🚀 go-pugleaf

In article <1492@sputnik.COM> moriarty@tc.fluke.COM (Jeff Meyer) writes:
>A friend tells me that something needs to be jumpered on the Mac+ board so
>that the other 2M can be accessed, and he frowned on the possiblity of a
>2.5MB combination.  Two questions for you hardware people, or people who
>have installed Dove upgrades WITH the 1 Megabyte cards (eight or nine chips
>per card): Is 2.5 MB an impossibility?  And what jumpered operations need to
>be made to get a Mac+ to recognize that other 2MB? (This is the one I REALLY
>want to get an answer to).

There are two spots on the Mac Plus and Mac SE motherboards that you
have to fool with in order to get different memory combinations.  In
the SE, they are just above the SIMMs, and in the Plus they are (I
believe) near the mid-to-upper left edge with the SIMMs at the bottom.

The allowed combinations are 0.5 MB, 1 MB, 2 MB, 2.5 MB, AND 4 MB.
The two spots are labeled "One Row" and "256K".  Normally, the "One
Row" spot is empty, and the "256K" spot has a 150 ohm resistor.  If
you want 2.5 MB or 4 MB, replace with 1 Meg SIMMs the SIMMS in the
slot nearest the CPU (the bottom one) for 2.5 MB or in both slots for
4 MB and remove the resistor in the 256K spot.  I just clipped one end
and left the thing hanging there in case I wanted to easily resolder
it.

If you want 0.5 MB or 2MB, you have to solder a 150 ohm resistor into
the spot marked "One Row" and put one pair of SIMMs into the slots
nearest the CPU, leaving the other slots empty.

On the Mac II, you don't need to fiddle with resistors.  You do have
to replace the SIMMs in sets of four, giving possibilities of 1, 2, 4,
5, and 8 MB with 256Kb and 1Mb SIMMs.  I can hardly wait for 4Mb SIMMs
and a 32MB Macintosh (full color frame buffers take a lot of memory).

Stew Rubenstein
Cambridge Scientific Computing, Inc.
UUCPnet:    seismo!harvard!rubenstein            CompuServe: 76525,421
Internet:   rubenstein@harvard.harvard.edu       MCIMail:    CSC