On 2/18/22 15:35, Paul Koning wrote:
On Feb 18, 2022, at 3:18 PM, Gary Grebus <g...@grebus.com> wrote:
On 2/18/22 09:46, Paul Koning wrote:
...The 9000 also had its own I/O bus, XMI, different from BI. I don't know how
its performance compares, whether it was worth the effort.
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.
XMI was then also used as one of the possible I/O buses on the VAX 10000 and
AlphaServer 7000 and 8000 series machines, via a system bus to XMI bridge. So
the XMI I/O adapters were common across all these series of machines.
I didn't remember all those details, thanks.
There also was an effort at one point to adopt FutureBus in DEC systems. We
did a pile of design in the network architecture group to figure out how to
handle interrupts and bus cycles efficiently; I don't remember if anything
actually shipped with that stuff.
There was a FutureBus I/O subsystem for the AlphaServer 8000 series. It
was a qualified, orderable option, but I can't imagine we sold very many
(if any). It was done supposedly because the US Navy was standardizing
on FutureBus for some application. I vaguely recall DEC made an
Ethernet adapter that went on FutureBus, but you would have needed
another I/O bus to have a usable system.
The native I/O interface on the AlphaServer 8000 (aka TurboLaser) was
one or more system bus to "hose" modules, where a "hose" was a pair of
cables that provided a 32 bit data path in each direction. The hose
connected to a bridge module on the target I/O bus. There was support
for XMI, PCI, and FutureBus.
-- Gary
