On 2015-Nov-01, at 12:27 AM, rod wrote: > On 31/10/15 21:36, tony duell wrote: >>> Hi Tony >>> I seem to remember, certainly in OEM land there were dev. >>> systems with front panels and production systems without. >>> In other words the front panel was option and could be fitted. >> Sure. The PDP8/f and PDP8/m are the well-known example. Many of the >> Philips P800s had optional full panels too (fortunately the ones I own >> do have the full panels). And there must be many more >> >> But I still claim it is difficult to add a panel to a machine that was never >> designed to have one. In the case of machines with optional full >> frontpanels the machine was designed to take a frontpanel and either >> to also run without it or there was some minimal panel (boot/reset/not >> much else) that provided enough logic that the processor didn't realise >> it didn't have the full panel (if you see what I mean). >> >> -tony
> Yes much as I thought. What about S100 systems? > Many did have lamps and switches but I can think of a couple that didn't . > Northstar Horizon for one and Cromenco also. The other way round I think, the Altair and IMSAI were the only S100 machines I recall OTTOMH which had blinkenlight panels. The vast majority of them didn't. Northstar & Cromemco as you say, Compu-Pro, Vector-Graphic, Processor Tech SOL, Poly 88, etc. : no blinken. One problem with a front panel on an S100 machine - or any microprocessor-based machine - is getting access to the program counter so you can tell it to start running at some arbitrary address. The Altair/IMSAI panels resolved this with a hack, jamming a jump instruction into the processor data lines (not the S100 bus data lines) via a special connector to a special processor card. In general, even if you can bus master to put stuff into memory, front panel functionality is pretty limited if you don't have control ever execution.
