asd@mentor.cc.purdue.edu (Kareth) (01/18/89)
In article <9394@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes: [bunch deleted] >They also >mention something worth knowing about, namely DMA compatibility. >Some Apple II peripherals, including I think AST's VisionPlus >video digitizer, utilize Direct Memory Access to transfer data. >Due to lack of information out of Apple, most of the earlier >GS RAM cards did not address the proper locations when DMA was >in effect. (BY THE WAY: Does anyone know whether MDI OctoRAM >had this problem and how to upgrade if so?) Unless you're sure >you will never use a DMA peripheral (and how could you be sure?), >you should get a DMA-compatible card. (I think Apple's was OK.) As I recall, Apple gave the wrong information on development to vendors. Something about memory pointers and how to have them incremented (?). Anyways, A+ did a review about boards and the DMA capability a long time ago and if I remember correctly, the problems occured with more than 4Meg. A+ said that this problem could be taken care off as long as you don't have more than 4Meg of memory assigned for regular use. This means you'd have to assign anything over 4Meg to ramdisk usage. As for the OctoRAM, I have one with 2Meg. I've not heard if it is capable of DMA but I've not had any problems yet. One interesting note: the GSOS flasher (when you change sound levels, the border flashes) seems also to indicate memory problems in the ramdisk menu. When I'd recently upgrade my OctoRAM, I failed to get the SIMM chips fully socketed and was having problems booting GSOS. When I was changing the size of the ramdisk, I kept getting the flasher. Once I figured out the problem and fixed it, no flasher. Keith, is this a bug/feature or what? kareth.