G400 AT 133MHZ FSB

[J Fitch]

Anyone had experience with the G400 running at 89MHZ AGP 2x with 133MHZ FSB on a BX Board? Can it handle it?

[Maggi]

AGP2x DIME at 83.3MHz

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Cheerio,
Maggi

I used to have some posts in my record and hopefully some of the guys 'n' girls will still know me and my system ...

[Arron]

A dumb question, I'm sure, but this has been nagging at me for a good while now...

The G400 is AGP 4x ready, so Matrox say. AGP 4x runs at 133MHz. So my question is, will the G400 work at 133MHz using AGP 2x?

On my Asus P2B it is possible to set the AGP clock as either 1:1 or 2:3, what would happen if I ran my system at 100MHz FSB with 1:1 AGP and a G400 in my system? Could it do it?

[Buuri]

I don't know, but at least AGP bus pins are different when going 4x. (some of their meanings are different)


B



[This message has been edited by Buuri (edited 07-14-99).]

[neo]

Hi Arron, I've been told that the default operating bus speed for the AGP Bus is 66MHZ. This is whether you are at APG 1x, 2x, or 4x. The closer you can get to a 66MHZ Bus the better off you will be in terms of video problems. I wouldn't recommend using an AGP 100MHZ bus.

-neo

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Asus P2B-F, 532MHZ Pentium II (4x133 at 2.4v), Global Win VEK12 hs/fan, 128MB Micron PC133, Maxtor 4GB, SB AWE 32, Creative DVD 2x, Mitsumi CDR 2x/8x, Sony Trinitron 17", Old Matrox Video Card, and a redhead with a pair of 36Cs (O/Ced to 38Cs)

[Gurm]

The problem here is not the "speed" of the AGP bus, it's how that speed is obtained. So for example, saying that the AGP 2x bus runs at 133Mhz, which is the "speed" is misleading, because it's really 2x66Mhz.

The 4x bus should run at 266mhz (4x66mhz), although they may turn around and run it at 2x133... but that's doubtful. Right now, there isn't enough RAM available anywhere that will reliably handle 133mhz FSB. Even the new 133Mhz RAM only goes up to about 129 without super-cooling. Go figure.

The other problem is tolerances. If you start taking your AGP bus to 75mhz, for example, that's 9mhz out of tolerance. That's... err... 14% outside of the norm. I'm sure most if not all cards are built to withstand certain stresses, but 14% may be the upper limit. If you insist on running the AGP bus at 83mhz (26% out of tolerance) or 100mhz (51% out of tolerance) you are just asking for trouble with the signals.

Remember it's not really 0's and 1's like everyone says - it's rising and falling edges of a pulsed digital signal at 5VDC.

- Gurm

[Genom]

Hey Neo, I got the same exact MB as you (P2B-F) and was wodnering, how did you change the voltage on the CPU? If I could get to 2.05 I could get my CPU running at 580Mhz but as far as I saw there's no way to do this. Pleas elet me know ok?

Danke.

Soon as I can do that I'll be over 9000 cpumarks

Woohoo!

[Gurm]

Genom,

As I recall there is/was a program specifically for ASUS P2B boards that let you do a soft-adjust of things like Voltage and FSB, etc. etc.

I forget what it's called, but if you go to one of the hardware sites like HardOCP, I'm sure you'll run into it fairly quickly.

- Gurm

[overclokked]

As far as I can tell, my G400 is running pretty stable at 103mhz FSB....you guys are saying I should pull it back down to 69?

[Buuri]

Gurm,

Do they use Manchester or Differential Manchester coding? Or perhaps something else?

(hehhe.. just wanted to show off with my very little knowledge of "pulsed digital signal"s..)


B

[Arron]

Hey overclokked,

is that with 1:1 AGP bus speed?

This is where my curiousity lies. You see the BX chipset supports AGP memory transfers at 1:1 speed; the G400 supports 133MHz transfers; so, if you put the two together, maybe you could run the G400's AGP clock at 100MHz. It would make large texture transfers 50% quicker in theory.

[neo]

Gurm, I would like to reply.

"Right now, there isn't enough RAM available anywhere that will reliably handle 133mhz FSB. Even the new 133Mhz RAM only goes up to about 129 without super-cooling. Go figure."

I have Crucial PC133 RAM that runs prime95 stable for 24hours (didn't try it longer) at 133MHZ FSB. I'm not sure where you got your info, but this seems stable to me. It also runs at FSB=140 for a short time, albeit not reliably. My current system configuration is FSB=133, stable for weeks now.

"The other problem is tolerances. If you start taking your AGP bus to 75mhz, for example, that's 9mhz out of tolerance. That's... err... 14% outside of the norm. I'm sure most if not all cards are built to withstand certain stresses, but 14% may be the upper limit. If you insist on running the AGP bus at 83mhz (26% out of tolerance) or 100mhz (51% out of tolerance) you are just asking for trouble with the signals."

I know people that run an 89MHZ AGP bus without a glitch. The new TNT2 cards have plenty of bus flexability, as does the G400 (from what I've heard at MURC). Trouble with the signals doesn't mean it will not work, as can be seen with the newer video cards.

Genom, the P2B-F does not support soft voltage changes. If you want to change the CPU core voltage you have to tape pins (the CPU contacts to the MB). This isn't as hard as it sounds. Let me know if you want more info, I'll give you some websites to look at.

-neo



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Asus P2B-F, 532MHZ Pentium II (4x133 at 2.4v), Global Win VEK12 hs/fan, 128MB Micron PC133, Maxtor 4GB, SB AWE 32, Creative DVD 2x, Mitsumi CDR 2x/8x, Sony Trinitron 17", Old Matrox Video Card, and a redhead with a pair of 36Cs (O/Ced to 38Cs)

[Buuri]

neo,

Just a point that by overclocking it that much you can end up with lower performance. It's important to oc a step by step and check how it does.
Have the people you know bothered to check if they even run any better with 89 than when they would go with 75 bus?

The fact that it may work may just be due to better error resistance. It doesn't mean that it will perform better.


B

[arbymo]

Genom : go to www.arstechnia.com .. they have the howto for taping processor pins to change the voltage


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GigaByte 6BXE, celeron 300A@464, 128 PC100 RAM,
G200 8 M SD @112.5 core. driver 4.51, bios 2.3.

[Gurm]

Arron - there is no way, short of a miracle from God, that 133mhz will work with a 1/1 AGP/FSB ratio. Just won't happen. When the G400 specs say it can do 133mhz transfers, it means at 2x66mhz. The AGP bus runs at 66mhz base clock. Even in 4x mode. They won't commit to saying whether or not the G400 does 266mhz transfers in 4x mode or not... for technical reasons (like no 4x boards are out yet).

neo - As Buuri pointed out, you can end up hurting yourself. Here's why:

1. Many motherboards automatically switch you to 2/3 AGP/FSB when you clock up over 75mhz or 83mhz. A 2/3 ratio at 75mhz means you're UNDERCLOCKING your card by 16mhz. At 89mhz (your target #) the card would still be underclocked by 11-12 mhz.

2. Even if you are running at 1/1, you may discover that the following happens... the signals get out of sync, and the card compensates by adding wait states. Therefore, the card acts as though it is in 2/3 mode whether you have it set that way or not. I think most new cards have this built in to hardware. What is odd is that it works better some times than others. Some people get certain cards to run at 83mhz fsb 1/1 and others it just crashes.

To be honest, I haven't had a setup that reliably overclocked in about 6 months (and I change my rig weekly). I decided to skip it and go for stability. So I got a P3-550, a G400 DH, and twin IBM hard drives (quiet, stable).

- Gurm