MOS ROMs.
>
> > 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...
> >
> > 1) Can the BASIC ROM be swapped with one from, say, a 3032 or 4016?
>
>Most likely not. If your 2001 has 2114 SRAMs, perhaps. There are
>upgrade ROMs (BASIC 2.0, anyway) _for_ the 2001
Personally, I'd rather keep this one as original as possible, i.e. keep the
original (buggy) ROMs. However, if it means keeping it working, then I'm
prepared to substitute the MOS ROMs with a board/set of boards containing
more modern EPROMs wired appropriately containing the original images. Not
that I've got a clue how to go about doing that, mind...
> > In fact, which one IS the BASIC ROM?
>
>BASIC lives in several ROMs, the Kernel lives in several ROMs. BASICs
>prior to 4.0 occupied $C000-$DFFF, and the Kernel occupied $E000-$FFFF,
>minus the PIAs and VIAs, etc., at $E800. BASIC 4.0 starts at $B000
>to add room for diskette commands.
>
>In my PET, $9000, $A000 and $B000 are filled with user-supplied firmware
>(better machine-language monitor, BASIC extensions and a tape speeder).
>These sorts of things, plus ROMs for word processors and other applications
>were somewhat typical amongst serious PET users. Dunno if yours has
>anything like that, but if you find ROMs where you expect none to be,
>that's probably why.
Well, there are no unpolulated sockets, so perhaps it's a fair bet that
there's some extra stuff in there. Goodness knows what, though, all the
ROMs are MOS 6540's.
> > 2) If it's a dodgy memory chip, what's the best way of isolating it? I
> > have an oscilloscope, but nada skill in this sort of thing.
>
>The typical way of testing RAMs in a C= service center was to rotate
>a pair of them from bank to bank and see if the symptoms shift. It
>was especially handy for detecting zero page problems.
Figures :( I've had to do this once already to locate a broken 2114 (when
I got the machine, it claimed only 1600 bytes of memory were free).
Luckily, I have one more spare 2114 (I got two from someone on this list, I
forget who [for which I apologise] and thank them (again) profusely, as if
it is a broken 2114, there's a chance the second spare might be essential).
Anyway, if it *is* a failing RAM chip, my guess is it's the one which sits
near the bottom of BASIC memory, since the first line number causes a
crash. Does anyone have a map showing the correlation between memory
addresses & specific chips?
If it's on the schematics, I'll be looking there next (so no need to answer
that question).
<snip the rest for brevity>
Ta for that, all good info!
Thus, the order of the day is:
1) Try to determine which 2114 chip might have gone bad, either by
sequenced swapping or by trying to be clever with the schematics.
2) If that doesn't fix it, re-seat all ROMs.
3) If that doesn't fix it, go to plan C - which doesn't exist yet...
Also, I know this has been asked & answered before, but what's the best way
of cleaning the board? It has more dust on it than I am properly
comfortable with, and besides it looks horrible.
I'm guessing that *ideally* it should be washed in distilled water with a
very soft brush, then left in a warm place to dry thoroughly. OTOH, maybe
alcohol would be a better idea? I have some disc head cleaning alcohol
which would suffice - recommendations please!
>Good luck,
Thanks - I'm going to need that (in place of specific skills :)
>P.S. - if you don't know about http://www.funet.fi/pub/cbm/ it's a
>great site with schematics and firmware.
I already knew of it, but had forgotten how useful it might be. Will check
that out next. Ta!
--
Cheers, Ade.
Be where it's at, B-Racing!
http://b-racing.com
Received on Sat Jan 18 2003 - 06:53:03 GMT
