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Venturi
03-30-06, 07:01 AM
I have a pair of the EVGA Super OC 7900gtx SLI, and I ran Lost cost 64-bit vid stress test, HL2, Painkiller, X2, as well as doom 3 benchmark and the Q4 1.1 smp benchmark.

I also have a pair ot evga 7800gtx 512, SLI. With a vga bios clock each of 575/1750

The question:

At 2560x1600 sli, with the same eye candy settings, why do the 7900gtx get the snot kicked out of them by at least 10-15 frames per second in every scenario?

If I put the 7800gtx 512 back down to their original bios - they still best the 7900gtx by a couple of frames in EVERY scenario.

With a default core clock of 550, why do the 7800gtx 512 outperform the 7900gtx with the faster clock?


What gives? Pissed!!!


Further:

The 7900gtx WILL lock up occasionally after 15-20 min of play time or at least start giving screen curruptions on textures - 2560x1600

Additional observation: The 7900gtx DOES outperform the 7800gtx 512 at any LOWER resolution below 2560x1600. But at 2560x1600 the tables turn, Furthermore the higher you go with Transparent, or AA or AF - the greater the lead the 7800gtx512 has over the 7900gtx.

Will some kind soul please tell me the truth and WTF?!?!?!?!?


Signed:
Confused and pissed.

MUYA
03-30-06, 07:08 AM
ROPS limited....possibly

jAkUp
03-30-06, 01:10 PM
Hmmm, I saw another comparirision that showed the 7800GTX 512 and 7900GTX at the same clocks, to see which design was more efficient, and the 7900GTX was a hair faster.

Venturi
03-31-06, 10:28 AM
I'm assuming that if there a lot of ram, multiprocessors and plenty of power - which cards are better at the ultra-high resolution? While they can be neck and neck sometimes, its when the demand and eyecandy go up, the 7800gtx512 seems to pull ahead. Also with a simpleoverclock to 575/1750 on the 7800gtx512 SLI, the evga 7900gtx gets bested by the equivalent 7800gtx512.

In a single CPU with 4 GB of ram and win 32, the 7900 is 1-4 fps faster than the 7800.
In the multiprocessor, win 64, 16GB ram, scenario, I can't get the 7900 to best the 7800gtx512 with the slolwer clock speed.

Seems that if thay could have given the 7800gtx the same clocks as the 7900superOC, then the 7900 would have a clear lead.


There is something inherently elegant about the performance of the 7800gtx512. The NVIDIA driver set is maybe milking the 7900 to a further extent but it does not make use of the faster chip. Or maybe the 7900gtx is a lesser build that is simply clocked faster.

In a nutshell, I don't see the 7900gtx as a step up over the 7800gtx512. I have returned the 7900gtx and gotten my money back. Sad, but I was originally given the impression of much greater performace.


2nd, and the real reson for the cards being returned - they keep locking up at the 2560x1600 resolution whenever I have more AA and AF than 2x 2x.
The temps never seem to get very high but the cords grind to a halt or develop screen curruption?!


There is one place that the 7900gtx wins by a wide margin over the 7800gtx512 - 3dmark06. I can only speculate the reason for that

Venturi
04-04-06, 07:23 AM
Not to beat a dead horse, but this shoud give some light to my frustration:

On the same home PC (check sig) with driver 84.21

evga 7900gtx SLI (superclocked)
H2 Lost Coast HDR 64-bit, at 2560x1600 with 8xAA, 16xAF, full reflections etc. :
141 FPS

evga 7800gtx SLI 512
H2 Lost Coast HDR 64-bit, at 2560x1600 with 8xAA, 16xAF, full reflections etc. :
159 FPS


with the other 82.12 driver the numbers were lower on both cards but the gap was about the same. 82.65 gave the 7800gtx over 162fps, but the 7900 would lock up before the test was concluded.


Something is up. Wish I knew what the real difference was between the 7800gtx 512 and the 7900gtx.

(remember the default clock of the 7800gtx is only 550)

I've bought and returned to sets of the SLI 7900gtx and in ALL instances I am having random lock ups. Its not a power issue for two reasons: 1, the 7800gtx 512 uses more power than the 7900gtx, and 2, I have dual 850Watt power supplies with 4 seperate rails each.

