kraut@ut-emx.UUCP (Werner Uhrig) (03/01/88)
Question: can you configur a 2.5 Meg Mac+ with 256k chips *ONLY* ? what jumper-configuration is required? Details: Given a Mac+ upgraded to 2Meg using a MacMemory upgrade in the following configuration: a) a carrier-board for the 4 old 256K SIMMs ( = 1 Meg RAM ) b) a baby-board with 32 256K chips ( = 1 Meg RAM) c) a jumper which, attached between pin 11 and 12 of the CAS-chip at E3 (or between pin 11 of CAS at E3 and ground=right side of capacitor C18 above BMU2 at E2) represents "ONE ROW OF RAM ONLY" (note, that 2 SIMM-slots are considered "one row"; i.e. the Mac+ has 2 rows of 2 SIMMs each) the 2 boards with 1 Meg of memory in 32 chips of 256k each are installed in ROW 1 (next to the 68000) and the second ROW is empty. the jumper is installed, and the resistor-jumper "256k RAMs only" is in-place (as it comes from the factory; i.e. it is not cut out, as Tech Note 176 would require you to do if you were installing 2 1-Meg SIMMs based on 1Meg Ram-chips) Problem: I have some extra 256k SIMMs which I'd like to install in ROW 2 for a total of 2.5 Meg ..... but I'd need to know a jumper configuration that will work; (I have tried with and without the "ONE ROW OF RAM ONLY" jumper, which did not work; but before I cut out the "256 ONLY" resistor, I'd sure wished someone would assure me that that is the problem's solution. I can't help the feeling that there is no solution, but ..... )