Memory, CPU, & FSB timings

  G_NoMoney 00:11 11 Jun 2003

I've researched this subject to death and it still confuses me. On many mainstream Pentium 4 platforms, I see the CPU & motherboard specs which claim FSB support for 533 Mhz. Now, assuming we're not using dual-channel DDR memory (which many boards don't support), and assuming we install PC3200 (DDR400) memory, aren't we going to bottle-neck the CPU since it is capable of pulling data off the FSB at a rate of 533 Mhz while the memory can only supply it at a rate of 400 Mhz??? What is the advantage of buying a CPU (or motherboard) with this FSB rating if the motherboard only supports up to DDR400 memory? Why would a motherboard company even design a board this way? Is it just to reap the benefit of raising the system clock from 100 Mhz to 133 Mhz???

  davidg_richmond 01:17 11 Jun 2003

There is always one part of the system that speeds ahead of the rest, and more than one part that slows down the others. This is evident in the front side bus speed being much faster than the memory bus speed, and by the fact that PCI technology is still behind the FSB in performance by a huge amount.

That said, you can buy Rambus-compatible motherboards that allow 800Mhz memory modules, and AGP 8x boards and graphics cards that run at 533Mhz, so these two combined offer a vast amount of power to high-end users such as gamers and graphic designers/3d modellers. Rambus memory is still very expensive though, and not widely used.

If you want the best performance out of a 533Mhz bus without spending on Rambus, get PC3200 memory well over 512Mb, and an AGP 8x graphics card. You will find that the system runs smoothly enough! During gaming, for instance, the memory bus is supplying data to both the processor and graphics processor, and not engaging either 100% of the time. The processors are often still trying to process the data while more is being supplied during high-end gaming.

  Mysticnas 02:09 11 Jun 2003

they will release better equipment at a later date. There is no doubt at all that most if not all of the companies have better technology developed than what is out on the market. The way that they will make more money is if they release it slowly. here's a few examples...

Intel CPU's 2.4/2.53/2.66/2.8 were all released within short periods of each others. Now, there's isn't much noticalbe different between those clock speeds, only a few 100Mhz. but as opposed to going straight from 2Ghz to 3Ghz they slowly released the CPU's so people who want the fastest will go out and buy the new CPU!

Matrix 2/3. They must have saved big $ making these two films together. However this saving is not reflected to the consumer. Instead they are making more profit out of it, or at least they intend to, it all depends on how well they do at the box office. You see the released Matrix 2 just recently, but Matrix 3, although it is already made, they aren't going to release til November sometime.

No matter what people say... Money "DOES" make the world go round!!! :o)

  Mysticnas 02:14 11 Jun 2003

PCI slow? the bandwidth on my mobo between PCI bus speed is 1Ghz. I thinks thats the transfer speed between south and northbridge.

  davidg_richmond 02:42 11 Jun 2003

Mysticnas - PCI only runs at 33Mhz itself (due to be increased with the quite different PCI Express technology coming out shortly).

  G_NoMoney 02:48 11 Jun 2003

I guess a picture is worth a thousand words here for me. I checked out the following link to get more info: click here
I was under the impression that somehow the system bus was a direct link between CPU & memory, hence there was a lot of confusion about how DDR400 memory which runs with a clock speed of 200 Mhz could work with a Pentium 4 FSB of 533 Mhz running with clock speed of 133 Mhz. Thanks for all of your input on the subject!

  davidg_richmond 03:23 11 Jun 2003

No, as you may have found out the Front Side Bus simply links the processor to the 'North Bridge' (a controller chip). The Memory Bus then links to the North Bridge, as does the AGP bus. Then the North Bridge links to the South Bridge where all the slower hardware goes (PCI, Parallel, IDE etc). So that's where the benefit of fast memory, FSB, and AGP comes in especially with games.

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