Re: Adding DRAM to my IIGS' memory expansion board...

[spec@vax2.concordia.ca (Mitchell Spector)]

In article rubywand@aol.com writes...

>     According to our Memory Expansion Card Owner's Guide, there are two
>recommended upgrades:
> 
>512kB (top row filled-- 16 chips):      jumper on lower set of pins
>   1MB (both rows filled-- 32 chips):  jumpers on both sets of pins.
> 
> 
>     The manual says that the 768k upgrade (i.e., 24 chips on the card) is
>not a good idea "because some applications have trouble dealing with that
>configuration".

    Not only is this not a good idea, it will _not_ work. You cannot
populate half of the bottom row, you must fill both banks completely.
My old high school had their Apple IIgs memory board populated this
way, so that the card held 768K. Anything that tried to address this
memory crashed, at least until I disabled the lower bank of chips by
removing the upper jumper (imagine, if you will, a ROM 00, faulty VGC
chip and an inproperly configured memory board with a Disk ][ drive 
set as the startup device :). The only valid configurations for the 
card are: 256K (no chips installed), 512K and 1024K.

    Of course these days these cards are of little value, considering
1MB or less won't get you very far (although they are semi-useful in
a ROM 3, bringing it up to 2.125MB). With 4MB cards cheap and plentiful,
I'd faster purchase one than findle with finding chips for one of those 
limited old boards. :)

Mitchell Spector
spec@vax2.concordia.ca