CompuServe Messages

John, this is a very complex question but I'll try to answer it: Lets say you have an Amiga 200 and want the fastest system using 2 MB RAM, a fast processor and a super harddrive. Lets say you want to make a VIDEO application. As the blitter and the rest of the chipset is using DMA it would not be too good for the system, if the harddisk would access the systems memory via DMA as well (perhaps you know of the problem using the CBM 2090 controller that has DMA and having an interlaced, overscan… screen on top). Let's say you still like the systemspeed and now think of using a fast processor- accellerator like CSA 68020 with 2 MB SRAM or DRAM (32 bit wide). As CSA does not handle their 32 bit wide memory for DMA access the CPU likes to move the data from the 2090 to the memory BUT the 2090 wants DMA. This could cause the whole system to slow down and it can get slower that just using the 2090 without the fast CPU! 1. NEVER use a DMA-controller for graphics, video or whatever that is going down to the SER:, PAR:, blitter using DMA as well. 2. NEVER use a DMA-controller together with a fast CPU (or even RAM) that does not support DMA. The best results would be using the 2620 with max. 4MB of DMA'd RAM and the 2090(a), HardFrame or Supra controller with DMA or, if you are working with programs that use DMA very much, use a NON DMA-Controller (like GVP, C Ltd <continued>