On 3/8/21 7:21 PM, Mario Kienspergher wrote: > > Am 08.03.21 um 18:39 schrieb Jim Brain: >> On 3/8/2021 11:29 AM, Bill Degnan wrote: >>> Hi, >>> I have a strange C64C (I believe) motherboard with: >>> >>> PCB ASSY NO.250451 >>> PCB No. 251915 Rev.2 >>> >>> ...printed on it. I don't see this board documented in the normal >>> places and the PCB does not come up in a search, any ideas? The >>> VIC-II is missing. >>> >>> https://www.vintagecomputer.net/commodore/64C_250451/250451_251915_pic1.jpg >>> <https://www.vintagecomputer.net/commodore/64C_250451/250451_251915_pic1.jpg> >>> >>> >>> Thanks >>> >>> Bill Degnan >>> >> That's an odd one. Like a CR board, but with 8 DRAMs, though not ina >> 2x4 config like on the 466 board. >> > Indeed, looks like they were testing it but trashing it because of > problems, as the 250466 came much later with a NMOS VIC and old glue logic. > > IC-stampings are from mid/late '84. Maybe the HMOS-II-Version of the VIC > did not perform very well or the yield was too poor, or known problems > with other HMOS ICs (7501, 7360) forced postponing. They did use the 8500 on 250425 boards. Problems with VIC are possible, after all when the HMOS-II version came out, it was R2. And you can see on the right side that there is a space for a regulator (VR1), so the board might have been able to use an NMOS VIC. GerritReceived on 2021-03-08 20:04:06
Archive generated by hypermail 2.3.0.
