Is n´t it rediculous? 1 cpu faster than 2 cpus?
5 May 2006 6:39:24 UTC
Topic 191181
(moderation:
Can you all help me with this?
I have a GenuineIntel Intel(R) Pentium(R) 4 CPU 2.60GHz with Microsoft Windows XP Professional Edition, Service Pack 2, (05.01.2600.00) with 2 cpus.
I have installed the "revised" s41.06 albert file on my computer. The puzzling thing is that when I use the 2 cpus the crunching time is 2.5 hours for each wu (an average 1.25 hours per wu), while when i use only 1 cpu (set in the general preferences) the average crunching time is 1 hour. That is (if my maths are correct) 20% faster with one cpu.
Is n´t that strange?
Can I use some other preferences to get faster times with the use of the 2 cpus?
Waiting for your answers!
Gravity increases significantly in Autumn, because apples fall in large numbers during that time!
Is n´t it rediculous? 1 cpu faster than 2 cpus?
)
My guess is its in the HT.
You don't say if yout chip is single core HT or dual core, Difference being the HT core is only a logical one.
So it you disable HT then physical core runs quicker. About 80% quicker from memory.
Hope this helps
Thank you for your answer. I
)
Thank you for your answer. I am not 100% sure about it but i think that it is HT and not dual core! If this is the case, how can I disable the HT, and will it affect any other programs I use on my computer?
Can anybody else help?
P.S. It is amazing that a scientific program can link different people around the world in a common NOBLE cause!!!!
Gravity increases significantly in Autumn, because apples fall in large numbers during that time!
RE: Thank you for your
)
Generally you set that in the BIOS screens on boot up. Exactly where or how is motherboard dependent.
Roughly paraphrasing mine ( a GigaByte board running a P4 3GHz HT ):
- press 'del' ( or whatever ) during early boot up to enter BIOS setup
- find the screen which refers to this function, probably 'Advanced.....'
- ArrowUp/ArrowDown keys to select 'Hyperthreading...'
- use PageUp/PageDown keys to toggle that setting to 'off' or 'disable' or whatever..
- exit the BIOS setup via 'exit & save'
It is terrific, isn't it? ..... :-)
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Thank you, Mike! But can
)
Thank you, Mike!
But can somebody else answer the question if disabling HT will affect an y other software that I use?
Waiting patiently for an answer!
Thank you all again!
Gravity increases significantly in Autumn, because apples fall in large numbers during that time!
RE: Thank you, Mike! But
)
I'm allmost 100% sure that the answer to this os NO
RE: RE: Thank you for
)
Correct Mike, thats the way to do it in the bios.
I have though read many articles about this since Wednesday on the web, and many off these articles warns, that XP might NOT boot up afterwards, but you have to go back and enable HT again, in order to get XP up and running.
It's definately the HT.
)
It's definately the HT. Einstien doesn't fit entirely i nthe L1 cache, having two copies running at once greatly increases the number of cache misses slowing things down. At teh same time, akos's science apps achieve very near 100% cpu utilization, so you don't have a meaningful gain there.
RE: Correct Mike, thats the
)
Interesting I never knew that! I've just experimented by restarting, turning HT off in BIOS, rebooting fine, then restarting again to re-enable HT. No real worries, but noticeably slower on the non-HT boot. Hmmmm...
Specs:
Intel P4 3.0GHz HT
1.0G RAM
Win XP Pro SP2 plus latest updates
GigaByte 81915P Pro F6 ( ie. Intel 915P chipset )
Award BIOS ( i915P-6A79VG04C-00 )
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
If your PC is only crunching
)
If your PC is only crunching for on Einstein, why disable HyperThreading?
You can also set one of your "locations" on your accountpage to "On multiprocessors, use at most" "1" processor and then "move" the PC to that location using the "Computer summary" page for that PC.
This way you can still benefit from HyperThreading for all your other activities, while Einstein only runs one result at a time, getting access to all unused CPU-resources instead of sharing them between two results (and getting the full CPU-resources when the system is otherwise idle).
[EDIT]
the "On multiprocessors, use at most" trick also works on hyperthreaded Xeon DP/MP systems using the Trux calibrating BOINC client (or another client that allows for cpu-affinity), just divide the number of logical CPU's in the system by 2 and set that number as max.
for dual-core systems it should not be necessary to do this as these cpu's are 2 physical cpu's, as opposed to hyperthreaded cpu's where the resources of 1 physical cpu are spread over 2 logical cpu's.
[/EDIT]
RE: Can you all help me
)
You are looking at this wrong. You are doing 2 WUs in 1.25 time, because you are doing 2 simutaneously. When you are doing 1 at at time, it takes 2 hours to do two WUs. Yes there is a loss for the HT, because it is a logical processor, but it is a gain. Part of the reason of the slow down is the competition for the L2 Cache, but it still is faster to do the work with it on.