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Path: news1.icaen!news.uiowa.edu!news.physics.uiowa.edu!math.ohio-state.edu!howland.erols.net!cam-news-hub1.bbnplanet.com!news.bbnplanet.com!cpk-news-hub1.bbnplanet.com!newsfeed.internetmci.com!status.gen.nz!news.express.co.nz!actrix.gen.nz!dempson From: dempson@actrix.gen.nz (David Empson) Newsgroups: comp.sys.apple2 Subject: Re: Hacking GS memory card? Date: Fri, 7 Feb 1997 20:57:58 +1300 Organization: Empsoft Lines: 34 Message-ID: <19970207205758321397@dempson.actrix.gen.nz> References: <5ddo00$81f@balsam.unca.edu> NNTP-Posting-Host: dempson.actrix.gen.nz X-Newsreader: MacSOUP 2.2b6 Rhonda K. Faircloth <RKFAIRCLOTH@unca.edu> wrote: > I've been poking around Apple's 1meg memory board for the //gs, trying > to increase it's memory capacity... hopefully to 4meg. Anybody have > any experience/knowledge in gs memory handling? Yep. I have the IIgs hardware reference, and I'm quite familiar with how standard memory cards are implemented (the more oddball ones are somewhat of a mystery). > I desolered the eight dram chips already on the board and ran some wires > to a socketed 256k SIMM on a proto-board. This tested ok. I then tacked a > wire to the unused FRA9 (pin3) line, ran that through the same type of > inverter/resistor (as the other address lines are handled) and brought it > to A9 of a 1meg simm. It would only give me 768k.d You have missed an important step. There is a pin on the memory slot which tells the motherboard what size of RAM is installed on the card. The Apple IIgs Memory Expansion Card is set for 256KB rows, so the motherboard doesn't use FRA9, and the row address lines decode into multiples of 256KB. If the appropriate pin is set for 1MB RAM then FRA9 contains the next multiplexed address bit, and the row address lines decode into multiples of 1MB. The pin in question is called MSIZE. It is pin 27 on the slot connector. It is unconnected for a card with 256KB rows, connected to ground for a card with 1MB rows. -- David Empson dempson@actrix.gen.nz Snail Mail: P.O. Box 27-103, Wellington, New Zealand