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 donít 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 wouldnít 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 werenít 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 donít 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 didnít yet exist that I remember. Regards, Bil -----Original Message----- From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Michal Pleban Sent: Wednesday, May 01, 2013 7:09 AM To: email@example.com 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. Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2013-05-01 14:00:03
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