Subject: RE: Minimal CP-M SBC design From: "Andrew Lynch" <lynchaj at yahoo.com> Date: Sat, 10 May 2008 14:43:26 -0400 To: <cctalk at classiccmp.org> It's not the ROM-ing of CP/M that disturbs me, but rather the "disklessness" of the thing. Wasn't the whole idea of CP/M originally to give you something to manage files on your floppy drives? I mean, that's what the bulk of the code in CP/M is for-- heaven knows, the support for other I/O is nothing to write home about. If one wants to enjoy a "vintage" experience, what sense is there in being diskless? At any rate, even something as simple as a WD1770- type controller added to the design would give that capability with a minimum of support "glue". Alternatively, one could stay diskless and add a sound-effects module to emulate the "chunk" and "grrr" of a head-load and seek--and the "thunk-click" of a drive door being opened and a floppy inserted. I still don't have the hang of this "vintage" thing yet, probably because I'm vintage myself. Please forgive my density... Cheers, Chuck -----REPLY----- Hi Chuck, I hear what you are saying and agree there is something just very disconcerting about diskless CP/M computers. However, CP/M in the CBIOS is really just about block devices and the OS really could care less whether you attach a 8" SSSD floppy, a CF drive or a ROM. It is all the same to the BDOS. My goal here is to *eventually* allow expansion to include IDE and floppy drives. As a matter of fact, the CBIOS does support IDE hard disks already but requires the interface IO card and the ECB backplane to attach it to the SBC. I have an IDE hard disk with CP/M format and some programs on it. My goal with the SBC using ROM/RAM drives was to allow something minimal to operate as a SBC and have some functionality with the option to expand to as desired. I am trying for a modular, low cost approach with easy to build increments. Assuming I get this SBC respun and into manufacturing my next project is to redo my ECB backplane as a PCB. After that will be the disk IO board and bus debuggers which are also made from prototype boards. My Test Prototype home brew computer was built entirely with prototype boards and point to point wiring. It supported IDE drives and even had a NEC765 FDC circuit built in. I wrote some software but never got around to test the FDC part since the machine started experiencing reliability problems which I think trace back to poor grounding and power distribution issues. The new PCB SBC version seems much more solid than the prototype did.

The SBC is something which works but gives only limited functionality. If that is enough, people can stop there. If they want more they can plug it into the ECB backplane and add peripheral cards. So far only two peripheral cards exist; the disk IO card and the bus debugger. Hopefully more in the future. I have some ideas kicking around in my head but am concentrating on the SBC for now. Thanks and have a nice weekend! Andrew Lynch