Benchmark Wars (was Re: gauging interest in VAX 6000-530)

From: Mike Cheponis <mac_at_Wireless.Com>
Date: Sun Oct 24 18:01:48 1999

> If you're doing ray tracing, get a fast PC.
> If you're timesharing dozens of people, a VAX is not a bad choice.

I remain unconvinced(!).

> It's all about "balance" and truly good designers can get good balance for
> the task at hand without being stuck in some rut.

That's certainly true, and nice ancedote w/HP2000 vs 11/55.

> --Chuck

> (For Mike, have you ever actually run a 486 based PC architecture machine
> with a dozen actual serial interfaces connected to terminals? It is
> instructive because the damn things saturate the ISA bus and no disk
> traffic happens at all!

(Hi Chuck!)

Here's my back-of-the-envelope:

The 16-bit ISA bus on a 486dx2/66 runs at 8 MHz. The total bus throughput
for memory operations is 32 megabits/sec. (4 cycles = 500 ns, 16 bits/cycle).

If your dozen uarts are on a memory-mapped card, and you're pumping 19.200
b/s continuously to the dozen uarts, that's 184,320 b/s required by the
uarts. That's only about 0.6% of the available bus bandwidth (about one
uart transfer every 174 Main Memory references.) Yes, you do have to work hard
with such slow memory, and now we understand why cache memory was so important
even on dx2/66 motherboards. So, yeah, keeping a dozen terminals blazing
output would be "fun" with an ISA-only bus!


(Incidentally, I am -not- advocating ISA as some sort of "wunderbus"; on the
 contrary, I remain amazed that it has taken the PC industry as long as it
 has to recognize the importance of I/O speed. 64-bit 66 MHz PCI and 2x AGP
 are steps in the right direction... Yes, the microcomputer industry seems
 hellbent on re-discovering what the mainframe and mini guys knew 20 or 40
 years ago...)

---------

Something happened between the days of the 1620 and 1401, and Today;
Back Then, Men were Men and programmers knew how to write code that was
fast, tiny, and worked great. Today, anything under 100 MB is considered
a "small" program... And performance? Ha! Don't make me laugh! Beat it
to death with Uncle Gordon Moore's 2x every 18 months, they say...

-Mike Cheponis
Received on Sun Oct 24 1999 - 18:01:48 BST