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pentium 4 @ 1ghz bus w/ 500mhz ram

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June 16, 2004 11:04:40 PM

I am wanting to emulate (to some extent) the setup in this article: http://www.tomshardware.com/motherboard/20030812/index....
They use a Pentium 4 2.6ghz and increase the bus to 1ghz to produce a core clock of 3.25ghz. The 1ghz bus speed runs synchronously with the ddr 500mhz memory bus because the underlying speed of both is 250mhz. I have a few questions pertaining to this setup...

1. Is the AGP/PCI bus speed affected when fsb is increased to 1ghz (unless the motherboard has an option to fix the AGP/PCI bus speed)? If so, does this cause any problems?

2. Does the 2.6ghz p4 require cooling other than the boxed cooler if increased to 3.25ghz(1ghz bus)?

3. I will change this question to make it more clear. In this article: http://www.tomshardware.com/motherboard/20030707/i875p-... and on that page where it begins to list the overview of the motherboards reviewed, each board increases(and in some cases decreases) the CPU clock and FSB by a small percentage. Does this affect the synchronousness between the FSB and the memory bus or is the memory bus also increased by that same small percentage?

4. A motherboard I am considering is the Gigabyte GA-8KNXP. A customer who reviewed it stated that corsair memory conflicts with this board which is the memory I was planning on buying. Is there any truth to this? Also that motherboard comes with a voltage regulator for six-phase operation. I don't understand exactly what this is and I am curious as to what, as far as voltage regulators, is required in this setup.

Thanks for reading all my questions and, also please let me know of anything else important as far as motherboard features, memory or anything else pertinant to this setup.


<P ID="edit"><FONT SIZE=-1><EM>Edited by pddaum on 06/16/04 09:18 PM.</EM></FONT></P>
June 16, 2004 11:13:07 PM

1. The AGP/PCI is effected unless it's selected to fixed in the bios. And yes it will lead to graphics card failures and harddrive failures.

2. The 2.6 varies, my first one did 3.5Ghz with box, my second one did 3.0 with stock.

3. Huh? rephrase that you're not making any sense.

4. I recommend the Abit IS7 or Asus P4P800 if you're into overclocking, and don't need the fancy features of I875P.


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June 17, 2004 12:01:28 AM

When I say boxed cooler I mean the heat sink and fan that come boxed with the retail processor. That, to me, would also be considered the stock cooler. Do you mean the same thing when you refer to boxed and stock also? To clarify the 3rd question have a look at this article: http://www6.tomshardware.com/motherboard/20030707/index...
In the overview chart and in one of the benchmarks it lists the cpu clock for each board reviewed which is initially 3.2ghz, but each board has + and sometimes - a small percentage. I am confused by the variation in clock speeds among the boards and I wonder if it has any effect on synchronizing the system bus with the memory bus. Thanks again.
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June 17, 2004 12:12:06 AM

LOL nono what i meant is i don't understand your question number 3

-How are the cpu core and bus increases that most motherboards seem to exhibit achieved and do they have any effect on attempting to run the system bus synchronously with the memory bus?


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June 17, 2004 12:14:44 AM

I'll try to explain to what i think ur question is.

The CPU has a multiplier, the multiplier multiplied by the FSB gets you the final CPU speed, in the case of a 2.6C, it has the FSB of 200, and a multiplier of 13, 13x200=2600mhz. When you increase the FSB to 250, 250x13=3250mhz.

There's no such thing as a stable clock, it always varies, how much depends on the board, but it won't vary more than 1-2FSB honestly who cares. Unless it's a MSI board, and you set it to adjust itself a lot.

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June 17, 2004 1:02:45 AM

Did you bother to read the entire reply or just the first sentence? I went on to clarify my question number 3 after I asked another question. I don't understand what you mean by "stable clock". What I know is the optimal ratio between the system bus and the memory bus is 1:1. In this case they should both be 250mhz. In this article :http://www.tomshardware.com/motherboard/20030707/index.... they test it at the normal 200mhz. If the Gigabyte board I was considering increases it by 0.12% to 202.56mhz and the memory bus remains at 200mhz then they are not the same and thus are not synchronized. Does each board also increase the memory bus by the same percentage to keep it synchronized with the system bus?
June 17, 2004 1:08:15 AM

Also, you said that the AGP/PCI bus is affected and will cause problems unless the speed is set as fixed in the BIOS. Do most motherboards have that option?
June 17, 2004 1:36:24 AM

Calm yourself please. I have never heard anything about the speeds never being 100% stable. All I know from reading articles is that apparently the system runs best if the bus speeds are synchronized or pseudo synchronized (one being a multiple of the other). I did not think that it mattered how little the synchronousness was off. I thought just the fact that it was off was enough to decrease performance. So the reason I care is so that i can increase my understanding off this. Excuse me for not wishing to remain ignorant.
June 17, 2004 2:03:00 AM

After some careful research 1:1 is not the only way to go on i865pe/i875p system. I've personally tried this, with the original Corsair 3200LL series of ram which can run at 2-2-2-5 against the OCZ PC4000 which runs at 250mhz at 3-4-4-8. the OCZ can use 1:1 ratio on a 2.4C at 250FSB resulting 3.0Ghz, the Corsair can only use a ratio of 5:4 FSB:D ram, therefore the FSB is at 250, while ram is only at 200mhz, however much lower timings. And after benchmarking using Sisoft and a bunch of games, the results were almost identical+-3% which i consider it margin of error. So you could go for some nice low latency PC3200 ram for your i865/i875p system if you're kinda broke.

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June 17, 2004 2:13:01 AM

Well I'm not broke, but I'm surprised that low timings would give such performance. According to that first article I cited the clock speeds were the most important factor and the timings were insignificant, showing no noticeable gains. Also, are you certain that all motherboards with the 865pe and 875p chipsets allow fixed AGP/PCI clocks? The chart on the mobo tsunami article (reviewing 24 865pe/875p mobos) lists all the setting options for AGP/PCI clock for each mobo and not all of them list "fixed" as an option. Another question: What does the "c" represent in 2.4c and 2.6c? I think it represents the core being a northwood with 800mhz fsb, but I'm not sure exactly. One last thing: (to clarify my understanding) If I purchase a 2.6c is there a good chance I will be able to achieve the 1ghz fsb and will it require a cooling solution different from the cooler that comes with the retail processor?
June 18, 2004 4:29:11 PM

Wow, thanks for that amazing link! I guess 1:1 isn't the only game in town on the P4! :smile:


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June 19, 2004 9:59:34 AM

If you are def going to overclock the best board for you would be the Abit IS7 or AI7, both have an AGP/PCI lock. They are very fast and can normally reach 250Mhz FSB(I got to 250Mhz fine on my AI7). The Geil RAM Im using on my board can do 250Mhz with 2.5-4-4-7 timmings, which aint too bad.

In answer to your question yes you are correct about the C. There were 3 revisions of the northwood core, A, B and C. A had 100Mhz FSB (quad pumped=400), B has 133 (533) and C has 200Mhz (800). What ever you do dont buy a P4 with 'e' after the name.

<font color=blue>P4c 2.6@3.25
512Mb PC4000
2x120Gb 7200.7 in RAID0
Waterchill KT12-L30
Abit AI7
Radeon 9800Pro
</font color=blue>
!