24 Oct
1999
24 Oct
'99
9:24 a.m.
Mark Green wrote:
Mike Cheponis wrote:
> Looks like the 6500 was about 13 VAX-11/780 MIPS. That would make it about
> 2x to 3x slower than a 486DX2/66.
Integer performance is a very misleading
measure of performance when you are talking about system performance.
My main belief is that nobody is going to keep a VAX anything running with
dozens of simultaneous users. So, if a VAX is to be something close
to "useful" today, it'll be in single-user mode. In that case, Integer
performance is very important.
Now, perhaps if we were to port Apache to the VAX, and used that I/O bandwidth
on multiple DS3s, well, that's great.
for example, all except
the most recent PCs, there is only a single bus. This bus
must be used for all memory transfers, graphics, I/O, etc.
On a single user system, this is sometimes okay, but for
multiple users forget it.
Hey, I'm not saying the original IBM PC was going to outperform the VAX 6500;
but a modern PC will crush any VAX in any application, IMHO, with equivalent
h/w attached.
Most of the VAXes had multiple
busses, and each was dedicated to a particular function.
What are:
1) The names of these busses?
2) Their uses?
3) Their peak and average throughputs?
I certainly know for a fact that UNIBUS performed very poorly. I don't have
data at my fingertips, but it seems to me it was around 10 Mb/s (that
megabits/sec) peak throughput. [I prefer measuring throughputs in bits/sec
since that normalizes across different bus widths.]
This meant that the combined throughput was
considerably more
than any existing PC bus.
I'm trying to get away from fuzzy terms like "considerably more" and get to
hard, cold numbers. Just -exactly- how fast were these things?
And, if you don't like Dhyrstone 2.1, then what benchmarks -can- we use?
One of the main problems with
all of the PC chips is the limited speed of the FSB. Its
no good having high integer performance if you can't get
the data in or out of the CPU.
Fast dual-port SRAM solves the problem, but commodity PCs aren't designed
that way. Also, the AGP bus uses mega-RAM to speed up PC graphics, for example.
I do a lot of high end graphics, both on PCs and SGIs.
of the SGI is at least 5x better than the best PC
configuration, and it can bury the PC on any app that moves a lot of data.
I appreciate the SGI vs PC datapoint, but what's the PC vs VAX datapoint?
Large systems were designed and built for throughput,
so its quite possible
that one of these old systems could outrun a modern PC in high throughput
applications.
OK, then what's the performance of a VAX running Apache vs a K7 running Apache?
-Mike Cheponis