Double CPU on Win XP wronlgy seen on P5GD1

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Mirko

Hi all,

I'm having a problem with a P5GD1 pro mb, mounting a P5 3 Ghz.
The matter is that I verified a program that needs lot of CPU processing
actually runs slower than on a 1.5 Ghz system.

I've seen on th etask manager that the system never allows it to gather more
than 50% of cpu...

Inspecting Computer->Management->peripherals I found that my xp
configuration actually sees a TWIN processor but indeed the motherboard
doesn't carry any second CPU...

I think slower performance is obtained because of the 2-cpu setting .....

Anyone knows what the problem is and how to solve it ? Is it a BIOS known
problem ?
How can I set the system for single cpu ?

Thanks for any precious hint

Mirko
 
I'm having a problem with a P5GD1 pro mb, mounting a P5 3 Ghz.
Sorry it's a P4 3Ghz, not P5 ... of course.

Mirko
 
Mirko said:
Hi all,

I'm having a problem with a P5GD1 pro mb, mounting a P5 3 Ghz.
The matter is that I verified a program that needs lot of CPU processing
actually runs slower than on a 1.5 Ghz system.

I've seen on th etask manager that the system never allows it to gather
more than 50% of cpu...

Inspecting Computer->Management->peripherals I found that my xp
configuration actually sees a TWIN processor but indeed the motherboard
doesn't carry any second CPU...

I think slower performance is obtained because of the 2-cpu setting
.....

Anyone knows what the problem is and how to solve it ? Is it a BIOS
known problem ?
How can I set the system for single cpu ?

Thanks for any precious hint

Mirko
Click to expand...
Hyperthreading....
This is seen as multiple processors, and your configuration is correct. It
should not result in the program running this much slower, but there have
been plenty of reports of some systems running a little slower than you
would expect (perhaps 20%). There are some fairly important fixes in
latter XP updates to make this work 'right', and you should try these
before fiddleing. You should be able to disable HT in your BIOS, but you
will then have to do a repair install of XP to safely switch to the single
processor kernel. You can disable the MP support temporarily, by adding
the text '/ONECPU' to the boot.ini line for your setup, so you could try
this.
This is one area where AMD pointedly claim that the overhead of
hyperthreading, can make it work less well than a single threaded
processor of the same speed for many applications, but I have never heard
of it being quite as bad as for your system. Are you sure something else
isn't the cause of the speed difference (less RAM for example)?.

Best Wishes
 
Thanks Roger,

I've just read something about the hyperthreading technology, and surely
this is the reason for my slow perfoming app... RAM is at 512MB so surely
this is not a problem...

Just one question, I could'nt find an exact answer for... As you suggested I
should put /ONECPU on the boot.ini for testing, (I can't do this test right
now because I can't restart the machine, but I will soon try...)

Why do you say the setting in boot.ini is a 'temporarily' fix ? If this
solves my problem, is there any problem if I keep this setting instead of
reinstalling ?

(On MS site it doesn't give any contraindication)

Thanks again
 
Mirko said:
Thanks Roger,

I've just read something about the hyperthreading technology, and surely
this is the reason for my slow perfoming app... RAM is at 512MB so
surely
this is not a problem...

Just one question, I could'nt find an exact answer for... As you
suggested I
should put /ONECPU on the boot.ini for testing, (I can't do this test
right
now because I can't restart the machine, but I will soon try...)

Why do you say the setting in boot.ini is a 'temporarily' fix ? If this
solves my problem, is there any problem if I keep this setting instead
of
reinstalling ?

(On MS site it doesn't give any contraindication)

Thanks again
Click to expand...
You would need to disable hyperthreading in the BIOS, and then try
/ONECPU. With this done, though you will still be running the MP kernel,
you will only be running one 'virtual' CPU, and this will have access to
the full resources of the processor. /ONECPU, will stop XP from trying to
use the second 'virtual' hyperthreading part of the chip, but unless the
processor is switched to not use hyperthreading, it'll not have access to
the full performance. Using the MP kernel, has a small extra 'overhead'
when running in single processor mode.
How much RAM did the other system have?. Without knowing what the
application is, 512MB, could be very small indeed for some applications (I
have a database, and a graphic application, that both bottleneck on
memory, unless there is at least 2GB on the machine).

Best Wishes
 
Hi all,

I'm having a problem with a P5GD1 pro mb, mounting a P5 3 Ghz.
The matter is that I verified a program that needs lot of CPU processing
actually runs slower than on a 1.5 Ghz system.

I've seen on th etask manager that the system never allows it to gather more
than 50% of cpu...

Inspecting Computer->Management->peripherals I found that my xp
configuration actually sees a TWIN processor but indeed the motherboard
doesn't carry any second CPU...

I think slower performance is obtained because of the 2-cpu setting .....

