XMI goodies?

[Ian Viemeister]

On Fri, 9 Mar 2007, Ethan Dicks wrote:
> If I remember correctly, one may stuff up to 6 CPUs on the XMI bus,
> which is limited to a smallish number of total slots), but if one wants
> to max out the memory and have other peripherals in there, it might not
> be possible to have all 6 CPUs loaded.

Close...  The bus you're describing there is the LSB bus, which can handle
up to 8 CPU or memory modules (1-6 CPUs, VAX or Alpha; 1-7 memory modules,
up to 3.5GB on VAX), and one dedicated slot for the IO module.

The IO module connects to 1-4 XMI card cages which handle Ethernet, DSSI
(VAX only), SCSI (Alpha only), CI, and a bridge to VAXBI.

> Interesting stuff, if you want to run a VAX the size of a
> refrigerator.  The last one I saw in the wild was a few years ago, but
> there are quite a few in hobbyist hands.  Someone (here?) has
> described how to run one off of either single-phase or US 220VAC, but
> they shipped from DEC with 3-phase power, IIRC.

Well, they ship with a 3-phase input, but each of the three power
regulators is a simple single-phase load.  If the machine isn't loaded
with extra cards and storage PIUs, it can be run from a single regulator.

--Ian