RE: PET II questions (P500, B128, B256)

From: Chandra Bajpai (
Date: 2001-12-12 13:49:57

Sounds like I'm screwed here since I've got 6540 ROMS...the ROM I'm need
is the left most...(It think it the $F000 block).  There is signs
someone tried to fix it by using a daughter board with 2716 or
2708...Stupidly I accidentally removed a jumper that I believe provided
the chip select line. It sounds like this mod would have not worked

If anyone comes across a $F000 6540 I'll pay a reward/finders fee!


-----Original Message-----
[] On Behalf Of William Levak
Sent: Tuesday, December 11, 2001 4:50 PM
Subject: RE: PET II questions (P500, B128, B256)

On Mon, 10 Dec 2001, Chandra Bajpai wrote:

> I have a dead 2001 that has a bad ROM...Can anyone help with
> old Commodore ROM parts?  What EPROMS would make suitable

There are no substitutes for 6540 ROMs.

2316 ROMs can be replaced with either a 2516 or 2716 EPROM, but this
not work in all cases.  It is better to remove both 2316 ROMs in a 4K 
block and replace them with one 2532 (not 2732) EPROM which can be
in either of the original 2316 sockets.  

2332 ROMs can be replaced with 2532 (not 2732) EPROMs.

Just for completeness:

2364 ROMs can be replaced by Motorola 68764 or 68766 EPROMs, except in
IEEE disk drives where they will not work because of timing differences.

23128 and 23256 ROMs are completely compatible with 27128 and 27256

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