Re: VAX9000 unearthed

[Paul Koning via cctalk]

> On Feb 18, 2022, at 4:30 PM, Chris Zach via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
>> XMI already existed as the system bus for the VAX 6000 series machines.    
>> I/O on the VAX 6000's was via an XMI-to-BI bridge.  I don't remember the 
>> exact performance specs on XMI, but it was wider and faster than BI.
> 
> I thought XMI was only supposed to be a CPU/memory bus, with IO being done by 
> multiple VaxBI busses. That's what we had on the 6000 at the computer 
> Society: 2 CPUs, memory, and two VaxBi with a SCSI disk controller on each.

From what was just reported, the 6000 series indeed did it that way.  But I 
think on the 9000 it was an I/O bus too.  I definitely remember some work on 
XMI based I/O devices, in particular an FDDI card.  And indeed you can find a 
spec for that device in http://www.bitsavers.org/pdf/dec/xmi/ .

        paul