Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!yale!hsdndev!cmcl2!adm!smoke!gwyn From: gwyn@smoke.brl.mil (Doug Gwyn) Newsgroups: comp.sys.apple2 Subject: Re: Memory Expansion Apple IIgs Message-ID: <15414@smoke.brl.mil> Date: 10 Mar 91 20:32:46 GMT References: <9103032008.AA10465@apple.com> <1991Mar5.063335.13398@ux1.cso.uiuc.edu> Organization: U.S. Army Ballistic Research Laboratory, APG, MD. Lines: 28 In article <1991Mar5.063335.13398@ux1.cso.uiuc.edu> scotth@ux1.cso.uiuc.edu (Scott Henderson) writes: >The other alternative is the Octoram card for around $40 more. It will >hold up to 8 1 meg SIMMs. 4 megs of which are DMA compatible. As many >have pointed out to me, if you have the Apple High Speed SCSI, all 8 >megs are DMA. I have an 8MB OctoRAM and Apple's High-Speed SCSI card, as well as TWGS and FPE, all of which are fussy about DMA. The true story is that only the first 4 (of 8 total) SIMMs on the OctoRAM properly support DMA (due to an inherent IIGS design problem, not the OctoRAM's fault). The High- Speed SCSI Card detects when there is an attempt to transfer data to/from addresses above 4MB, and uses programmed I/O instead of DMA for those cases. This does NOT help when you use 8 256KB SIMMs in your OctoRAM, but it does when you use 8 1MB SIMMs. Another thing to worry about is that the Applied Engineering TransWarp/GS requires the latest PAL chips (TWGS-2B I think is the critical one) to work right with DMA devices, and both that PAL AND a TWGS hardware mod (lifting pin 1 of U22 as I recall) to work with Innovative Systems' FPE floating-point accelerator card. I will say that when one finally gets all this equipment working together it makes for a very nice set-up. (I also recommend configuring the upper 4MB as a RAM disk, to avoid ANY opportunity for DMA problems.) >Make sure that the dealer you buy it from has them in stock. Especially since the company that originally manufactured them (MDIdeas) has gone out of business. The OctoRAM's designer has been looking for another manufacturer.