On 11/4/2021 10:43 AM, Francesco Messineo wrote: > On Thu, Nov 4, 2021 at 4:31 PM Jim Brain <brain_at_jbrain.com> wrote: >> I'm surprised they didn't use their >> internal 65XX RAM option (6550?) > basically 6550 were already an "old" thing by 1979. > Even the original 2001 motherboard had at least two revisions that > used 2114 instead of 6550. I guess I knew that, but forgot. > Using a 6550 instead of a 2114 for color ram on the C64 would have > been pointless anyway, since the big differences are just > the great flexibility in the CE choices (5 different CEs on 6550) vs. > one /CE on the 2114 and the bigger size of the 6550 (22 dip 400 mils). Oh, no argument there, but at Commodore, cost alone drove the discussion, not features (or too many of them). if they could get great yields out and not have to buy outside, the vertical integration could yield significant cost savings. So, the fact they used the 2114 in the 64 and the newer PETs suggests they were sourcing 2114s cheaper than it cost CBM to manufacture 6550s combined with the opportunity cost of tying up their fab space for that IC in lieu of using it for other ICs. Jim > > Frank IZ8DWF > -- Jim Brain brain_at_jbrain.com www.jbrain.comReceived on 2021-11-04 18:00:03
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