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Well ... The "motherboard" of most S100 systems AFAIK were simply a a power supply and bunch of slots. Nothing onboard, your RAM fit in a slot, your CPU card
by tenebrisalietum 6y ago
Well ...
The "motherboard" of most S100 systems AFAIK were simply a a power supply and bunch of slots. Nothing onboard, your RAM fit in a slot, your CPU card fit in a slot, your video card or serial port for your terminal fit in a slot, your disk controller fit in a slot, etc.
The original IBM 5150 had RAM and CPU onboard, as well as a tape I/O port.
I did run into an old Zenith PC clone at a Goodwill a while back. I think dated from 1987.
Really weird system - the motherboard was an S100-style backplane that only had the Motorola MCxxx-whatever clock chip (a real one and even socketed). On a big ISA-style card was a 286 with a lot of other chips, another big ISA-style card that looked like RAM, and a third that had all the discrete components of your PC chipset - the PIT, the two UART chips, the two DMA controllers. I forget if the PICs were there or on the CPU board.
The BIOS was also weird ... had a built in monitor complete with assembler and disassembler commands.
Every single chip was socketed. It was ... bizarre. Had an MFM drive running DOS 2-point-something and an ISA VGA card in one of the slots. Still worked.
- jacquesm 6y agoIt's called a backplane.
- kevin_thibedeau 6y agoApple IIs had a (mostly) backplane architecture. It wasn't an uncommon thing.
- tyingq 6y agoVME bus 68xxx and 88xxx servers remained popular through the 90's as well.
- tyingq 6y agoSounds like the Z-286. The US Air Force bought lots of these. A diagram that shows the backplane: https://arvutimuuseum.ee/th99/m/U-Z/34130.htm https://arvutimuuseum.ee/th99/m/U-Z/34130.htm Sales brochure: https://www.1000bit.it/js/web/viewer.html?file=%2Fad%2Fbro%2Fzenith%2Fzenithpc%2Dz286col%2Epdf#zoom=page-fit https://www.1000bit.it/js/web/viewer.html?file=%2Fad%2Fbro%2...
- tenebrisalietum 6y agoYep, I think it was. I do remember the VGA card being plugged into that small slot at the top. I still have the "chipset" card because it's super interesting to have something to show that a PC chipset was actual physical chips at some point.
- tssva 6y agoPrior to the Z-286 line Zenith made a line of PC compatibles with an 8 slot 8-bit ISA backplane design, the Z-150 desktop and Z-160 transportable. The backplane board lacks the RTC and keyboard connection of the Z-286 backplane board and is therefore completely free of active components.
- bryanlarsen 6y agoNot all systems were like that, some were more like the 5150. Here's one: http://www.s100computers.com/Hardware%20Folder/HeathZenith/Motherboard/Motherboard.htm http://www.s100computers.com/Hardware%20Folder/HeathZenith/M...