Hi all,

A couple of months ago I was able to bring a PET 8296 back from the dead by
replacing a bad PLA with an EPROM containing the "readout" of the PLA, and a
pinout adaptor.

Is the same thing possible with the PLA in the C64/SX64?  (Part #
906114-01).  I assume it is, but I'm curious if anyone here has tried it
already.  I'm running low on 'real' PLAs, but have dozens of 27C512 EPROMs.

Also, is the C64 PLA readout available online?  I found where it *should*
have been on funet, but I'm guessing it was removed based on the ominous
disclaimer at the top of the page.

Thanks,
Leif

Leif Bloomquist wrote:

> Is the same thing possible with the PLA in the C64/SX64?  (Part #
> 906114-01).  I assume it is, but I'm curious if anyone here has tried
> it already.  I'm running low on 'real' PLAs, but have dozens of
> 27C512 EPROMs.

Yes. The idea first popped up in this newsgroup thanks to Spiro Trikaliotis, 
although apparently it seems it's a well known trick. Spiro, a couple of 
years ago, gave out the schematics in this newsgroup and a guy in my 
mailing-list ( http://groups.yahoo.com/group/cbmclub_main - check for 
details, if you can speak Italian <g> ) tried it out, succesfully.

> Also, is the C64 PLA readout available online?  I found where it
> *should* have been on funet, but I'm guessing it was removed based on
> the ominous disclaimer at the top of the page.

No, but you can find it on my mailing-list, in the files area. If you have 
problems, you can mail me, I'll send you the dump. I think Fabio Antimi 
hosts it on his homepage somewhere ( check it out, 
http://emulazione.multiplayer.it/cbmitapages/ ).

However, if you want my opinion, burning a PLS100 PAL it's a way better 
option :-)

Riccardo

Hi Leif
> Is the same thing possible with the PLA in the C64/SX64?  (Part #
> 906114-01).  I assume it is, but I'm curious if anyone here has tried
it
> already.  I'm running low on 'real' PLAs, but have dozens of 27C512
EPROMs.

No need to re-invent, done here:
http://emulazione.multiplayer.it/cbmitapages/tecnico/plaeng.htm

- Nick

Hi,
it's possible for details see my project. It seems to work really fine, like 
the original chip
http://emulazione.multiplayer.it/cbmitapages/
Greetings
Frilander 

Leif,

Some funet info is at

http://www.funet.fi/pub/cbm/firmware/computers/c64/pla.txt

Hodo


On 26 Feb 2005 19:50:53 -0800, "Nick @ 64HDD" <info@64hdd.com> wrote:

>Hi Leif
>> Is the same thing possible with the PLA in the C64/SX64?  (Part #
>> 906114-01).  I assume it is, but I'm curious if anyone here has tried
>it
>> already.  I'm running low on 'real' PLAs, but have dozens of 27C512
>EPROMs.
>
>No need to re-invent, done here:
>http://emulazione.multiplayer.it/cbmitapages/tecnico/plaeng.htm
>
>- Nick

Hallo Leif,

> A couple of months ago I was able to bring a PET 8296 back from the dead by
> replacing a bad PLA with an EPROM containing the "readout" of the PLA, and a
> pinout adaptor.

Very interesting because I have some dead 8296's laying around
suffering from dead PLA's. Is it paoosible to publish the used BIN's
and the pinout of the adaptor? Many thanks !!!

If the above works, the C64 must work as well as the 8296 runs on 2
MHz AFAIK, the C64 on 1 MHz. But maybe this could be of help as well:
what about using Flash RAMs? EPROMs are as fast as 150 ns.? FRAMs can
be as fast as 50 ns. Just an idea.


--
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   / /  |_/     Groetjes, Ruud
   \ \__|_\
    \___|       URL: Ruud.C64.org

"Ruud Baltissen" <Ruud.Baltissen@abp.nl> wrote in message
news:8b0a868e.0502280328.4480cd72@posting.google.com...

> Very interesting because I have some dead 8296's laying around
> suffering from dead PLA's. Is it paoosible to publish the used BIN's
> and the pinout of the adaptor? Many thanks !!!

Hi Ruud,

The .bins are here:
http://www.funet.fi/pub/cbm/firmware/computers/pet/8296/82s100.tar.gz

And the pinout of the PLA is here (a bit hard to read)
http://www.funet.fi/pub/cbm/schematics/computers/pet/8296/324644-6of9.gif

Regards,
Leif

"Frilander" <lmodoni@libero.it> wrote in message
news:_rhUd.53072$lB4.1446802@twister1.libero.it...

> it's possible for details see my project. It seems to work really fine,
like
> the original chip
> http://emulazione.multiplayer.it/cbmitapages/
> Greetings

That's perfect, exactly what I was looking for.  Thank you very much!

