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

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

In article Randall Smith <tigermtn@i-link-2.net> writes...

>Help! I've filled my memory expansion board and my GS is still only
>detecting 256K (512K total, 256K on logic board and 256k soldered unto
>the expansion board). Do I need to tell the computer I've added the
>dram? Maybe change a jumper someplace? 

    Yes, you need to use jumpers to tell the board which sockets have
been filled. You'll find the pins at the far end of the board, above the
gold connector fingers (labeled J1 and J2). Place a jumper on the lower
pins (J2) if you fill the top row of sockets. The upper pins (J1) tell 
the card the bottom two sockets are filled. If the entire card is filled
then both pins must be closed with a jumper.

    After that, the computer will automatically see the extra memory.
You can do a quick check by looking at the 'Largest selectable' size
in the "RAM Disk" Control Panel.

>The dram I added matches the stuff that's soldered on, 41256c 150ns. 
>I can't seem to get to to work. Any help would be great.

    They also must use CAS-before-RAS (Column Address Selection -before-
Row Address Selection) refreshing. The speed should be 150 nanoseconds
or faster as well. A couple of brands and chip production batches of
256Kx1 DRAMs were affected by the CAS-before-RAS problem, check and 
make sure you do not have any of the following:

- OKI chips marked "M41256-15" made in Japan with the date code 
  "6Y043" stamped on the chip. 

- Samsung chips marked "KM41256-15" made in Japan. 

- NEC chips that have "UK" stamped beneath the company name. Or any 
  with "Japan" and "P" as the first letter in the date code.

Some of these "faulty" chips may be soldered in on some Apple IIgs
Memory Expansion boards (I think it was NEC chips), so check those too.
Going by memory, I think it was boards manufactured in late 1987 until
early 1988 that were affected. Apple did free upgrades, but I wouldn't
expect that offer is still available today. :)

In any case, this problem would most likely cause crashing and other
oddities. Your problem sounds like you simply forgot to close the
jumper pins (a bit of foil or metal wire will do too, but a plastic 
jumper is always more reliable and safer).

Mitchell Spector
spec@vax2.concordia.ca