Scott wrote: > Now that I've got a working 64C, what would you recommend changing in the > defected 64C. the Processor (6510), PLA or both? Ray Carlsen writes: "Unlike the one in the C64, the PLA in the C64C runs cool to the touch. I've never seen a bad one. Of course new and old versions are not interchangeable. The older 6510 MPU seems to work in the C64C as a sub for the 8500. I have tried an 8500 in an old C64 and it worked (diagnostic test only), but I don't know how well these chips interchange in actual use. All of the 8500 series chips run cooler than the older 6500 series." http://personalpages.tds.net/~rcarlsen/cbm/c64cdiag.txt It seems remarkable if the 906114-01 (82S100) PLA in the breadbox C64 very often breaks but the 251715-01 (LH5062B, YM3535) PLA in the newer C64C almost never breaks. It should be fairly easy to construct a test program which swaps Basic, Kernal and Char ROMs in/out and see exactly what causes the machine to crash. This program should be written in machine code, possibly entered as DATA statements: SEI LDA $01 AND #$FE ; disable Basic ROM STA $01 INC $D020 LDA #$37 ; default value STA $01 CLI RTS 10 DATA 120,165,1,41,254,133,1,238,32,208,169,55,133,1,88,96,-1 20 I=679 30 READ A:IF A>0 THEN POKE I,A:I=I+1:GOTO 30 40 SYS 679 To disable Kernal, I suppose you replace 254 by 253. To switch in Character ROM you replace 41,254 by 9,2 (ORA #$02). Please correct me if I made any mistake here. I don't know if there is any need to check the data direction register at $0000, would programs often change it? Good luck! -- Anders Carlsson Message was sent through the cbm-hackers mailing listReceived on 2009-11-03 14:00:04
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