Regards,
Leif

Frilander wrote:
> Hi,
> it's possible for details see my project. It seems to work really fine, like 
> the original chip
> http://emulazione.multiplayer.it/cbmitapages/
> Greetings
> Frilander 
> 
> 
OK, what is on the sides of that PET:

http://emulazione.multiplayer.it/cbmitapages/pet/peteng.htm

Jim


-- 
Jim Brain, Brain Innovations
brain@jbrain.com                                http://www.jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!

Hallo Leif,

> The .bins are here:
> http://www.funet.fi/pub/cbm/firmware/computers/pet/8296/82s100.tar.gz
> 
> And the pinout of the PLA is here (a bit hard to read)
> http://www.funet.fi/pub/cbm/schematics/computers/pet/8296/324644-6of9.gif

Never noticed they were here. Many thanks!


--
     ___
    / __|__
   / /  |_/     Groetjes, Ruud
   \ \__|_\
    \___|       URL: Ruud.C64.org

"Frilander" <lmodoni@libero.it> wrote in message
news:_rhUd.53072$lB4.1446802@twister1.libero.it...

> it's possible for details see my project. It seems to work really fine,
like
> the original chip
> http://emulazione.multiplayer.it/cbmitapages/

I had a little bit of free time this weekend, and made up a little adaptor
following this pinout.  Also burned the .bin to a 27C512 EPROM.

The result works perfectly on a C64 Rev B board, but not on a Rev C board.
On the Rev C, it looks as though the character ROM is scrambled/missing
(characters are just garbage), yet this board works perfectly with the real
PLA installed.  The Rev C still boots fine, however, and cartridges that
define their own charset also work fine.

This really has me perplexed - any ideas anyone?

Thanks
Leif

On Mon, 14 Mar 2005 10:21:16 -0500, "Leif Bloomquist"
<spam@127.0.0.1301> wrote:

>"Frilander" <lmodoni@libero.it> wrote in message
>news:_rhUd.53072$lB4.1446802@twister1.libero.it...
>
>> it's possible for details see my project. It seems to work really fine,
>like
>> the original chip
>> http://emulazione.multiplayer.it/cbmitapages/
>
>I had a little bit of free time this weekend, and made up a little adaptor
>following this pinout.  Also burned the .bin to a 27C512 EPROM.
>
>The result works perfectly on a C64 Rev B board, but not on a Rev C board.
>On the Rev C, it looks as though the character ROM is scrambled/missing
>(characters are just garbage), yet this board works perfectly with the real
>PLA installed.  The Rev C still boots fine, however, and cartridges that
>define their own charset also work fine.
>
>This really has me perplexed - any ideas anyone?
>
>Thanks
>Leif
>

Everything else being equal, my guess would be that the PLA for Rev B
board is slightly different for Rev. C board in how it addresses
character ROM scan lines.

Or, character ROMS are slightly different between REV B & REV C
boards.

"Brian Lyons" <Nospam@nowhere.com> wrote in message
news:cldb31hjoge7q21pk96irlrgi5cdr1r9sh@4ax.com...

> Everything else being equal, my guess would be that the PLA for Rev B
> board is slightly different for Rev. C board in how it addresses
> character ROM scan lines.

I thought of that, but I can swap the PLAs between the Rev B and Rev C
boards without any noticeable difference.

Hello,

Leif Bloomquist <spam@127.0.0.1301> wrote:


> The result works perfectly on a C64 Rev B board, but not on a Rev C board.
> On the Rev C, it looks as though the character ROM is scrambled/missing
> (characters are just garbage), yet this board works perfectly with the real
> PLA installed.  The Rev C still boots fine, however, and cartridges that
> define their own charset also work fine.
>
> This really has me perplexed - any ideas anyone?

Or the garbaged characters always looking the same?

The biggest problem for replacing the PLA with an EPROM might be that a
PLA is built in such a way that there should be no spikes on the lines,
while with a(n) (E(P))ROM, this is not the case. Thus, there might be
spikes on arbitrary lines which prevent the EPROM from replacing the PLA
in an accurate manner.

Just some ideas,
   Spiro.

-- 
Spiro R. Trikaliotis
http://www.trikaliotis.net/

Hallo Leif,

> This really has me perplexed - any ideas anyone?

What about swapping the VIC's?


--
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   \ \__|_\
    \___|       URL: Ruud.C64.org

>I had a little bit of free time this weekend, and made up a little adaptor
>following this pinout.  Also burned the .bin to a 27C512 EPROM.

>The result works perfectly on a C64 Rev B board, but not on a Rev C board.

>This really has me perplexed - any ideas anyone?

EPROM may not be fast enough.

"Mika Leinonen" <mika.leinonen@tut.fi> wrote in message
news:d16k9d$e8s$1@news.cc.tut.fi...

> EPROM may not be fast enough.

Thanks, Mika, this appears to have been the problem!

I was using a 27C512 with 120ns response time before.  I replaced it with
one with 70ns response time, and it now works nearly perfectly.  I
occasionally see a small flicker in the character set, but nothing obvious.
So I guess that 70ns is still right on the edge.

Also, to correct my early post:  It's a Rev B board that shows this problem.
Rev C was OK with 120ns.

Regards,
Leif