Adventures in Retrocomputing: Troubleshooting a GS-RAM Plus

One of the outstanding items on my IIGS checklist has a bigger RAM card, because while 4mb is nice, I want to be able to push this thing to its limits. Fortunately, I’ve recently come a bit closer to completing the checklist. I sourced a 6MB Applied Engineering GS-RAM Plus for about $100 – a very reasonable price for a card like that, especially considering that the seller said that the card was tested to be in good working condition.

So, I bought the card, got it home and tried it in my IIGS – no luck. A little bit of research suggested that a GS-RAM plus would not work correctly on a ROM 03 IIGS if it had the 1A version of the GAL instead of the 1B version. This one, of course, had the 1A version. So, I popped it out, pulled my ROM 01 IIGS out from under the desk and tried it on that one. No luck there either. Got the same “checkerboard” screen on both machines, which can apparently indicate RAM or CPU problems, improperly seated chips, or a bad add-in card. Since the machine was working both before I installed the new RAM card, and after I took it out, I figured that it must be the culprit. So, I took a closer look:

m_45738_1As you can see, the chip right above the connector, on the left, has a hole in it. (This is the eBay seller’s original picture, so it must have happened in between the testing and the listing.) That, to me, looked like a likely culprit.

So, I contacted the eBay seller, asking their permission to try and fix the problem myself before returning the card ( – they were an absolute pleasure to work with) and set out to find a replacement chip. Fortunately, just about every chip on that card is socketed (a nice feature of late 80’s technology), so it would be easy to replace.

The trick, of course, is finding the right one. The hole was right in the middle of the model number on the chip, rendering the middle two characters unreadable – so I had to find another source of information. The product manuals were of no help, being mostly concerned with how to install the card. So, the next best option was to find a picture of the card (which appears to have gone through a couple of revisions) in a high enough resolution that I could read the model number off the chip. I busted out a little Google-fu, and eventually found this image kindly uploaded by the folks over at ReactiveMicro:

GS-RAM Plus - 6 Meg Board ShrunkFortunately, it was a GS-RAM Plus of the correct vintage, and the picture was high enough resolution to make a positive identification of the chip (The full sized picture is huge! 6068px × 2028px and 10MB – it was easy to read the fine print on all of the chips).

Now that I had a model number, the next step was to find out what the chip actually did. Fortunately, it was an off the shelf part (made by Samsung) and Google makes finding datasheets easy. With the datasheet in hand, I was able to determine that it was designed to be used in “implementing buffer registers, I/O ports, bidirectional bus drivers, and working registers.” Or, in other words, it would not contain any custom program logic or configuration, so can be easily replaced.

Fortunately, these are still readily available, so I checked out a few chip suppliers. Unfortunately, they all wanted me to buy in quantity, so it was back to eBay. I tracked one down for $1.78 plus shipping and had it sent out. It got here a few weeks later, arriving last night, and I swapped it out, plugged the card into the IIGS, and everything booted up just as expected.

It’s always nice when the problem ultimately turns out to be simple, even if it takes a bit of Internet spelunking to figure out the details!

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