Its not an OS issue or rig issue because the lock ups do not occur with the other cards, its not a temp issue because the temps stay in the green and on occasion just a bar in the yellow,

All is left is an architecture issue on the 7900gtx.

so what gives?

Any real information would be most appreciated.

Dazz
04-04-06, 12:19 PM
It's to with either, One the 512MB 7800GTX has more memory bandwith or two the 512MB has more agressive memory timings. Can't say why the 7900GTX cards lock up for.

OWA
04-05-06, 07:44 PM
While I still had my eVGA 7900 GTX Superclock (690/1760) I did a few comparisons between it and the BFG 7800 GTX 512 (580/1750). These were my results but it was under XP-32.

7800 vs 7900 at 1920x1200 4xAA/16xAF HQ

CS:Source 134.11 vs 149.73

FEAR: 19/34/81 (22%/58%/20%) vs 20/38/90 (9%/67%/24%)

HL2: Lost Coast (timedemo): 40.93 vs 46.89

HL2: Lost Coast (stress test): 68.68 vs 77.4

X3 Reunion Demo benchmark: 41.17 vs 45.25

3DM05: 9939 vs 11525

3DM06: 5636 vs 6376

Unfortunately, that was all I got a chance to run before sending it back.

betterdan
04-05-06, 08:33 PM
Why did you send it back OWA if it was quicker? Did it have the freeze up problems?

Razorfinger
04-05-06, 08:40 PM
The 7900GTX uses less power than the 7800GTX and has a small die size with a smaller core. The pipes and shaders are about the same. But I think the 7800GTX 512 has faster memory, meaning the 7800GTX 512 has more memory bandwith (54GB/S vs 51GB/S). At such high res, alot of data has to be moved. But at lower res, the 7900GTX wins because it has better a fill rate and is not bottlenecked by memory bandwith.

MUYA
04-05-06, 08:46 PM
Really I thought that the memory paired with 7900 GTXs were clocked higher than 512MB 7800 GTX's. Maybe its what Dazz said, latency of the memory?

Venturi
04-06-06, 07:42 AM
OWA

your results are consistent with mine at that resolution. It is at the high rez 2560x1600 that the 7800gtx 512 takes over the 7800gtx.

The truth is probably this:
7800gtx512 has a greater architecture on the chip, doing more calculations per cycle.
The 7800gtx has faster memory and possibly more bus.

The 7900gtx is a lesser architecture chip but makes up for it with more than 100mhz over the 7800gtx.


If I clock the 7800gtx 512 to 590/1780, fully stable, it outperforms the 7900gtx also at the lower resolutions.


Conclusion: the 7900gtx is not necessarily a better card than the 7800gtx512, however it is a more cost effective per performance card and hence has greater value.

The real question:

WHY NOT PRESERVE THE 7800GTX512 ARCHITECTURE BUT AT THE DIE SIZE AND MHZ OF THE 7900GTX???

Silly me, that's what I thought they were going to do with the 7900.

aaronjb
04-06-06, 09:16 AM
The truth is probably this:
7800gtx512 has a greater architecture on the chip, doing more calculations per cycle.
The 7800gtx has faster memory and possibly more bus.

The 7900gtx is a lesser architecture chip but makes up for it with more than 100mhz over the 7800gtx.

Could you elaborate on what you mean by "greater architecture" and "lesser architecture"?

OWA
04-06-06, 11:47 AM
Why did you send it back OWA if it was quicker? Did it have the freeze up problems?
Mostly I had major corruption at the default factory overclocked speeds but yeah, it would throttle down or hard-lock sometimes as well.

Venturi
04-10-06, 06:37 AM
If I slow down the 7900gtx, the lockups go away. At stock speed they happen after 15 min of play. Slowed down to stable speeds, the 7900gtx unfortunatly, is slower and lathargic compared to the 7800gtx 512 when dealing with resolutions of 2560x1600. Can't win:(

Knot3D
04-10-06, 07:49 AM
Interesting thread !

I see the 7800GTX 512's are a bit available here in NL, but they cost about 150 more than the 7900GTX 512. Strange....