bcw@rti.UUCP (Bruce Wright) (08/16/88)
In article <Added.oX0NFay00Ui3E4408M@andrew.cmu.edu>, GTHEALL@PENNDRLN.BITNET (George A. Theall) writes: > > Hi all! Another hardware question. Will the new 286-chip > replacement board for the Rainbow (soon to be released by Suitable > Solutions!!!) require faster memory chips? That is, won't the > processor speed be constrained by the access time of the memory > chips? With 256K of memory running about $100 these days, buying > new memory would add about 50% to the price of the 286 upgrade. > Actually you would have to replace the clock crystal too to do what you are proposing. You might also have to replace other chips on the boards depending on how well they worked with the new timings (memory is by no means the only chip which is sensitive to timing). I suspect that this sort of upgrade would not work on the Rainbow - there are problems in the BIOS which could cause a system with a constantly faster clock to refuse to boot. My understanding is that the problems are just with the ROM BIOS and only during the initial system startup (it is possible that it would still be possible to get the system up with error messages - I have heard conflicting accounts and have not tried it myself). I also suspect (but do not know for a fact) that the way the TurBow board (or however they are spelling it) works is by having a cache memory, and that the 80286 and cache are turned on by software. It would be possible to turn on a clock this way too (some PC clones do this), but there are so many potential problems that I doubt that they would do it that way - it would make for potential problems with some customers. Much safer to just make it cache memory and then you don't have obscure system failures when the faster clock kicks in. Bruce C. Wright