VMEbus Systems? Crates? Where to Start?

[segaloco]

Time to time I see VME single-board systems, especially 68000, pop up and want to snag one, but I know next to nothing about the system architecture in practice. As I understand it there is a backplane or "crate" and then the VME modules are slotted in, but how does the bus arbitration actually work? Happy to be directed towards literature but also just curious of peoples' experiences with building and using VME systems. What does a minimum viable system look like?

 

[Al Kossow]

A lot of vme people hang out on the vme channel on the cctlk discord

Bus arbitration started out as a separate board on early vme systems, but moved onto the cpu board later

You can build a system with later motorola mvme cards, but those often bring out things like scsi serial and ethernet out the back
through the p2 connector and need matching i/o paddle cards which can be hard to find

There is a lot of VME documentation on bitsavers under http://bitsavers.org/pdf/motorola/VME

 

[djg]

Viable is based on what you do. "VME" was used with single card where its an excessively complicated power connector to crate of 21 boards. I think it was used mostly for embedded/industrial applications though SUN used it in there early computers. My work first used Multibus I then made the correct decision to skip Multibus II and moved to VME. Typical system was a processor card with some number of cards specific to the application. Some configurations we had the application in EPROM or equivalent on the processor and others we would have disk and boot an operating system. Sometimes we would have multiple processor cards. Suspect if your playing you want a disk and OS. Serial communciations was common and many were hidden behing application specific intefaces which could be buttons and indicators. Early processor cards needed separate disk controller. Later cards had complete system with processor, memory, serial, video, disk interface etc on single card.

High level discussion of arbitration from web search.
https://www.vita.com/VMEbus-Arbitration