IMSAI News?

Back when Todd Fischer was starting the development of his Imsai-II I had reservations about his plan to use a Z80 scion rather than the "real-McCoy, and using an SMPSU that provided regulated supply rather than the traditional unregulated supplies. Whe he asked me to become involved in the development I had a full plate and couldn't do it, but I certainly didn't like the "smell" of the notion of trying to compete in the rabidly competitive PC market, which clearly what it looked like he was wanting to do. Hoping to capitalize on the availability of low-cost PSU hardware, that having been a major problem with the early S-100 hardware, and that being a major weight/shipping-cost contributor, I think he was seeing the Z800, or whatever it was, as a PC-competitive vehicle, which it wasn't. In fact, I don't believe Zilog has anything capable of competing in that market at all. If one wants a product that is both CP/M-80 capable and also able to run the on-card firmware of ISA card peripherals, the V-40/V50 from NEC, and some of their scions, though the later scions no longer have the 8080 core, which is a problem, offer an alternative. The V40/V50 contain the serial I/O, timers, DMAC's, interrupt hardware, etc, that readily support executing 8086-code, thereby making the use of ISA boards straightforward, at least as part of the CP/M BIOS. They also offer speed advanatages that can't be overlooked, but generating the S-100 timing from their signals is not trivial and requires the sacrifice of some performance. If one wants to "have is cake (in the form of the 8080-compatible hardware execution unit) and eat it too (in the form of the 8086 instruction set compatibility)," the V50 certain would be my choice. I've built up a board that appears to generate the required timing from a V50 to run a basic S-100 interface compatible with late-70's (pre-IEEE 696 standard) S-100 hardware. Since I don't have an Imsai or Altair front-panel, I have no way of ensuring that such a device would work with this board, and since I've not had the time or motivation to get it done, I've not worked out the details of swtiching back and forth between the 8080 execution unit and the 8086 execution unit, which would be required to make all this stuff work properly. One of these days ... Dick ----- Original Message ----- From: "Bob Shannon" <bshannon(a)tiac.net> To: <cctalk(a)classiccmp.org> Sent: Saturday, June 15, 2002 8:04 AM Subject: Re: IMSAI News?