MIT provides MULTICS source and documentation (DPS-8 simulation)

Roy J. Tellason rtellason at verizon.net
Wed Nov 14 22:36:47 CST 2007


On Tuesday 13 November 2007 22:17, dwight elvey wrote:
> > From: rtellason at verizon.net> > This is where I get a little puzzled
> > sometimes. Like that BB2 I mentioned, > that uses DMA to send a string of
> > bytes to the disk controller chip rather > than using the processor to do
> > those transfers. Why is not immediately > apparent to me since the
> > processor isn't doing anything else at that point > anyhow...>

Why does your quoting not handle line breaks well?

> Hi
>  I once wrote code to take avantage of DMA to disk. I was doing a search
> that required a case insensitive search. I found that on the processor
> I was running, it took almost as much time to read a track as it
> did to search the data on the track. I'd only have to wait, doing
> nothing on the first read. After that, I would just have to wait a
> little while until the next track was read, because I'd started
> the second DMA before I started searching the first buffer.

That makes sense.

>  In a multi user system, one could be handling all kinds of
> activities while the buffer was being loaded.

Multi-user in an 8-bit context doesn't sound real terrific to me,  for some 
reason,  though I don't see a problem with multiprocessing if it's done 
right.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin




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