jamesk Posted January 12, 2011 Share Posted January 12, 2011 I just finished building a 4Meg RAM card for my IIgs. It works great! It cost me $20 total ($9 for the card and $9 for 4x 30pin SIMMs). It took me about 8 hours to complete spread over three days, but it was great fun. The hardest most time consuming part was desoldering. My old 1Meg card should be up for sale soon. Quote Link to comment Share on other sites More sharing options...
+remowilliams Posted January 12, 2011 Share Posted January 12, 2011 Neat, that is very cool. I took the easy way out with a Sirius 8MB one. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted January 12, 2011 Share Posted January 12, 2011 So you modded a 1 meg card? I'm guessing that's what the resistor and four blue wires are for. Nice hacking there. Quote Link to comment Share on other sites More sharing options...
madmax2069 Posted January 12, 2011 Share Posted January 12, 2011 (edited) Wow nice, i always wondered if this was possible. i need to find another card to try this, don't want to run into the chance of ruining my 1 meg card that came with my IIgs. I could go the easy way and buy a 4 meg card from briel Edited January 12, 2011 by madmax2069 Quote Link to comment Share on other sites More sharing options...
Hatta Posted January 12, 2011 Share Posted January 12, 2011 That's really cool! This may be a dumb question, but how does it work. If the card is expecting 1meg, you can't just dump 4 meg on it and expect it to work right? What do you have to change to make it work with 4 meg? Quote Link to comment Share on other sites More sharing options...
jamesk Posted January 12, 2011 Author Share Posted January 12, 2011 That's really cool! This may be a dumb question, but how does it work. If the card is expecting 1meg, you can't just dump 4 meg on it and expect it to work right? What do you have to change to make it work with 4 meg? Here's the page with the Schematic. http://www.apple2pl.us/ How this works is explained in the Apple IIgs Hardware Reference starting on page 49. Page 52 under Extended RAM Mapping says "If the MSIZE pin is tied to ground (for 1-megabit RAMs). The FPI multiplexes 20 address bits onto RA0 through RA9 and generates the CROW0 and CROW1 row selects for rows of 1 MB.". Looking at the Schematic you will see that pin 27 is tied to ground. RA9 is now connected to UA18. RP2 is filled so a 33Ohm resister is added (RA). Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted January 13, 2011 Share Posted January 13, 2011 I found a dead webpage that was fortunately completely spidered by archive.org. These images should tell you all you need to know. The important thing is that the ram card slot was designed to support 1 megabit DRAM addressing. All you need is to steal an unused gate on the board for the extra address line. Quote Link to comment Share on other sites More sharing options...
jamesk Posted January 13, 2011 Author Share Posted January 13, 2011 The far VCC pins are coupled to ground. I didn't do this on my board. I don't know if that is necessary or just a good idea. Quote Link to comment Share on other sites More sharing options...
jamesk Posted January 13, 2011 Author Share Posted January 13, 2011 The important thing is that the ram card slot was designed to support 1 megabit DRAM addressing. All you need is to steal an unused gate on the board for the extra address line. Also note that the resistor array doesn't have enough pins so you have to add a 33Ω resistor. Quote Link to comment Share on other sites More sharing options...
jamesk Posted January 19, 2011 Author Share Posted January 19, 2011 Update: "Works Great" means "Fails at odd times" Did some poking around and I guess 2 and 3 chip SIMMs are out for the IIgs. You need 8 or 9 chip SIMMs. WHOOPS! I've got some new SIMMs on order and will try those out once they get here. Quote Link to comment Share on other sites More sharing options...
jamesk Posted February 3, 2011 Author Share Posted February 3, 2011 I will be installing my 3rd quartet of SIMMs in my IIgs tonight. The last group had 3 SIMMs that were 60ns chips when I ordered 70s. Finally I got four matching pairs of THM91000AS-80 Toshiba chips. I can actually find a datasheet for these! They are listed as 80ns CAS before RAS, so I am pretty confident they will be compatible. Quote Link to comment Share on other sites More sharing options...
Hatta Posted February 3, 2011 Share Posted February 3, 2011 I thought speed ratings on DRAMs were only guaranteed minimum access times. Can't you run a 60ns chip at 70ns? Quote Link to comment Share on other sites More sharing options...
jamesk Posted February 3, 2011 Author Share Posted February 3, 2011 I thought speed ratings on DRAMs were only guaranteed minimum access times. Can't you run a 60ns chip at 70ns? You would think so, I was following the advice in this thread: http://www.techtalkz.com/apple/187768-simm-compatibility-apple-iigs-ram-cards-potential-faq-addition.html It's been my experience that anythingfaster than 70ns is hit or miss. Also be sure that the speed of all of the simms is close, particularly adjacent pairs being equal. If anyone has an explanation I'd love to hear it. Quote Link to comment Share on other sites More sharing options...
jamesk Posted February 6, 2011 Author Share Posted February 6, 2011 So far so good. The new memory has passed testing a few times. I'm going to let it run for a while though. In case anyone tries this in the future, here are some tips. 30 pin SIMMs 8 or 9 Chip (preferably CAS before RAS no faster than 70ns These are the SIMMs I bought: http://www.memoryx.net/1mbx981.html They say they are HYB511000A-80 but I got Toshiba I've already replaced the IIgs battery with 3 AAA. I think the next job will be adding stereo sound. http://home.swbell.net/rubywand/R004STEREO.GIF Quote Link to comment Share on other sites More sharing options...
Hatta Posted February 6, 2011 Share Posted February 6, 2011 How do you do the battery replacement? I forget, does the IIgs use a CR2032 or a 1/2AA like compact macs do? And that stereo board, does IIgs software actually output two channels? Quote Link to comment Share on other sites More sharing options...
jamesk Posted February 6, 2011 Author Share Posted February 6, 2011 How do you do the battery replacement? I forget, does the IIgs use a CR2032 or a 1/2AA like compact macs do? And that stereo board, does IIgs software actually output two channels? The IIgs takes a 1/2AA 3.6V. The early models use a 1/2AA with leads, my ROM 3 had a 1/2AA battery holder. All you need to do is desolder the old battery or holder and solder in a x3 AAA battery holder. The sound chip on the IIgs is an Ensoniq ES5503. It is capable of producing 8 channel stereo. Virtually all IIgs software produces stereo sound. However on the IIgs the stereo jack outputs only mono. So in order to get stereo you have to demultiplex the signals from J25. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted February 9, 2011 Share Posted February 9, 2011 I hate those batteries, and I'm a Mac guy. They're lithium, but they seem to only last about a year. When there's a power failure, my MDD "Windtunnel" G4 doesn't turn itself back on if the battery is dead. Quote Link to comment Share on other sites More sharing options...
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