I've been an Amiga user, and overall Commodore user, since the 80's and this is my first post to this board so I hope everybody finds it helpful.
Had my Amiga 500 with GVP A530 accelerator out lately and wanted to upgrade to a full 8M of RAM. After lots of searching on this board, and others, I found that getting the GVP 64-pin SIMMs these days was fairly difficult. And much like others I found GVP-M (
http://www.gvp-m.com/) less than helpful. I found this work (
http://aminet.net/package/docs/hard/gvpsim64) from Pascal Janin from the 90s which I'm sure a lot of you know. After reading that I thought to myself "I'm a EE with my own home lab, I can make these". So using Janin's work as a starting point and also using the 1M SIMM that originally came with my A530 I set off to work building my own.
Bare circuits boards:
Stuffed circuit boards:
Boards mounted in A530:
Even though I triple and quadruple checked everything I was fairly amped up when I applied power. If something went wrong its not like I can just go and buy another A530 at the store. Not only did it power on but booted in half the time with more fast RAM to use. Ran a battery of tests on them (checkerboard, walking ones, walking zeros, etc.) and everything passed. Ran some graphic animation programs and VR studio stuff to really exercise them with no issues.
I got the memory chips from Syracuse Semiconductors (
http://syracusesemiconductors.com/) via their eBay page (
http://www.ebay.com/itm/MT4C4001JDJ-...MAAOxy3zNSkmC4) for $2.50 a piece plus shipping. They are pulls but came in good shape and appear to be fully operational. The boards were ordered from a PCB manufacture that I use for production and prototype boards. Unfortunately those are the expensive pieces when orders in low quantity. I ordered 5 at $14.64 a piece plus shipping.
The attached ZIP file contains the schematic, gerbers, and a README with specifications and information. The project was designed in Protel 99SE. I freely release this information out into the wild in the hopes that others will find it helpful. Board assembly by hand wasn't bad. Normally, SOJ packages are fairly straight-forward as far as SMT parts go for hand placement, but since they are packed together closely on the board that added a little more difficulty.
I took one design liberty. The original SIMMs did not have any bypass/coupling capacitors. This was common for the time, not just with GVP, to save every penny. I added a 1/16" to the board height and placed pads for 0402 bypass capacitors. I rather have them and not need them, then need them and not have them. I've been testing without them and all is working well but their there for piece of mind.