[HECnet] PDXVAX - 40MB Memory - VAXstation 4000/VLC?

[John Wilson]

From: Johnny Billquist <bqt at softjar.se>

Modifying RSX to use the TSTSET instead of ASRB for spin locks would be 
easy. It's just a macro in the sources. Not sure what WRTLCK would be 
used for, though. But it's been a while since I looked at these 
instructions, so I don't remember the details of them.

Yeah I know what you mean, how is a write not already interlocked?   So I
figure what they're getting at is, TSTSET and WRTLCK are interlocked with
regard to *each other*.   Well that would work anyway ... now I'm trying
to picture which is easier to design, a multi-port Q-bus memory, or some
kind of shim which isolates a CPU card and negotiates bus masterhood on
its behalf instead of assuming the CPU card is The Decider.   I'm trying to
picture where per-CPU peripherals go in that case so the I/O page is still
private but DMA isn't ... ow my head!

John Wilson
D Bit