aps@decvax.UUCP (06/22/83)
In response to Greg Hill's comments/questions: First, we run our VAX-11/780 with the older MS780-C (16k chips) memory, interleaved. We have for about three years. Any VAX-11/780, with two memory controllers and an equal amount of memory per controller can. UNIX (as well as VMS) does not care though "throughput" may be a bit higher. The new memory for 780's from DEC, the MS780-E (MS780-F arrays) is supposed to be able to interleave with a single controller. I never looked into how this is done, though.
smk@linus.UUCP (Steven M. Kramer) (06/22/83)
This is an open question, but maybe aps@decvax can answer this:
What code is needed to perform the interleaving? Where is it
in UNIX? I believe Greg is going to buy the old memory, but we
would like to know how to get UNIX to do it? Or is this a wiring
option that is permanent? (which would be bad if 1 board died, since
we'd have to pull out a board in the other controller to keep the
memory count in each controller the same.) How much speed is gained
this way? Is it noticeable?
--
--steve kramer
{allegra,genrad,ihnp4,utzoo,philabs,uw-beaver}!linus!smk (UUCP)
linus!smk@mitre-bedford (ARPA)dmmartindale@watcgl.UUCP (Dave Martindale) (06/23/83)
From my understanding of how the memory is remapped when the Interleave Enable bit is turned on (it appears that sequential locations from each controller remain in order but alternate, like a perfect cut and shuffle of a card deck at the quadword level) I can't see how UNIX could survive turning on the interleave bit once it had already been loaded into non-interleaved memory. The bootloader could do it more easily - it could make a copy of itself that would reassemble properly when interleaving was turned on, and then very carefully enable interleaving and jump to the new code. The simplest, and ugliest way would be to simply have the *boo.cmd files on the floppy that boot the machine stuff the appropriate numbers into the memory controllers to set their base addresses and enable interleaving. Anyone out there with interleaved memory on a 780 who can tell us what you do? For 750's, can you even put multiple memory controllers on them? If so, are they able to do interleaving? Dave Martindale