RE: is there any easy way to upgrade a C116 to 64k

I am (pleasantly) surprised that _any_ of the units really work after 30
years given the history we had with some of the IC production (passivation,
ion implanter) and I don’t remember where the 7500 fell in whether it was a
finished design rule set or whether all  long-term bets are off unless
you're on the 8500. We also had to run several/many revs of the TED chip
just to get it working and so they had limited time in the end to tweak the
working design. (ERC and geometry checks were done by hand, DRC checks
wouldn’t catch an outright short)

The TED system lives with a certain amount of contention, I mentally rated
it at the time at about 20% contention at the time  as tristate buffers of
the day turned off much slower than they turned on so some portion of
current was likely to occur during the bus switchover.  We used to refer to
it as the bus heater effect meaning that we exchanged the die temperature
(and lifetime) for time to market and unit cost.

My memory on the smaller 16K systems was that it mapped over the 64k range
as no /CAS steering or gating was taking place. I would not think that
anything could contend with the DRAM safely if I read one of the previous
posts correctly. Also DRAM bus contention usually means DRAM contents
corruption.

I remember something being said by management to make sure that the smaller
machines weren’t easily upgradable but at the engineer level we didn't hold
too much regard as we had all heard the stories of the alienation that
drilling out the PET PCB's had done. I don’t think we could have gotten away
with anything where all you had to do was swap DRAM's, though 16Kx4's were
brand new at the time and 256k DRAMSs didn’t yet exist that I remember.

Regards,
Bil

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Michal Pleban
Sent: Wednesday, May 01, 2013 7:09 AM
To: cbm-hackers@musoftware.de
Subject: Re: is there any easy way to upgrade a C116 to 64k

Ted wrote:

> Does that apply to the Plus/4 also?

With regard to bus contentions with additional RAM, it's rather moot because
the Plus/4 already has 64kB of RAM ;-) But had it less, yes, it would be the
same.

With regards to fragility, yes, the Plus/4 is also an extremely fragile
machine. I have seen several of them die suddenly without any apparent
reason while I was typing some BASIC program.

Regards,
Michau.




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