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2.8Ghz 400Mhz versus 3.06Ghz 533Mhz Northwood

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May 6, 2006 4:35:32 AM

Could someone tell me if I would see much of a peformance difference by upgrading from the 2.8/400 to the 3.06/533? I believe the 3.06/533 has HT. I have the mobo for the 533 so I can swap it out of the 400 mobo and all I would need would be the chip. I realize it is only a 7% performance gain but I don't know if is actually more given the larger bus and HT.

Thank you.
May 6, 2006 6:03:21 AM

Depends on what chipset you are running, what sort of RAM you have, and how that RAM is setup.

eg: Dual-Channel PC2700 on a 533 MHz FSB (133 MHz QDR), eg: SiS 655 chipset, would be OK.

Also depends if you use any applications that take advantage of HyperThreading, or if you multitask heaps.
May 6, 2006 6:09:23 AM

By 2.8/400, you mean a northwood A chip. You sill see a total performance closer to 25%.
The early P4s were extremely bandwidth limited. Even with a 200/800 bus, the P4C did not have all the bandwidth it could use. Mosing from a 100/400 fbs to a 133/533 fsb will give more return than HT.
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May 6, 2006 6:14:43 AM

If his board lacks a dual-channel supporting chipset, then having a 533 MHz FSB, with SDRAM (PC133) or DDR-SDRAM (PC2700 - PC3200) isn't going to increase throughput to/from memory at all.
May 6, 2006 6:26:12 AM

The fsb, in single channel is 64 bits wide. At 400 mhz, that yields a (400 * 64) 25600 Mb/sec bus. A 533 bus on the other hand, would yield (533 * 64) 34112 Mb/sec. I think that would make a 533 fsb faster.
May 6, 2006 6:34:18 AM

CPU = 32 GB/sec+

FSB = 533.33 MHz x 64 bits / 8 (for byes) = 4266 MB/sec

Single-Channel RAM = 400 MHz x 64 bit / 8 (for bytes) = 3200 MB/sec
Dual-Channel RAM = 400 MHz x 128 bit /8 (for bytes) = 6400 MB/sec

The CPU is going via the FSB to RAM, and if the RAM is unable to feed the FSB, then it chokes the system.

You can have a 800 MHz x 64 bit FSB (6.4 GB/sec) connected to 200 MHz (DDR, single channel / 64 bit wide) RAM offering only 1.6 GB/sec.... you can, but it is totally pointless.
May 6, 2006 1:17:01 PM

Thank you all for your replies. I should have given you more information. I'm currently running a 850 chipset and the one I am proposing to install is a 850E chipset. My RAM is RDRAM PC800. Both mobos are available for the Dell 8200.

Can I assume the 850E chipset would have a board that supports dual channel?

Does this help in making a determination of the performance increase? Is it indeed closer to a 25% gain.
May 6, 2006 3:07:26 PM

The Intel i850 chipset is dual-channel RDRAM, and is likely to benefit from 533 MHz FSB (as the RAM can keep up).

The performance boost would only be 10% - 15% depending what you're doing with it though. In memory throughput starved applications performance will rise heaps, in applications that take advantage of HyperThreading you'll also see a large gain (eg: video encoding).
May 6, 2006 3:20:04 PM

You will see no benefit from the higher FSB in your case, just from the CPU clock.
The 800MHz RAMBUS is 16bit, but double pumped works as 32bit 400MHz. It runs on 2 channels, therefore providing 2x16x800/8=3200MB/s.
In both cases the bandwidth of the RAM will remain almost same considering that both mainboards have the i850 chispet. If you got other chipset, than the RAM type on the mainboard might be different(DDR or DDR2).
May 6, 2006 3:49:48 PM

Thanks guys.

So just so I'm clear, is there a discrepancy between gOJDO and TabrisDarkPeace in so far as the benefit or non-benefit of the higher FSB?

I think 15% would be a reasonable gain but if the only benefit is the higher clock speed i.e. ~7% then I doubt it would be worth it.

Both boards will only take RDRAM so I can't change the memory.

I believe I fit that catagory of having a memory starved application in that it can use upwards 4G of RAM. It also requires a ton of math to be executed simulaneously so I guess it would help to have HT?
May 7, 2006 5:13:27 AM

If that is true the difference may be more like +50% or more.
So long as you have enough memory that paging doesn't hurt performance first.
May 7, 2006 8:09:35 AM

Quote:
Could someone tell me if I would see much of a peformance difference by upgrading from the 2.8/400 to the 3.06/533? I believe the 3.06/533 has HT. I have the mobo for the 533 so I can swap it out of the 400 mobo and all I would need would be the chip. I realize it is only a 7% performance gain but I don't know if is actually more given the larger bus and HT.

Thank you.


It's not a 7% performance gain, it's a 7% clockspeed difference. mhz doesn't mean a thing when you're comparing two completely different types of chips. If the 400fsb chip you're describing is a celeron (only quarter of the L2 cache), which i think so, then you're likely to get a whole lot more performance from the 533mhz p4 (you'd get much more performance if you overclocked the thing, tho).

however i could probably be wrong, it could just be one of the older p4 northwoods or something.
but regardless overclock that 533mhz bus for all its worth i say
May 7, 2006 1:46:32 PM

They are both P4 chips and they both have a 512 L2 cache.
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