Archived from groups: alt.comp.hardware.pc-homebuilt (
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Juhan Leemet wrote:
> On Sun, 01 Aug 2004 23:14:39 -0500, David Maynard wrote:
>
>>John R Weiss wrote:
>>
>>>"David Maynard" <dNOTmayn@ev1.net> wrote...
>>>
>>>>Regardless of which calculation one thinks is the best estimate it's
>>>
>>>rather intuitive that two 550s, even summing to 1100, can't possibly be
>>>'twice as fast' as one 1200 of the same processor class unless
>>>something other than the processors is at play.
>>>
>>>That could well be true for a system running a single app.
>>
>>It's inherently true: 1100 can't possibly be bigger than 1200, much less
>>'twice' as big.
>>
>>
>>> However, once
>>>you get into multitasking, a dual-CPU system will be much more
>>>effective.
>>
>>The comment was about 'speed', which I presumed meant processing power.
>>'Effective' is another matter, depending on what you mean by it.
>>
>>
>>> I run database queries on my systems that hog an entire CPU for 15-60
>>>seconds at a stretch. On the single-CPU machine, all other processes
>>>stop cold.
>>
>>Well, they shouldn't 'stop cold' unless you've got priorities set to
>>allocate CPU time exclusively to the database app.
>
>
> Depends on the "O/S". I remember having that experience when running
> big/long Access97 queries on Windows98 at a client site. Access is nice.
> Windows98 blows chunks. That "cooperative multitasking" b.s. (dunno if
> they've finally got rid of it? no, I guess then it wouldn't "act like
> windows", would it?) was quite probably at fault. In my case, I had
> written some queries using VBA, so that I could do special programmed
> selections, and processing. Turned out that while the VBA loop was
> running, nothing else would get any CPU. I had to put in "breaks" into the
> code: e.g. count 100 iterations in the loop and make special system calls
> to "voluntarily give up" the CPU to anyone that might want it. I'm used to
> preemptive multi-tasking and time-slicing schedulers in "real" O/S, so
> this was really/specially annoying. To actually have to write in kludges
> to make multitasking work is an abomination! BTW, while I was kludging I
> put in some "progress indicators". They also helped, since the queries
> were slow/long and sometimes you wondered if it had crashed (again?).
Well, I had the impression he was using a Win2K/XP system. The Win9x series
is completely different.
>>> On the dual, I work merrily along while the DB ferments in the
>>> background.
>>
>>That is easily explained by postulating that the database app runs on
>>only one processor so there's half of the system left 'idle' for your
>>other apps to run in. That would be true regardless of what the combined
>>'speed' is and doesn't say anything about it.
>>
>>
>>>Also, it is difficult to compare 2 systems -- 1 single-CPU and 1
>>>dual-CPU -- that are otherwise totally equal. Maybe I'll dust off my
>>>old 550, pull out a CPU, and compare scores...
>>
>>I don't understand why you say the comparison of otherwise equal systems
>>is 'difficult'.
>
>
> Yeah. I generally favor multiprocessor systems for that reason. There are
> more CPUs to share the load, and there's more likely one "free" to handle
> any new work or event.
>
> BTW, you cannot always linearly generalize viz. clock rates, etc. I had a
> case where a quad-CPU system seemed to not perform much better (if at all)
> than a dual-CPU on the same mobo. The quad CPUs were actually higher clock
> rate (but different internal architecture, tho same instruction set), but
> smaller cache. I think it was a combination of cache starvation and
> perhaps also memory bus choking that limited performance.
Yes. That's why I said processors of the same class.
>
> p.s. These days I run Solaris and Linux and I'm much happier. YMMV
>