[pups] Progress on 2.11BSD kernel
bqt at update.uu.se
Thu Mar 20 09:34:21 AEST 2003
On Wed, 19 Mar 2003, Steven M. Schultz wrote:
> The buffer cache must be entirely mapped by UMRs - so if you have a
> 32KB buffer the kernel will reserve 4 UMRs on a UNIBUS system.
> Realistically a 64KB buffer cache is about the maximum a UNIBUS system
> can have because that takes 8 of the UMRs.
Are the UMRs allocated and set up statically?
(I haven't looked inside 2BSD for a while now, and can't remember much of
the internals anymore.)
> With the old (thankfully no longer in use, etc) 3Com ethernet boards
> you had to disable 4 UMRs so the system could access the memory in the
> card - that made for a very tight fit.
How many UMRs does the system use? 8 for buffer cache, you might expect
one or two DH11s, that would require a few more, ethernet takes another
few, but it seems there shouldn't be such a shortage.
What did I miss?
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|| on a psychedelic trip
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