bulkow@puff.wisc.edu (David Bulkow) (10/08/87)
A question for Commodore: Is it possible to use the 1764 memory expansion module with the SX-64 without a great deal of modifications to the SX power supply? I realize that the heavy duty power supply was included because the C-64 power supply would not be able to handle the extra board. -Dave
fred@cbmvax.UUCP (Fred Bowen) (10/13/87)
In article <1018@puff.wisc.edu>, bulkow@puff.wisc.edu (David Bulkow) writes: > A question for Commodore: Is it possible to use the 1764 memory expansion > module with the SX-64 without a great deal of modifications to the SX > power supply? I realize that the heavy duty power supply was included because > the C-64 power supply would not be able to handle the extra board. > -Dave Officially the 1764 cannot be used with the SX-64. In practice, however, there is _usually_ no problem doing so. There are two problem areas to investigate: 1. Power consumption. The SX-64 has a bigger supply than the C64, but just enough bigger to handle the built-in disk drive. In fact, the SX-64 was originally designed to accomodate 2 drives, but the power supply was just adequate for one. In the SX-64's I've tried here the power appeared adequate and caused no problem. 2. Timing differences. The SX-64 has a different PCB and along with that comes the inevitable timing diffs that spell trouble for the critical timing specs associated with the DMA operation. In the SX-64's I've tried here, the 1764 did not work because of this. However, the 1700/1750 expanders did work, apparently because the timing, which was tweaked for the C128 by populating R4, was shifted in a happy direction. Now, my attempts to use the expanders in the SX-64 have not been very exhaustive and certainly not very analytical. Your mileage may vary. I recommend, speaking as a hacker now, that you find a dealer (or friend) willing to let you try it. Further, my 'experiments' suggest you go for a 1700 or 1750 and not a 1764. You could always plop a resistor into R4 of a 1764, but since you cannot use the power supply anyhow why not save the $$$$ (or spend it on the extra RAM instead)? I'd be interested in hearing from others who may have tried this. Good luck, and let me know how it goes... you're on your own! -- -- Fred Bowen uucp: {ihnp4|rutgers|caip}!cbmvax!fred arpa: beats me tele: 215 431-9100 Commodore Electronics, Ltd., 1200 Wilson Drive, West Chester, PA, 19380