View Full Version : Optimal MGATweak o/c setting for vanilla G400?

10th June 2000, 10:35
I'm interested to know what System PLL Clock speed G400 you are able to overclock to using MGATweak on a stock-standard G400 with no additional cooling system (e.g. fans, etc).

The default speed is 252MHz. I picked a number out of the air (well, 10% above default) and set MGATweak to 276.75MHz System PLL Clock (184.50MHz Memory Clock speed). I got a nice boost in 3DMark2000 from a score of 2813 to 2991, and Quake III Arena's Timedemo on High Quality went up from 41fps to over 45fps without any reduction in graphics quality. Did I hit jackpot here?


My system specs:
Intel Pentium III 650MHz
Asus P2B motherboard
128MB PC-100 SDRAM
Matrox G400 32MB SH @ 184.50MHz, running ParaKnowYa's driver pack v1.5
Creative Sound Blaster Live! Value with latest drivers
Quantum Fireball ST 6.4GB & 4.3GB
I/O Magic 8X DVD-ROM (region-free)
Kenwood 42X TrueX CD-ROM
CTX PR711 17" Monitor, currently running 1024x768x32 @ 85Hz
Windows 98 (not SE)
3DMark2000 default benchmark score: 2991

11th June 2000, 06:15
Hello WarFlail!
I seem to be stalking you through these boards!

I never had much luck overclocking my vanilla G400, until I set the 'Minimum Read Precharge Delay' from SLOW to FAST. This enabled me to get up to 155mhz (310 PLL clock) with no adverse effects - just obesely boosted performance.
Keep tinkering, you should get much more out of your G400 - just know what to look for when you're pushing it too far!

12th June 2000, 07:41
LOL! Everywhere I go, Rik, you seem to be there! :-)

Thanks for the tip. I did get over 3075 on 3DMark2000 after increasing the System PLL Clock to 288MHz, but beyond that I started to see little yellow dots here and there (i.e. graphics degradation). I might try again with the Minimum Read Precharge Delay set to FAST, though.

One thing I did notice in the 3DMark2000 test, though, was that the more I cranked up the G400, the jerkier one of the tests became - that one with the Mad Onion logo slowly moving about the screen like you're on hallucinogens... Again, I will have to try this again with the new setting, to see if there is any difference.



12th June 2000, 09:51
I started experimenting a bit more with MGATweak and found that a System PLL Clock speed of 270MHz has the best compromise between speed and smoothness. Any higher and the fill rate benchmarks for 3DMark2000 end up looking a little jerky (like some parts of the screen are refreshing ahead of the others). This gives me a score of 2869 Marks - not great but acceptable, I think... this setting gives me a little over 47fps on Quake 3's Timedemo (High Quality).

I tried changing the Minimum Read Precharge Delay from the default SLOW to FAST, but saw no apparent improvement - if anything, the speed suffered by around 3-4%. At 288MHz, I scored 3080 Marks on the default setting, but only 2998 Marks with setting on FAST.

I am somewhat wary of tinkering with the rest of the settings on MGATweak. I think that playing with just the System PLL Clock speed would yield the biggest performance boost, anyway.


1st September 2000, 12:16
My settings are:
System PLL Clock: 300.00 MHz
GCLK: 150.00 MHz
MCLK: 200.00 MHz
WCLK: 150.00 MHz
SDRAM/SGRAM Settings (starting at CAS Latency): 3, 1, 3, 9, 4, Fast, 1, 1, 1, 0.2, 0.2, 1985
These settings seem to be OK, tough I see some yellow pixels sometimes (not very much, maybe 5-10 every +/- 5 seconds).

edit: I use a small fan

[This message has been edited by sir5 (edited 01 September 2000).]

1st September 2000, 19:35
If you choose to play with memory optimization, you should find out the optimum settings for all of them. If you only change Memory Read Precharge Delay from SLOW to FAST while leaving others unchanged, you will likely see a performance drop given the same SYSPLL. It's because Matrox video BIOS/Powerdesk does change the memory timings to be faster than the chip specs defaults. Please read MGATweak userguide for more details in SGRAM optimization.

I am somewhat wary of tinkering with the rest of the settings on MGATweak. I think that playing with just the System PLL Clock speed would yield the biggest performance boost, anyway.
No. While increasing SYSPLL does give the best boost in performance, having the option to trade faster memory timings for higher SYSPLL can yield even better performance than tweaking the SYSPLL alone provided you know how to play with them. While not every G400 vanilla is capable of MAX speed especially those with 6ns SGRAM, the option to tune memory timings gives better chance to achieve that.

7th September 2000, 09:55
My G400 SH 32 does core 150/mem 200 (PLL 300) with no problem (no screen garbage or jerkiness), and I haven't got to tinkering MGATweak's memory options yet. Obviously have to learn them, as the card might go somewhat higher than this, especially as I now have a nice 90mm fan on it. Just need to find suitable memory heatsinks :)

But this goes up to eleven.