Re: Hardware emulation of 6509 using 6502?

From: Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de>
Date: Wed, 15 Nov 2017 12:48:05 +0100
Message-ID: <05792cc4-c389-5388-9b0e-7e84fde3b203@laosinh.s.bawue.de>
On 11/15/2017 12:44 PM, silverdr@wfmh.org.pl wrote:
> 
>> On 2017-11-15, at 12:23, didier derny <didier@aida.org> wrote:
>>
>> not sure the 6502 from wdc sold by mouser are a direct remplacement of the 6502 used on our commodore...
>>
>> I have a 6502 from wdc it never worked on any machine, apparently it needs an adapter for some signals...
> 
> AFAIR there are some pin differences with some extra signals and also GND.
> 
>> you got these fake 6502 from many sellers ? or from the same....
> 
> I bought it once from one seller. A larger batch. Tested a few randomly, using the test prg for the floppy, gpz (AFAIR) pointed me to and it showed only the slight difference on one (I think) illegal opcode, which was supposedly to be all fine. The discussion should still be in the archives. So the ugly bottoms of the chips aside things looked pretty much OK. Until I started to get some difficult to explain errors with some of my DD boards. It was not that they were some other chips relabelled. They were definitely working, but not reliably.

Illegal Opcodes were never guaranteed. If you want those to work, you 
have to stick to 6502 from MOS, everyone else might have made small 
changes to the mask or the process which caused some illegal opcodes to 
behave differently.

  Gerrit



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Received on 2017-11-15 12:02:30

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