eric@snark.UUCP (Eric S. Raymond) (08/15/87)
Ny new personal micro is a Compaq-386 clone running at 16 Mhz. The memory
is 100-nsec static-column DRAMs, so it runs at something between 0 and 1
wait states. The box consequently goes like bat out of hell on those in-memory
straightaways, even compared to my 3B1 which (using a 10Mhz 68010) is no
slouch. A copy of Microport's 386 System V.3 with DOS bridge is on order for
it.
Now for the bad news. My mass storage devices are a pair of Seagate 251s
hanging off a Western Digital WA-2 ST506 controller, rated at (I think) 80
milliseconds average access time (someone please correct me if that's wrong).
My questions:
1) How can I tell if I've fallen into the minicomputer trap? -- that
is, how can I tell if my I/O bandwidth is low enough that I'll
mostly lose my processor speed advantage because I'm waiting on
disk transfers?
2) If (1) is a problem, is there some method that can give me a rough
idea of what kind of drive performance I should pay for to achieve
a given fraction of maximum theoretical performance for the
processor-memory combination?
3) I've read man pages for system activity profilers and I know how
to get down and dirty with the System V tunable parameter tables.
I don't yet have a good feel for how to hunt systematically for
performance/economy maxima in that parameter space. Comments and
war stories from unix.wizards with performance tuning savvy are
solicited.
I've cross-posted this to comp.arch because the situation has aroused my
curiosity about general methods for matching I/O subsystem and processor
performance -- is this still a black art?
For those of you looking for a good cheap expandable UNIX box:
The system cost me $2495; you can get one like it for no more than $2695.
That includes 1 meg of RAM, the Winchesters and an AT-format 1.2 meg, plus a
MCA/HGA CRT controller (with printer port), and choice of Phoenix or Award
AT-compatible BIOS, all sitting in an AT-sized case.
The box is manufactured by an outfit called Micronics, but they don't sell
Q1; I got mine from an outfit called Vesta Computers (phone: 1-(800)-843-5278).
The Vesta people and the Micronics tech I talked with were open, helpful and
a pleasure to deal with, and Vesta's prices are very aggressive and dropping
weekly. Tell them Eric sent you.
Now if only the processor weren't an Intel chip... ;-( ;-)
--
Eric S. Raymond
UUCP: {{seismo,ihnp4,rutgers}!cbmvax,sdcrdcf!burdvax,vu-vlsi}!snark!eric
Post: 22 South Warren Avenue, Malvern, PA 19355 Phone: (215)-296-5718steve@nuchat.UUCP (Steve Nuchia) (08/28/87)
In article <125@snark.UUCP>, eric@snark.UUCP (Eric S. Raymond) writes: > Ny new personal micro is a Compaq-386 clone running at 16 Mhz. The memory > > Now for the bad news. My mass storage devices are a pair of Seagate 251s > hanging off a Western Digital WA-2 ST506 controller, rated at (I think) 80 > milliseconds average access time (someone please correct me if that's wrong). The 251, which uses the same case components as the dreaded 225, has a new head positioning mechanism, which it shares with the 277. They are rated at something more like 40 ms. I have a 4096 and a 251 running, and they perform comparably. There is a bug in microport's driver that is causing an error at drive select changover about once a day, but other than that I'm happy with the drives. I'd rather have an eagle, but the prices aren't really comparable. :-) > Now if only the processor weren't an Intel chip... ;-( ;-) "you get what you pay for". sometimes. I bought an AT because I couldn't afford a real computer, I'll probably be upgrading to a 386 "soon". I may never get a real computer. A question of my own, for the original poster or anyone else with microport's 386 unix; response by mail is appropriate: I saw an add that indicated that the V/386 product supported "demand paged virtual memory". I this true, or have they come up with an obscure new meaning for those words? I didn't think the 386 had the hardware for real demand paging, am I wrong? Steve Nuchia {{soma,academ}!uhnix1,sun!housun}!nuchat!stevee