RE: More CPLD explorations

Its probably not obvious how busy we were just trying to get the damm thing
to work and even then  _we would have had to bump one of the other chips
revision_ to rev the VIC. As it was, every day was a new emergency and then
manament would make up a few more.  I had 4-5 custom chips going through the
cycles and two got made incorrectly in a non-usable way just over small
tweaks. (The PLA shorted out its backbias ring, the MMU had its masks mixed
up at MOS)  My Gant chart was six pages tall, probably over 100 items on it.

So counting the time to get VIC change designed, laid out, PG'ed, and a run
from MOS ($$$) not that we have done without one of the other chip revs as
8563 took all slack out of the queues, there was no way we would have done
something like this.

 To restate, I had a huge list of real problems in spite of getting fixed
daily, and I wouldn't have re-decided to fix a problem that was not regarded
as a problem, the trixk with going this fast is make a decision and move on,
riskiest things were made less risky.  Again we didn't identify any
compatibility problems until we were in mass production and shipping.   Also
we had people canceling the real MMU, and evidently the C128D and also the
LCD machine and then I left, making it smell nice wasn't an option. >:)


-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Gerrit Heitsch
Sent: Tuesday, February 25, 2014 1:22 PM
To: cbm-hackers@musoftware.de
Subject: Re: More CPLD explorations

On 02/25/2014 07:07 PM, Bil Herd wrote:
> Yeah I remember the 3 seconds where I made the mistake on hiding the
> register in the VIC.  I thought to do a "lock the door and throw away
> the key" approach where only a cold start would bring it back in.

Judging from the schematics, the C128 has a signal (labeled '64/128') that
seems to tell some of the logic what mode it is in. That could have gotten
used together with an unused pin (which it has as far as I know) on the
48pin VIC to 'disappear' the registers in C64 mode.

That would also have prevented getting stuck with the registers gone in
C128 mode.



> But then we never said it was 100% compatible. >:)

That's why I wrote 'almost'. It was still impressive.

> (we had a LOT of 7406/7s)

So I see... and most of them from Russia (EL74xx).

  Gerrit



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