How to overclock 32mb G400 single head?

[The Destroyer]

I've got a 32MB Matrox G400 Millenium single-head, not Max.

How do I overclock it? Should I use MGATweak or MatroxTweak?

And what setting should I use? Can someone with the same card as me tell me what settings they are using? And once I've made the settings with that utility, do I have to have that utility opened all the time?

[anid]

As I said in the Ars forum, use MGATweak. Read the pdf file, try it out, and report back. Or just see cannyone's post a few threads down.

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"I wrestled with reality for 27 years and I'm happy to say I finally won out over it."

[The Destroyer]

I looked at a few more threads in the Matrox Users forum. Couldn't do what others were doing but I have managed to up my PLL Clock to 381 MHz, my dividers are 2.5/2.0/2.5

Is lower divider better or is higher better?

Can you explain to me what is the System PLL Clock, vs the Graphics Clock?
Which is better? A high PLL clock or a high graphics clock, or memory clock? ie If I were to lower the PLL clock so that I could lower the clock divider and get higher graphics and memory clocks, is that better? or does it depend on how much I lowered the PLL clock and how much gain I got on the other two clocks?

For the clock selection, what is the difference between SYSPLL and AGPPLL?

[CannyOne]

Hi Destroyer,

As far as I understand it the System PLL is the clock from which the other "clocks" get their speed. I'm not completely sure if it's just a "metric" or an actual crystal on the card. Regardless, when I attempted using either the AGP clock, or different dividers. The results weren't "pretty". So without other suggestions I've decided to simply go with "what works". Sorry I don't have better answers for you.

[kjliew]

System PLL - clock source for GCLK, MCLK and WCLK. All system performance related clock are derived from system PLL.

AGP PLL - clock source for generating AGP 2x clock. AGP is source synchroneous, the master must generate the clock for transfer. AGP PLL can be re-route to GCLK, MCLK and WCLK on G400, but not recommended to be used.

[The Destroyer]

Well like I said, I've increased my System PLL clock to 381MHz.

The Graphics Clock is at 152.4, the Memory Clock is at 190.5, and the WARP Clock is at 152.40.

I read that the G400 Max has factory defaults of PLL=301.5, GCLK=150.75, MCLK=201.00, WCLK=150.75.

As you can see, my Memory clock is lower than a G400 Max's default. How big of a deal is this? Does it mean that my card will be faster than a G400 Max in certain things but a bit slower in others?

As you can tell, I basically have no idea what the memory clock and the graphics clock do! Is this analogous to overclocking the CPU and having to lower the cache divider?

[anid]

I'm not sure about the G400, but I think there is a difference in the RAM chip speeds between the Max and "vanilla" versions - 4.5ns for the Max and 5ns for the vanilla. Is this correct, guys? It's been a while and I don't really remember. If it is then somewhere around 200MHz would be about the max for your mclk. Try the 1.5 mclk divider and see if the card will handle it (with the 380 sclk). The mem speed will play a pretty significant role in determing when your card hits the fillrate limitation, so try to find out exactly how high you can get the mclk - you may be better off going with a 1.5 divider to get the higher mclk, even if it means a lower sclk. Try it both ways, bench it, and see.
Let's see if I have all this straight. The sclk is the master clock generator, it (along with the dividers) determines the speed of the other clocks. The gclk is equivalent to the CPU speed - it determines how quickly the card can execute the instructions. The mclk is like the FSB - how quickly the data can be moved back and forth to the bus. So, you do want a balance between the gclk and the mclk. If the mclk is too low (compared to the gclk), the chip will be sitting idle while the bus is choked with data. If the gclk is too low (compared to the mclk), the bus won't be loaded while the chip strains to process requests. I'm guessing that it would be best to get the mclk as high as you can, even if it means slowing the gclk a little. But, if your mem speed is already maxed (at 190), you may already have the best you can get out of it.

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"I wrestled with reality for 27 years and I'm happy to say I finally won out over it."

[dsp]

Actually Anid, the RAM chip speeds are as follows 5ns for the MAX and 6ns for the vanilla versions unless youi get lucky and get a 5ns vanilla. I agree with you Anid, if the memory isn't running fast enough (IE. GeForce SDR and DDR) the memory can't recieve info as fast as the core is sending it, thus slowing the whole application down to the speed of the RAM.

DSP

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AMD K6-2 350@400MHz
128MB Generic PC-133 RAM
13.6GB Maxtor 7200RPM Hard Drive (Yaaa!!)
Toshiba SD-M1212 6X DVD ROM
ACER 2X/2X/6X CD-RW
SB 128 PCI
Matrox G400 32MB Dualhead Vanilla @ 157/210/157
15" Daytek 1531D
PD 5.52
Win 98SE
10Base-T Ethernet card
DSL (Yahoo!!!!)



[This message has been edited by dsp (edited 02 May 2000).]