Re: Synertek 6502 compatibility

From: didier derny <>
Date: Thu, 12 Apr 2012 11:26:51 +0200
Message-ID: <>
it reminds me a bug in my old emulator...
I got almost the same message.

it was due to an error in my emulation of rol/ror or lsr.
I think it was impacting the normalization routine.

for the synertek component I dont really remember the bugs
but each time we had a strange problem we replace the synertek with a 
mos or rockwell component.

the sy6551 was really bugged and not generating the irq properly.

for the 6522 it was said that it was better to not use a synertek one....
I dont remember the reason...

I dont if these bugs have been fixed and when.


Le 12/04/2012 11:09, Anders Carlsson a écrit :
> Rob Clarke wrote:
>> I get "31653.4784 BYTES FREE" instead of 31743
> Although I haven't checked the code, I would imagine the memory count 
> internally uses FLPT format with FAC's on zeropage. Since your PET 
> otherwise works with a MOS CPU, it probably isn't a RAM problem. 
> Neither a bad address line on the 6502. Is it at all likely that the 
> startup code does something with decimal mode, which otherwise might 
> be rarely used and the Synertek 6502 then having an issue with decimal 
> mode?
> I think I have some loose SY6502 so eventually I could try it in some 
> PET or VIC, but not within the next few days.
> Best regards
> Anders Carlsson
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Received on 2012-04-12 10:00:40

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