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Super Bus Speed

Last response: in Motherboards
June 3, 2001 5:45:49 AM

I have a burning question about the P4 boards.

I'm looking to buy a new motherboard for various reasons, and I want this sucker to fly. I'm considering all the issues with motherboards, such as bus speed, memory, and the chip. I was looking over at this motherboard from Asus, one of their only P4 boards:

I've read the many debates over RDram and DDRam, and the P4 vs Athlon; I just want the best performance with similar prices. I can get the P4 mothebroard and a P4 1.3 for very similar prices to a nice Athlon motherboard and a 1.3 Athlon chip. But to my surprise, the P4 board runs at 400mhz - how are the two even comparable? I know the chips compare differently (Athlon performing better) but why isn't the 233 bus speed now cast aside and stepped on while making one's way to this 400mhz intel chip? Thats like stepping up from a 133 to a 200.

Does the P4 actually run at 400? Do the devices interface at 400, while the Athlon boards interface at 233? If this is the case, then I would gladly go with the P4 board and the RDram, no matter how unpopular. One reason is for the Geforce3, which I believe runs at ~400mhz. Any fast future devices would benefit from such a bus speed. If the Athlon chip runs better, and the ram's are comparble in performance, then wouldn't the 400mhz board be a better investment as all devices now and in the future would run at a higher speed? I can always upgrade the processor or whatever when Intel gets its act together. Also, the ram is running at 800 (RDram) - why would you purchase a DDRram compatible P4 board when they are available if the ram is going to be 233 and the board 400? Would that now lower the board to 233, which I'm sure the P4 would drastically slow down.

What I don't see is why sacrifice so much bus preformance to get an Athlon? Or are the two buses comparable somehow? (I'm just going off the numbers ;-)

Any responses would be appreciated, please don't address DDR vs RDram unless you're talking about how the board somehow, I'm aware of their respective differences =)


-Phil Crosby

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a b V Motherboard
June 3, 2001 7:26:12 AM

The 400MHz simply refers to the FSB, the bus that goes from the processor to the north bridge, and the memory bus. AGP is still 66MHz. The next Pentium4 is sure to be much faster in games than the current version. Right now the T-Bird is still king in games.

Cast not thine pearls before the swine
June 3, 2001 3:02:21 PM

~ I can always upgrade the processor or whatever when Intel gets its act together ~

Sorry, but there doesn't seem to be anyone who expects the current P4 and the Northwood P4 to be slot/socket compatible.

Currently the P4 is so choked that it does not make good use of the RDRAM memory's capability. Also the DDR-SDRAM provides little performance improvement either as it really requires dual channels to perform.

~ I'm looking to buy a new motherboard for various reasons, and I want this sucker to fly ~

Any high-end system you buy today will fly, we are lucky to have so much power! However, if you want to catch the next wave, the Northwood will rock as will the Thoroughbred, there are also new chipsets SiS 735 (already released) & nVidia Crush (24 hours to go!) which are worth considering.

<font color=blue> The Revolution starts here... as soon as I finish my coffee </font color=blue> :eek: 
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June 3, 2001 5:21:44 PM

The whole FSB thing is kind of confusing when you first start to read about it. As far as the Pentium 4 having a "400 MHz" FSB and the AMD Athlon having a "266 MHz" FSB, both are sort of a bunch of marketing crap.

The P4 actually has as 100 MHz bus, which is Quad-Pumped (which I think means that it sends data four times in one clock cycle).

The AMD Athlon has a 133 MHz bus, which is Double-Pumped (or sends data twice in one clock cycle).

This is one of the reasons why an Athlon is faster clock for clock than a Pentium 4, because it's actually running on the faster Front Side Bus.

As far as the devices interfacing at the faster bus, Crashman is right on this one. These bus speeds only refer to the processor to Northbridge to Memory speed, not any speed at which it will connect to your PCI or AGP slots.

Also, you are right that you probably wouldn't want to match a P4 with DDR-SDRAM, because it's always better to have the memory and Processor speeds the same.

