CompuServe Messages

The older revisions of the A500 (rev. 5) used the 256×1 bit chips which required 16 chips to get 512K. The newer rev. 6 A500's use 256×4 bit chips which requires only four chips for 512K. Another 512K could be added to the motherboard, BUT doing so would prevent you from installing an A501-expander. (This includes some if not all expanders that use the A501 slot.) The way the memory is "hardwired" allows for one or the other. I've heard of hacks that allow both, but haven't seen them. The normal way to increase "graphics memory" (what CHIP memory is called under AmigaDOS 2.04), is to plug an A501 or "clone" into the A501 slot and cut a trace that normally maps the memory into "$c0-". With the trace cut (jumper JP-7) the A501 would be 512K of CHIP memory. Other expanders such as the BASEBoard, and the AdRAM540 can be configured with part of its memory CHIP, and the rest either FAST or "$c0-". Also, you will need the ECS Agnus (#8372a). IF you have it you will need to "flip" the JP-2 jumper. This jumper is three small silver pads, the middle & bottom pads are connected for 512K of CHIP. The top & middle pads are connected for 1024K of CHIP. Only two of the pads can be connected, you will have to disconnect the trace if you solder the other pad. The JP-2 jumper affects ONLY the Agnus to alert it to what mode to run in. Ron.