About Geforce 7 Series architecture

[Julidz]

Why does a 7600GT outperform a 6800GT ?

just someone that wanna learn here


7600GT has 128bits and 12 pipelines while 6800GT has 256bits and 16 pipelines


right , i know that despite 7600's better clocks , there's a more advanced technology in 7 series that makes the 76GT outperforms the 68GT


i just wanna know the details about that , ive heard something about 2 ALUs per pipeline on 76GT versus 1 on 68GT

i would be very grateful of u explain that to me ^^

 

[Techno+]

Link

Look at the link and compare the 2 GPUs. One of the reasons is that each ALU in nvidia's 7 series has a mini-alu to assist it. Although the 7600 GT has fewer pipes than the 6800 GT, it still boasts higher no. of shader operations and better texture fillrate. If i am to take a guess, the bandwidth in the 6800 GT goes wasted, so it is of no use, however, i think the opposite is true when utilizing AA. I really dunno, and don't take my words solid, there are more knowledgeable people around here, so just wait for someone's answer.

 

[digitalwanderer]

Pfft, I was just gonna say it's because the 7600GT is faster.

 

[Julidz]

Link

Look at the link and compare the 2 GPUs. One of the reasons is that each ALU in nvidia's 7 series has a mini-alu to assist it. Although the 7600 GT has fewer pipes than the 6800 GT, it still boasts higher no. of shader operations and better texture fillrate. If i am to take a guess, the bandwidth in the 6800 GT goes wasted, so it is of no use, however, i think the opposite is true when utilizing AA. I really dunno, and don't take my words solid, there are more knowledgeable people around here, so just wait for someone's answer.

but then , could the mini ALU process the same shaders instructions (or have the same shading power) of the "original" ALU ?

 

[Techno+]

but then , could the mini ALU process the same shaders instructions (or have the same shading power) of the "original" ALU ?

I need to have a look at the B3d article about the G70 to answer this but i cant find it.

 

[Davros]

in case your interested the benchmark program that comes with f1 challenge rates the
6800gt at 90.2 mtri/sec
7600gt at 97.8 mtri/sec

 

[JoshMST]

From my understanding is that there are multiple reasons.

First and formost is the number of units at work and the clockspeed they are working at. 6800 GT was 16 ROPS/Tex/Shaders at 350 MHz while the 7600 GT is 8 ROPS, 12 shaders/Tex at 560 MHz. Overall pixel fillrate of the 7600 GT is slightly lower, but when combined with slightly better shader units clocked significantly higher, you can see where most of the performance comes from.

In high res + AA scenarios, the 6800 GT does better, but is still behind for the most part. Part of that is the 2 megapixel limitation of the overdraw/fast clear/etc. unit. Anything over 2 megapixels causes a large performance hit because those bandwidth and work saving mechanisms just won't work. For the 7 series it was upped to 3 megapixels I believe.

Lots of other architectural tweaks have helped the 7600 GT overcome the 6800 GT.

 

[AnarchX]

Another reason is, that it has only 12 PP @ the high clock of 565MHz, so the stall problem of GF6/7-series is much lower in this configuration than on 6800GT.

 

[Julidz]

Thank you guys

I think I posted in the wrong session , I really wanna know the details about G7series architecture like the function of these mini-ALUs


so Im going to create a topic in 3D Technology & Architecture



Thx again

 

[Julidz]

I know at this stage this is out of date , but here's someone who wanna learn a bit


here we go :


the question is...why does a 7600GT outperform a 6800GT ?

7600GT has 12 pixelpipelines and it's 128bits while 6800GT has 16 pixelpipelines and it's 256bits

despite of the higher 7600's clock speed , there's a better "pipeline" architecture that makes 7600GT have more shader muscle , right ?

I've heard something about an ALU and mini-ALU per pixel shader unit that would provide this shader muscle

so , how is that ?


thx

 

[Kaotik]

I think you should take a look to for example Beyond3D's reviews on the cards you're referring, they should explain it quite well, the biggest reason is as far as I know indeed better ALU's in G7x

 

[Zaphod]

Post redundant after thread merge.

