CompuServe Messages

Charlie, The Zorro-II bus specifications reserve 8 megs of memory space for autoconfiguration by the addon peripherals. DMA is limited to this 8 megs, as is the addressing capability of the CPU on the motherboard. With an add-on CPU on the expansion accellerator board taking over the process, it can address additional memory contained on it's board, but other peripherals in the system cannot (i.e., it cannot be accessed by the DMA controller on the motherboard, and therefore cannot be accessed by any other boards in the system). Some third-party CPU boards do allow for memory to be added beyond the reserved autoconfig address space. The standard 2630 does not – it's 4 megs of memory configure into the standard autoconfig space. The advantage to this is that a DMA harddisk controller can read into/write from this 32-bit memory directly via DMA access. The dis-advantage is that this only leaves 4 additional megs of "autoconfig" memory available to the other boards in the system. Hope this helps…. – BobR