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CPU for multitasking - Page 2

post #21 of 34
1/31/05 at 2:10am
Quote:
Originally Posted by ChaosBlizzard
For that kind of money you can build a great dual Xeon system. I spent $3300.00+ on my dual P3 system. It has other things, like RAID and what not though.

Or he can wait until dual core CPUs come out.
For that kind of money, it's conceivable to build a dual opteron system with dual SLI graphics; or conceivably even a quad Xeon/Opteron system; simply put, not worth it. I believe the LT I was mentioning was originally designed for the military.
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post #22 of 34
2/1/05 at 12:57am
Quote:
Originally Posted by ChaosBlizzard
If it's using 100% of its processing power the cache is full. You tell me otherwise and you need to go back to the books.

Runway thread and pre-emptive don't belong in the same sentence with each other. When was the last time you seen a "run-away" thread in a pre-emptive system? Besides, today’s systems use 2, 3 or sometimes even more ways to schedule a thread and run a process.

You do realize Windows 2000 is both a co-operative system, pre-emptive system, and a priority scheduling system?
I should hit the books? You're the one making outrageous claims.

Are you saying that if I write a simple two-instruction program, a NOOP and a jump to that noop (Which would take the CPU to a hundred percent), that it would use up the entire L1 and L2 cache, both instruction and data? That makes absolutely no sense.

I guess you're going to also tell me where everywhere it's been mentioned that having more cache on a processor helps it keep it's pipeline full, despite the fact that it's at 100% usage either way, that those people were either lying or incorrect? Perhaps you should go tell Anand to "hit the books".
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post #23 of 34
2/10/05 at 2:48am
Thread Starter 
Well, the results of my little experiment are in and are a little surprising. I didn't get the 2.0 Dothan, so I put a 1.7 Dothan (Sony A190) up against a 3.06 Pentium with Hyperthreading (Spny GRT360ZG).

To test them, first I ran PCMark04 solo as a control. Then I used iTunes to batch convert a number of AAC files to MP3.

Run solo, the Dothan scored 3431 on PCMark04, while the P4 scored 3965. The Dothan converted the files at around 15x, the P4 at around 21x.

Then I tried my multitasking test. iTunes uses virtually 100% processor load when converting, so I had the conversion running in the background, and then ran PCMark04 over the top.

And that's when it got interesting. The 1.7 Dothan scored 1900 on PCMark04, or 55% of the solo score. The 3.06 Pentium 4 could only manage 1765, or around 44% of the solo score.

So on the face of it, the Dothan handles this multitasking exercise better.

Any thoughts?

Steve
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post #24 of 34
2/10/05 at 3:06am
It could be because the iTunes was treated as a background application, which meant that it was almost ignored by the single-threaded processor while it was treated as a loyal old friend by the multi-threaded one. It could also have something to do with Windows not being good at handling multi-processor configs.

Or it could just be that the Hyperthreading on Pentium 4s is lousy and not really worth as much as people always thought, though that's a claim I'm very hesitant to make.
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post #25 of 34
2/10/05 at 3:22am
Thread Starter 
I just checked the conversion rates of the two CPUs in another run through. It's hard to be defintitive because it goes up and down, but the P4 dropped to about 15-17 and the Dothan dropped to around 13.

I did read somewhere that the Dothan was very good at converting to LAME MP3, but then it should have done better in the solo tests.

So I'm a little mystified the p4 didn't do better. Maybe the 3.06 is an earlier tyoe of multithreading, or my setup wasn't the best test of it.

Cheers

Steve
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post #26 of 34
2/10/05 at 11:29am
Did you make sure hyperthreaing was turned on on the P4? In the task manager did it show up as two CPUs?
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post #27 of 34
2/10/05 at 1:26pm
Thread Starter 
Hyperthreading is enabled in the BIOS, but in Task Manager only one CPU is shown.

Steve
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post #28 of 34
2/10/05 at 1:47pm
Make sure you have individual TaskMgr charts for each virtual processor. Open Task Manager, go to View --> CPU History --> One Graph Per CPU.
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post #29 of 34
2/10/05 at 2:12pm
Thread Starter 
OK, have that. That was my original settings.

Cheers
Steve
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post #30 of 34
3/1/05 at 11:57am
Thread Starter 
Just for the hell of it I revisted my little test. This time I ran a virus scan with Norton AV, a spyware scan with Microsoft antispyware and PCMark04.

Blow me down if the Dothan didn't still bench better than the P4.

Go figure.

I also must get a life.

Steve
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post #31 of 34
3/1/05 at 12:34pm
switch to a mac
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post #32 of 34
3/1/05 at 1:16pm

Pipelines

The P4 is a terrible multitasking cpu. Its deep pipelines mean that every context switch flushes a lot of instructions. Every disk IO, network IO, and input IO generates an IRQ and potentially a pipeline flush. Hyperthreading is a way to fool the OS into thinking it can dispatch threads and IRQs differently (SMP v uniproc mode) to help mitigate this issue and keep the pipelines full.

(IRQ's are killer for x86 performance. IBM for example, recommends having the equivilent of one 1 GHz P3 for each gigabit NIC just to handle the IRQ load generated by the NIC when sizing servers.)

What I do is offload my encoding to a P4 desktop. Any file in the videoin dir gets picked up by a script, encoded and put into videoout dir. I pick the file up over the network or play it directly from the P4 via a network share. Zero cpu utilization on my laptop except for the network traffic.

If you keep up with what's happening with the IBM Cell Processors, it looks like its designed to solve this problem. Its basically a server cluster on a chip.
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post #33 of 34
3/1/05 at 2:42pm
Quote:
Originally Posted by HardBall
the A64 3700 will definitely do the best, not because of the CPU core alone, but more because of the Hypertransport at 1600MHz duplex, and the lower memory latency by the on die controllers, which are both important in multitasking. And 3700 will be about 15-20% faster than a 2.0 GHz Dothan, but neither in honesty, will blow anyone away in multitasking. If you are a serious multitasker, the best thing is not to get an LT, but to get a dual Xeon or Opteron to supplement the abilities of your LT.

Well I ordered the 4750 with then 3700 so I am hoping that it can handle multi-tasking. Because my dulie anthalon desktop let's me multi-task up the wazoo.
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post #34 of 34
3/1/05 at 3:18pm
DUAL CORE! Available in year 2010!
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