Re: MAX Machine PLA

From: Segher Boessenkool <>
Date: Sun, 7 Aug 2016 15:07:37 -0500
Message-ID: <>
On Sun, Aug 07, 2016 at 03:52:22PM +0200, Gerrit Heitsch wrote:
> On 08/07/2016 03:04 PM, smf wrote:
> >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.
> Usually, MOS counted upwards, meaning the 6566 would have come before 
> the 6567. So either the static version came first or there was another 
> version, like a 6565. There are a few numbers missing between the 6561 
> (PAL-VIC for VIC-20) and the 6566 after all.

There seem to have been 6562/6563 and 6564/6565 projects as well.  Both
didn't pan out.

> >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).
> I read somewhere, that the PLA was used to allow starting the PCB design 
> before all the logic was ready. With the PLA you could make the PCB and 
> have a 28pin socket waiting for the guys who did the logic.

The PLA, being current mode, is also a lot faster than MOS.  The 7700/8700
go to quite some length to be faster.  See


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Received on 2016-08-07 21:00:07

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