Anyone knows what the problem is and how to solve it ? Is it a BIOS known
problem ?
How can I set the system for single cpu ?

Thanks for any precious hint

Mirko
Click to expand...

As Roger has pointed out, Hyperthreading explains why the performance
monitor is counting the performance of both virtual processors in
its count. When a single task runs flat out, it will be getting
50% of the machine's total performance. Starting a second task
(multitasking) allows the other 50% to be harvested from the
second virtual CPU.

Hyperthreading of two tasks, can be more demanding of the cache
and memory subsystem, and that is why not all combinations of
tasks benefit from hyperthreading.

I think some of the things you should consider -

1) The Prescott has a longer pipeline - I think it is 30 stages
compared to the Northwood's 20 stages. If a program has a lot
of branches that defy prediction, many times the contents of
the pipeline must be thrown away. The larger cache on the
processor compensates for that (i.e. the larger cache is not
just a 2X bonus, compared to a processor with 512KB cache - the
cache is larger for a reason).

2) Recent Intel processors have "thermal throttling". When the
CPU die temperature sensor hits 70C, the processing rate is
reduced, by computing not happening on all clock cycles.
You need to check whether you have adequate cooling to keep
the processor from reaching that temperature. For some
people, they use a larger after-market heatsink/fan to
solve the cooling problem. Your computer could probably
benefit from at least two computer case fans - one intake
fan on the front of the computer case, and one exhaust
fan on the back. This is necessary to keep the case air
temperature down, which makes the job of the CPU cooler
that much easier.

In the BIOS, under Advanced:CPU_Configuration, there is a
setting "Hyper Threading Technology" and you can [disable]
it if you want. By using that setting, no change will be
needed at the OS level, if you are experimenting.

HTH,
Paul
 
Thanks for clarification,

the other system has 512 Mb also but it's a non-hyperthreading Pentium M
(it's a Dell notebook).
The application is a custom ocr forms recognition system written in C, that
uses intensive CPU while performing module recognitions.

I read that some Manufacturers (one of them is just Dell) leave the
Hyperthreading default INACTIVE on their P4 systems, because of lower
performance on most single tasking programs actually used. I read that most
of the tests performed don't show enough enhancements to justify
hyperthreading active...

Mirko
 
Thanks for clarification,

the other system has 512 Mb also but it's a non-hyperthreading Pentium M
(it's a Dell notebook).
The application is a custom ocr forms recognition system written in C, that
uses intensive CPU while performing module recognitions.

I read that some Manufacturers (one of them is just Dell) leave the
Hyperthreading default INACTIVE on their P4 systems, because of lower
performance on most single tasking programs actually used. I read that most
of the tests performed don't show enough enhancements to justify
hyperthreading active...

Mirko
Click to expand...

Pentium-M has a different IPC than P4. You cannot compare clock rates
directly, as these benchmarks show.

http://www.anandtech.com/mobile/showdoc.aspx?i=1800&p=13

The fun begins when Pentium M is overclocked. Pentium M is great
for 3D graphics/gaming, but sucks at some other tasks.

http://www.tomshardware.com/cpu/20050525/pentium4-08.html

When behchmarking, it is possible some different compiler
flags are required to compensate for what the platforms do
best. There is a discussion here from 2003, so perhaps compilers
do a better job now. If there are C-flags specifically for
Pentium M you might get even better results for it.

http://forums.gentoo.org/viewtopic.php?t=77334

Paul
 
Your Pentium processor has HyperThreading, a feature of Intel's that allows
your CPU to process two threads at one time. Thus your computer CORRECTLY
sees the CPU as two processors. If you want to run it without the
HyperThreading turned On, go into your BIOS and turn it Off. Then it will
show up as one CPU.
 
The only applications* I have come across that are affected negatively by HT
are those server class apps that have been optimised for performance knowing
the architecture of the CPU's likely (sometimes separate code paths for
Intel and AMD chips for example). The s/w is sometimes manually optimised
down to the assembler level, but more usually at the C / C++ level to
achieve maximum throughput for a given CPU type and minimum cache size.

Intel has been quite pushy on getting programmers to write HT friendly code
so that the 2nd HT "cpu" can be doing more work to remedy this and gain HT a
place...

Those apps that do not benefit have AFAIK only small drops (<5%) in
performance on HT systems - not big at all. I have never noticed it or been
bothered by it.

I'd follow Paul's hint about CPU temp first. Check it in the BIOS. Try
taking the side off the computer and see if it drops & performance improves.

As Roger indicates, if you are going to change the CPU settings in the
BIOS - to HT Off- then use a Repair install to fix it up permanently - see
www.michaelstevenstech.com for Repair instructions.

- Tim

*MS Virtual PC, Virtual Server, SQL Server.

OT: PS Dave: are you feeling crook?
 
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