Hope that gives you a better understanding...

<i>I don't know anything about computers... but I did stay at a Holiday Inn last night...</i> :lol: 
June 3, 2001 5:24:12 PM

Whatever you do, do not get a 1.3 gHz Pentium 4! If you get a Pentium 4, atleast get a 1.5 or 1.7 gHz. Pentium 4 1.3 gHz is an extremely slow processer when compared to an Athlon 1.3 gHz. When you see that an Athlon 1.3 gHz performs on par with a 1.7 gHz Pentium 4, a 1.3 gHz Pentium 4 simply isn't worth it, and you'd probably be able to get an Athlon 900 or so that performs the same as the 1.3 gHz Pentium 4. In terms of your other questions, here's what I can answer.

The P4 runs at 400 mHz, which in reality is a quad pumped 100 mHz. So, the bus speed between all the peripherals in the system is 100 mHz, but the processor clock is 400 mHz. Similarly with the Athlon, the processor clock is 266 mHz, which is actually a double pumped 133 mHz front side bus. So, the Athlon bus is actually faster than the P4 bus in terms of the interface between the peripherals of the system (video card, memory, etc.).

The fact that the GeForce3 runs at 400 mHz has no bearing on what bus speed the rest of the system runs at.

About RDRAM bersus DDR SDRAM. Sure, the RDRAM is at 800 mHz, but it only has a 16-bit wide data path, while SDRAM wuns off of a 64-bit wide data path (or is it 128-bit wide?). A single channel RDRAM solution can offer 1.6 GB/sec badwith, while a dual channel RDRAM solution offers 3.2 GB/sec badnwith. PC2100 266 mHz DDR SDRAM can offer 2.1 GB/sec bandwith in a single channel solution (which is what most DDR Athlon chipsets offer). However, the new nVidia nForce chipset has a dual channel DDR SDRAM channel, which offers 4.2 GB/sec of bandwith, much higher than what RDRAM can offer the Pentium 4. But, for the boards to operate with dual-channel memory, you need to have 2 memory banks full (so for 128 MB RAM, you need 2 memory slots each filled with a 64 MB stick).

The numbers are misleading, but in reality the Athlon has a faster BUS, now faster memory with higher bandwith, and an Athlon runs far faster than a Pentium 4 at the same clock speed. Even though the numbers seem to favor the Pentium 4 at first glance, looking deeper shows that they truly do favor the Athlon. And in reality, to get an equally performing Pentium 4, you will need to spend a few hundred dollars more, as the pentium 4 itslef, motherboards, and RAM are all more expensive for the P4 than the Athlon.

"Trying is the first step towards failure."
June 3, 2001 5:53:54 PM

Wow, thanks guys, those were just the answers I was looking for. They answered all of my questions. I didn't know that the P4 board actually ran at 100mhz, and that the processor components were just quad pumped. That sucks =) Excluding processors, when it comes down to it, I would much rather have the 133 than the 100! The ram for P4 is still alluring, but if what the post says above me is true, then DDR transfer speeds will smoke RDRam's transfer speeds with this "new" motheboard. Hopefully in combination, they will be cheaper than the RDram alternative (I know DDR is cheap, but is the new DDR mobo cheap)?

I've also been reading some huge benchmark articles comparing the P4 and the Athlon (, and I'm definatley in favor of what the Athlon can do. It seems Intel has a tremendous amount of resources to expend, pulling a lot of new technology into the P4, but they botched so many aspects of it and made it impractical (Sort of like a 300$ PC game with incredible graphics that runs at 2 FPS or something). Anyway, I hope this new Nvidia board is cheap as well and can support DDram with 2x the transfer rate! That would make my day (I was looking for a reason to start supporting DDRam, because up until now it looked like RDram would have the better technology future). If anyone has any information on this new board, could they please post a URL, because I've tried checking it out in a search engine and everything seems pre-mobo release.

Thanks for everyone's help.

-Phil Crosby