jbm@uncle.UUCP (John B. Milton) (10/24/88)
In article <733@bacchus.UUCP> darren@bacchus.UUCP (Darren Friedlein) writes: >OK - here's another question. What's involved in building a card cage for >the UNIXpc if it was possible to get these connectors? Could it be done >with like ribbon cable? Since this machine IS based on a back-plane, this >would appear to be possible. Any comments? It is not strictly a bus like S-100. 100 pins come off the mother board, and 99 pin Eurocard-ish connectors are used in the bus. Each slot has 3 pins for slot ID, which are of course different for each slot. Other than that, the rest of the signals (as far as I know) are bused. The little 3 slot bus board in the UNIXpc is an 8 layer board. There is an "Expansion Unit" out there, Comcode 405176785, I've seen a price of $1695 for it. It adds 5 slots and has a board that plugs into one of the slots. You can't put memory in it. I have thought about building a bigger bus. My thought was to take the little three slot bus out and use a new stacked 8 slot bus. Turn the whole mess into a vertical "tower" arrangement: +------ mother board v [==]| <-- floppy $$$$| <-- hard drive(s) $$$$| < ----| \ ----| | ----| | ----| |-- 8 slots ----| | ----| | ----| | ----| / %%%% <-- Power supply %%%% The problem is, who would buy it? A new bus PC would have to layed out. Probably even re-designed to be properly balance for all 8 slots. The power supply would have to be out-and-out changed. New cables: hard disk (3), floppy (2), video, keyboard. You would need some kind of base for the monitor. Few people would even look into it without a proper case, and on and on. How many people out there can afford 8 cards for this beastie anyway? The better idea seems to be a big project looming in the future. What everyone wants is lots of cheap expansion. Nothing for this machine is cheap compared to the PClones. You guessed it, why not build an IBM-PC bus bridge? A SCSI card for the PCs only costs $45. I think they're putting serial cards in Cracker Jack boxes these days. There are lots of other tantelizing boards out there: Hard and floppy disk, xGA, serial, parallel, IEEE-488, gaggles of co-processors. I don't even want to think about DMA just yet. The part that scares me most is noise trouble. My friend James Nugen (jcn@uncle) has had an IBM hard disk controller working on an Amiga, so this is close along those lines. The software for this idea would be a nightmare. The IBM-PC BIOS pieces parts are on cards, a lot of good that does us. I don't think it would be very fun to run an 8086 interpreter in the device driver. This all leads to the same problems the MINIX folks are having with all these boards. It also means we have a good source for drivers, hard disk in particular. I would envision a new twist to get this attached to the UNIXpc. A lot of people are already maxed out to 3 cards, so they don't have a slot to spare. For something like a bridge, which needs everything on the bus, I am wondering if a flexible PC edge connector tap might work. I thought this one up talking to Gary Sanders (gws@n8emr) on the phone. The idea is to design a flexible PC board which matches the fingers on the mother board. You detach the mother board from the bus connector, fold the flexible PC up the right way, wrap it around the mother board fingers, and then carefully plug the whole mess back into the bus edge connector. The flexible PC could be layed out with interleaved grounds and heavy traces for power. It could even be folded between the UNIXpc and a PC box for easier Advanced Cable Management. The problems would be cost and mechanical repeatability of the connector end. Has anyone ever seen this done before? Just thought I'd put one MORE iron in the fire. John -- John Bly Milton IV, jbm@uncle.UUCP, n8emr!uncle!jbm@osu-cis.cis.ohio-state.edu home (614) 294-4823, work (614) 764-4272; Send vi tricks, I'm making a manual