Re: 6502 Bug Information

["Sheldon Simms" <sheldonsimms@yahoo.com>]

On Thu, 03 Jul 2003 18:14:06 +0000, Bryan Parkoff wrote:

>     I use word fixed and random.  Fixed means that 6502 always sets 0 or 1
> to N and Z flags wrong according to what 6502 wants.  Random means that 6502
> never sets 0 or 1 to N and Z flags BEFORE or AFTER ADC/SBC execution.  It is
> like LDA sets 0 or 1 to N and Z flags before ADC/SBC while flags are never
> updated by ADC/SBC.
>     Am I correct according to BCD bug?

I believe you are correct if you are asserting that the 6502 does NOT
set N and Z flags randomly during BCD operations. It sets them wrongly,
but not randomly

The question is whether ALL 6502s set the N and Z flags the same during
BCD operations. It might be the case that (for example) newer 6502s set
the N and Z flags differently than older ones, although both set them
incorrectly.

That's the question you should be asking.