I've actually looked at this before thinking it would be cool to have an expansion bus plug-in device that is basically a new processor on the system bus. Can't be done. The problem is that all the signals connecting to the system bus are buffered, meaning they are one-way traffic only. The address bus can only be driven by the 80C85 CPU and the data bus direction control is the same.
Ken On Tue, Jun 2, 2015 at 9:27 AM, Hiraghm <[email protected]> wrote: > Okay, so the system bus is used to connect to the DVI drive/video > expansion, but what are its total capabilities? > In an earlier message I wished for a cpu/ram upgrade for the M100. On > reading about the extRAM in Portable 100 issue November 1990 (page 17), I > began to wonder if one of you hardware types could build a very small > cpu/ram upgrade board that "takes over" for the CPU over the system bus. > > Maybe this is how QUAD adds the banks of RAM, I don't know. That's why I'm > asking, because I don't know. > > Not only would such a hardware upgrade speed up and expand the capability > of the M100 (would probably require a customized ROM via REX), but it would > make CP/M or even a custom FreeDOS (except FreeDOS is 32 bit :( ) possible. >
