17 Apr
2005
17 Apr
'05
10 p.m.
snipe
Lyle wrote:
McNamara),
> I expected an 11/70 to be instruction for
instruction faster - but
> add all the cache and complexity - maybe the 55 with bipolar ~was~
faster?
How about
compared to a 11/70 with a PEP70 instead of factory memory and
cache?
Isn't a 55 just a 45 with bipolar instead of core? or was that a 50?
Read "Computer Engineering" (Gorden Bell, J. Craig Mudge, John E.
Copyright 1978 by Digital Equipment Corporation
Page 408
--------
Model Basic Instructions Floating Point
Inst. per second* Inst. per second
-------------------------------------------
11/70 36 671
11/55 41 725
* Relative to 11/03
No brainer - the 11/55 wins hands down.
sigh - I haven't memorized the DEC sacred texts yet;) no hardcopy, only
pdf...
So the 55 is roughly 14% faster than 70 - probably due to main memory
timing.
This might not be the case with the PEP70, though it's not stock.
Interesting
that the FP is only 8% faster - given that they are likely similarly
microded and
memory would not be such an issue working out of the FP registers. Clock
speed?
Then again... if one put 2 MW of 300ns ram on a 70.. well the 55 was only
18 bit address ;)
Anybody know the microclock frequency of both models? Variable timing/phase?
This variable microclock trick was later used in Vax/750 hot wiring kits..
On a similar vein, wasn't the 11/34c clock slowed to allow for cache timing,
making
it slower than a 34A? (for uncached accesses) Is is this a possible reason
for the 70's
poor performance? Running code withing the cache should have beaten the 55!
h