On Dec 15, 22:42, Jerome H. Fine wrote:
> >Pete Turnbull wrote:
>
> > Yes, because that's about the only useful distinction -- the speed
> > increase brought by PMI memory is more than the clock difference
> > between 15MHz and 18MHz -- and of course if placed after the CPU,
even
> > a PMI-capable memory board operates as normal Q-Bus memory.
>
> Approximate speed increase from M8190-AB (KDJ11-BB)
> with normal DEC memory (obviously below the CPU) vs
> M8190-AE (KDJ11-BF) with DEC PMI memory above
> the CPU was about 33%. An assembly which took about
> 4.5 minutes was reduced to about 3 minutes. I can't recall
> the exact numbers or exactly what I tried, but the test with
> the M8190-AB and the PMI memory above the CPU took
> about 23% less time than 4.5 minutes. I then tried the
> M8190-AE and normal DEC memory below the CPU
> and that took about 10% less time than 4.5 minutes. When
> the PMI memory was below the M8190-AE, that also
> took about 10% less than the 4.5 minutes.
So, taking the M8190-AB as baseline, and doing some arithmetic:
M8190-AB M8190-AE
15MHz 18MHz
non-PMI 1.0 1.1
PMI memory 1.3 1.5
18MHz is 1.2 times 15MHz, so it seems other operations on the bus
are reducing the effect of the clock speed increase. Of course, that
might also be due to using memory with a different cycle time. Still,
it's clear that the PMI makes a bigger difference than the clock speed,
going from 15MHz to 18MHz.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Tue Dec 16 2003 - 12:16:04 GMT