Re: MAX Machine PLA

On 07/08/2016 13:38, Gerrit Heitsch wrote:
> The interesting part would be to compare the 6566 and 6567 dies to see 
> what was changed and how much is the same. Where did they squeeze in 
> the refresh counter, the RAS/CAS logic, were things moved around for 
> it...
>

Apparently the 6567 shows that the dram logic was squeezed in round the 
edges, as if the chip was designed for static ram first. However, I 
heard that someone had de-capped the 6566 and it showed the dram logic 
was there but hacked out. I didn't see it myself and I'm asking round to 
see if anyone can stump up the goods.

It may have gone:

1. develop static ram chip because it was easier and drams were expensive.
2. develop dram chip and fix bugs/change timing to allow dynamic ram.
3. take the fixed chip and make a static ram version out of it again, so 
that it was as close to the dram version as possible.

AFAICT they originally planned to make a dram version for the P500 and 
the static ram version only happened when the ultimax project picked up 
the chips but they needed to make it cheaper.

The 6509 appears to have been made for the P500 and the 6510 for the 
ultimax. The c64 on the other hand was then just thrown together with 
the chips they had (hence the PLA).


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