 

[Julidz]

One thing to learn is not to post two threads with the exact same question five days apart when you have already gotten some good answers in the first one. Although, the original thread was in the wrong forum, it is better to ask a mod to move the first thread than to repost the question. :smile:

atually , I didn't get what I really want there and dind't know that it's possible to to ask a mod to move the other topic to this session

so maybe is it possible to close the older thread in the wrong session ?

I think you should take a look to for example Beyond3D's reviews on the cards you're referring, they should explain it quite well, the biggest reason is as far as I know indeed better ALU's in G7x

i didn't find any B3D's aricle or review about G70 :/

 

[Rufus]

i didn't find any B3D's aricle or review about G70 :/

Sadly when they updated the website a few months ago, a lot of the older content never got updated to the new site. If you look through the article and review list you'll see there's a lot of content missing, including the G70 article/review. I don't know if/when they're going to pull in the archives.

 

[Tim Murray]

Sadly when they updated the website a few months ago, a lot of the older content never got updated to the new site. If you look through the article and review list you'll see there's a lot of content missing, including the G70 article/review. I don't know if/when they're going to pull in the archives.

we're working on it. by we, I mean Geo, because the rest of us suck and he is a prince among men.

 

[Nick]

7600GT has 12 pixelpipelines and it's 128bits while 6800GT has 16 pixelpipelines and it's 256bits

12 pipelines x 560 MHz = 6720
16 pipelines x 350 MHz = 5600

Add to that the mini-ALU's and it's clear the 7600 wins in shader power hands down.

128-bit x 1.4 GHz = 179.2
256-bit x 1.0 GHz = 256.0

Here the 7600 has a disadvantage. However, G7x likely has larger texture caches, which reduce bandwidth needs somewhat. In bandwidth limited applications the 6800 still won though as far as I can remember.

 

[Geo]

we're working on it. by we, I mean Geo, because the rest of us suck and he is a prince among men.

I'll be happy to name you a duke among men anytime you want to help!

But any rate, Tim's right. It's not gone forever, it's just coming back slowly. Interviews are back fully. Articles are coming back bit by bit, more every week. Then we'll turn to the rest of the reviews/previews from the old site. Tho we've gotten a representative sample of some major milestones there already.

 

[Julidz]

12 pipelines x 560 MHz = 6720
16 pipelines x 350 MHz = 5600

Add to that the mini-ALU's and it's clear the 7600 wins in shader power hands down.

128-bit x 1.4 GHz = 179.2
256-bit x 1.0 GHz = 256.0

Here the 7600 has a disadvantage. However, G7x likely has larger texture caches, which reduce bandwidth needs somewhat. In bandwidth limited applications the 6800 still won though as far as I can remember.

hmm right

but actually both (G6 and G7) have one primary ALU and one secondary ALU per pixelpipeline

the main point is that both 7600's pixelpipeline ALUs can do MADD operations but also one of them shares shading operations with texture operations and so doesn't have the same shading power , right ?

on the other hand , 6800 pixelpipelines have 1 ALU that can do MADD ops but the secondary can only do MUL ops and also shares shading power with texture power , true ?

so , that's lot of more shading power to 7600GT and would it be the main reason to outperform the 68GT ?

 

[fellix]

The main difference between pixel pipes of both GPUs, is the dual-MADD capability of the G70, where the TEX bounded primary ALU is now a full functional copy of the second one, so in theory (with co-issuing), a G70 pipe can process more shader op's in a row, if we don't take into account the texture fetching stalling.
The other thing relating the pixel processing is that for each pixel quad, G70 have a local program counter, where for NV40 the entire array of pixel pipes is viewed as a single giant SIMD unit with its excessive 4K fragments-in-flight large batch size (for the 16-pipe chips).

 

[Davros]

i just wondered how come the 6800 is clocked so low compared to the 7600 ?
escpecially as the heatsink on my 7600 is a little puny thing while on my 6800 it was a full length dual slot copper monster