[Unix-jun72] Why is V1 so slow?
wkt at tuhs.org
Mon May 5 07:36:32 EDT 2008
On Mon, May 05, 2008 at 07:10:11PM +1000, Peter Jeremy wrote:
> On Mon, May 05, 2008 at 02:52:29PM +1000, Warren Toomey wrote:
> > i= *c & 0277;
> ^^^^ 0377 maybe
> >But it's very sloooow. I wonder why; V7 on simh is much faster than V1.
> Is V1 executing more instructions to get the same thing done or is simh
> managing to execute V7 instruction streams (or maybe emulate higher-end
> PDP-11's) better? Judging by some of the earlier hardware comments,
> maybe V1 is thrashing.
I think there are output delays in the kernel, probably to deal with
the speed of mechanical output devices. When I use the compiler, the
compilations are fast, but doing an ls -l /bin takes ages. We might be
able to tweak out the delays.
For example, grep delay build/u9.s, and these lines in u4.s:
cmp r1,$11 / char = ht
movb $15.,toutt+0 / set time out to 15 clock tics
cmp r1,$15 / char = cr
movb $15.,toutt+0 / set time out to 15 clock ticks
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