9800XT Vdd mod

[bmg]

I figured I'd pass on a little info on the 9800XT Vdd mod. The 9800XT uses the same ISL6522 controller as the 9800pro. Resistor values have changed however. The FB input is pin 5 and ground is pin 7. If the resistance from pin 5 to ground is R2 and the resistance from the Vdd output to pin 5 is R3, we get Vdd=.8x(1+R3/R2). R3 has a code of 13B, which is 1330 ohms. R2 has a code of 73A, which is 562 ohms. This gives a default Vdd of 2.69V. I measured 2.68V. The ram is spec'd at 2.80V+/-.15. Notice that the default voltage is actually below the 2.80V nominal voltage spec for the ram. Connecting a 10k pot from pin 5 to ground gives us:

Rpot/Vdd
9.8k/2.80V
5.0K/2.90V
4.0k/2.96V
3.5k/3.00V
3.0k/3.05V
2.5k/3.12V

Vdd is generated from the standard motherboard 3.3V supply, so I suspect it would be difficult to fry the ram (Vdd max should be less than the 3.3V supply), but I'd still be careful.

In the picture the yellow/black pair is for Vdd monitoring and the red/black pair is where I attach the pot. I've got enough air moving in my case that the backside plate does an adequate job of cooling the ram, but I'll probably eventually switch to regular heatsinks. BTW, the 3 pin connector actually fits though the hole in the plate, so the soldering was done and then the plate reattached. I'll most likely just replace the 562 ohm resistor on the board with a 487 ohm (for 2.98V) and then remove the wires.

[bmg]

Here's a picture of the front:

[luihed]

What kind of clocks are you getting before and after the vmod?

[Evil_Spork]

your insane. 'nuff said.

[charlie]

niiiicceeeeeeeee.....
looks fun!
RESULTS Please!

[bmg]

The 9800XT's ram is much better than my 9800pro's, but the core isn't much better (nothing a bit more voltage wouldn't improve I suspect). I just ran through 3DMark2001 at 486/412 with no artifacts. That's with Vdd=3.00V. At 486/419 or 493/412 I'm starting to see minor artifacts, but of course the test runs fine. If I run the core above 479 with 3DMark03 I start getting small white dots in Nature. I have a spot in Unreal2 that I use for "Sparkle" testing. With 4xAA and 8xAF-quality it'll show sparkle when nothing else I've found will. With those test conditions I start seeing minor sparkle at 378 memory. 384 shows quite a bit of sparkle in this test, but it looks clean everywhere else. That's why for gaming I just run 472/378 (normally 4xAA and 8xAF-Quality). The GPU is cooled with room temperature water.

[xDUCK]

Looks like they bumped up the memory subsystem!

Just to be clear - we are talking Vddr here, yes? Or is VDD something different?

[charlie]

As I expected...420 on the mem with a slight voltage increase.
I bet this mem will go 440+
Jason, this should be the card for YOU, with the mem oc luck you have...
C

[bmg]

Originally posted by xDUCK
Looks like they bumped up the memory subsystem!

Just to be clear - we are talking Vddr here, yes? Or is VDD something different?

Yes, Vdd is the ram core voltage and Vddq is the io voltage. Vddq should never be greater than Vdd, according to the ram spec.

[charlie]

BTW Bmg,
Thanks for the clear detail and instructions on the new hardware. It's refreshing to see as some of the guys here hide their new hardware and don't give any tips on it until they've exploited it themselves...
C

[STEvil]

Can we get a screenshot of this location?

[bmg]

Originally posted by STEvil
Can we get a screenshot of this location?

The worst spot I've found is right at the beginning of the repair mission in Unreal2 (I forget what it's called, I'll check it tomorrow). Just turn to the left and look at the ground after Isaak stops talking. It's unclear to me exactly what makes this spot so bad. You'll need to push your video ram hard, turn on high AA and AF, everything maxed. 1024x768. You probably need a reasonably fast cpu to push the video card. I've seen this with the 9700pro, 9800pro and now 9800XT. One of the old Q3 maps used to be my standard sparkle test, but this is much worse.

Let me know what you find.

[Manoj]

bmg:

Did you get Half Life2 together with your card?

[xDUCK]

Originally posted by Manoj
bmg:

Did you get Half Life2 together with your card?

ROFL. Half-Life won't be released until February 2004. I highly doubt he got HL2 with his XT.

[GJ]

half-life...

http://www.overclockers.co.uk/acatal...agx_2d019_2das

it is on preorder,with halflife2

[GJ]

sorry,you just get a coupon for it,so you can get it free when it will be released

[Manoj]

Originally posted by GJoz
sorry,you just get a coupon for it,so you can get it free when it will be released

Then I guess the only main advantage the RAdeon 9800 XT will have is in the benchmarks.

[GJ]

http://www.3dchips-fr.com/News/actua...200310092.html

96pro and xt sure got a difference.

[bmg]

Originally posted by GJoz
sorry,you just get a coupon for it,so you can get it free when it will be released

Just a coupon. The box says it's good for the full single and multiplayer game. I can't remember the details, but basically the game will be shipped to you (or you can download using steam) and the coupon has the activation key. http://www.ati.com/gitg/promotions/h...e2/coupon.html

[macci]

Nice info there bmg

Whats the Vddq voltagelevel on this card?
ATI lowered it from like 2.8V to 2.65V when they went from R9700pro to 9800pro so is it even lower on this card?

Have you tried mem at 3.3V or higher yet to see if incresaeing it past 3.12v gives any extra boost?

[saaya]

3.0=410
3.1=420
3.2=430
3.3=440 i guess

whats the max vddr you guys would run 24/7?

[bmg]

Originally posted by saaya

whats the max vddr you guys would run 24/7?

That's exactly what I was wondering. I'm sure 3.0V is fine since the 24/7 spec covers up to 2.95V. I'm guessing 3.1V might be ok 24/7, since it's only 5% above 2.95V. What's everyone's opinion?

[QuadDamage]

well, i don't know but at 4.1V it won't run for longer than approx 24 hours benching. I have first hand experience

[STEvil]

24 hours at 4.1v... wonder how long it would go for 24/7 @ 3.6v? heh..

[bmg]

Originally posted by STEvil
24 hours at 4.1v... wonder how long it would go for 24/7 @ 3.6v? heh..

I'm still a coward and running at 3.0V. Actually,3.15V is the max I can get. I'd probably need to boost the 3.3V level of my system power supply to get more.