ROPs, Memory Controller

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3:00 AM - 06/25/2008 by Fedy Abi-Chahla, Florian Charpentier

ROPs

ROPs were another weak point of the preceding generation for AMD, given their poor performance with antialiasing enabled. As with the texture units, the engineers started from scratch, again with the goal of maximizing the efficiency of the units per die area.

The first improvement is to Z rendering. ATI had introduced the possibility of doubling the fill rate on depth passes with its preceding architecture, but was still behind Nvidia, which offered a fill rate that was multiplied by eight in these situations. With the RV770, AMD is still behind, only quadrupling the fill rate – to 64 pixels per cycle. Let’s check that with the trusty fill rate tester:

Radeon-HD4850 Geforce-9800-GTX+ GTX-260 GTX-280 Grafikkarten

Again, there is no surprise, as we saw for pure fill rates. On the other hand, Z rendering was a little disappointing. There is some improvement, but where the RV670 came close to its theoretical value (x1.89 instead of x2), the RV770 is far from it (x2.41 instead of x4). That’s just not enough to compete with the G92, which, though it’s also fairly far off the theoretical value (x5.2 instead of x8), is still out of reach.

However, that’s not the main improvement to the ROPs. ATI’s engineers focused on correcting the antialiasing performance, which was catastrophic compared to the competition. And where the RV670 could write only 8 pixels per cycle in MSAA 2X or 4X, with its fill rate divided by two, the RV770 doesn’t take a performance hit, and can still write 16 pixels per cycle in these situations. In the same way, rendering in an FP16 frame buffer has been optimized and is now done at full speed, whereas before the RV670’s fill rate had also been divided by two. Memory controller

Since its introduction of the ring bus with the R520, AMD has continued to work on its memory controller. The latest new feature consists of separating clients that are “bandwidth-greedy” (like the L2 texture cache or the ROPs) from clients that can settle for more reduced bandwidth (the PCI Express controller, the display controller, etc.). Less greedy clients share the same hub, whereas the memory controllers are distributed on the chip near the high bandwidth consumers.

Talkback
Neog2 06/25/2008 11:13 AM
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Wow $200 in Best Buy for a HD 4850,
$450 in Best Buy for a GTX 260.
And the 4850 is pretty close to the 280.

Ouu the 4870 is going to give Nvidia a run for there money
for the first time in a while.

Sarcastic 06/25/2008 11:14 AM
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Good stuff now we just need some 4870 benchies!

Prodromaki 06/25/2008 11:55 AM
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Oced Asus and 4850 instead of 4870 + too many games based on engines favoring nVidia...

P.S. +1000 -> 2222

randomizer 06/25/2008 12:10 PM
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Florian you put a 1920×1077 image on the Crysis page! :lol:

Anonymous 06/25/2008 12:24 PM
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For Mass Effect the Engine limits the Maximum framerate to 62FPS. You can change this in the BIOENGINE.INI file (in the Documents\BioWare\Mass Effect\Config\ folder on Vista) by changing the value:

MaxSmoothedFrameRate=62 in the Engine.GameEngine section

puterpoweruser 06/25/2008 2:18 PM
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I can't believe it took nVidia coming out with a new card again to have tom's make a review finally of the 4850.

"it was unavailable due to the sloppy handling of this launch"
Seriously? AMD can't control if their retail partners screwed the pooch on the release date, because they were so anxious to get people this great product. They made sure the product was readily available well before the launch date.

They should be praised for not having a paper launch, not told that it was a sloppy launch, very poor form saying that.

Hell i went to best buy and bought 2 4850's on sunday, when the cards weren't even supposed to be available yet, the guy told me "they have been in stock for over a month in the back, they aren't supposed to be available yet but i can get two for you." Were the AMD police supposed to come and smack best buy on it's hand and keep me from giving them profits?

Sorry if i'm ranting, just put the blame where it belongs.

Malovane 06/25/2008 2:21 PM
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No offense, Fedy Abi-Chahla and Florian Charpentier, and thanks for the hard work, but I think the article should be revised a bit. First off, this should be a review of graphics cards.. not a burned out overclocked Asus motherboard. If you attribute your 4850 test crashing due to your motherboard.. why throw in results of 0 across the board for the 4850? You just corrupted your data and made the final fps averages meaningless, which is the thing people were generally interested in. Secondly, why in the world are you including tests that don't fit the definition of "playable" on any card in your test lineup (Crysis 2560x1600). It just throws off averages, as people aren't going to run this game at 7fps! If there's no card in the lineup that gets close to 30fps in a certain test, just move on! Save it for the quad crossfire or triple sli tests or something. You're giving high weights to resolutions that only a fraction of a percentage point of dedicated gamers can utilize (and those wouldn't bother with a single GPU). Lastly, please get those annoying gigantonormous screenies out of the review. It makes the review look like it was done by kindergarteners.

puterpoweruser 06/25/2008 2:27 PM
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I didn't finish reading the whole article yet but was the driver hotfix and the current 8.6 driver applied to the 4850?? It improved performance and stability greatly as i saw, it make the actual clock speed the card is set it run nicely and gives it great overhead to overclock through the CCC

draxssab 06/25/2008 2:48 PM
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Who wants the Radeon 4800 full revew? (including the 4870, that do better than the GTX 280 in some games!)

http://www.hardware.fr/articles/72 [...] -4850.html

In french, but the graphs talk by themselves. Ho, and if you want a short translation = impressive and incredibly more efficient than Nvidia (if you compare the size of the GPU, yes it's A LOT more efficient)

spaztic7 06/25/2008 2:58 PM
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These reviews are getting better! Although I have seen many benchmarks and tests of the 4850 before this, I still love seeing how the 48x0 line is doing against the green machine! Anandtech.com has a kill 4870 review!

Haiku214 06/25/2008 3:05 PM
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The downside is the 4850 GPU temp! Makes me rethink about buying one...

GlItCh017 06/25/2008 3:26 PM
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Great read, I've read up on the 4870 on Anandtech as well and it's pretty much the same deal with completely dominating the new Nvidia cards. Performing like a GTX 280 at $100 cheaper. I love the amount of games benchmarked results can vary so much from game to game especially with CF and SLI. Good read!

homerdog 06/25/2008 4:05 PM
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This is quite the turnaround for ATI and we haven't even seen R700 yet. Good times!

dragoncyber 06/25/2008 4:14 PM
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I'm still waiting to see how the 4870X2 scales in crosfire before I make any decisions. My 8800 GT SLI setup is still beating out the GTX280 and scales better than CrossFire currently. Hopefully by the time the 4870X2 comes out ATI will have fixed the drivers and scaled the crossifre better for more games. What we all know is that obviously the 4870x2 will outperform the GTX280, we must then wait and see if Nvidia goes 260X2 or 280X2 to stay on top of the graphics King of the Hill game.

The next couple of months are going to be interesting.

techtre2003 06/25/2008 4:23 PM
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extremetech.com has numbers up for the 4870.

mikeinbc 06/25/2008 4:23 PM
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Absolutely BIAS REVIEW!

The review uses OLD DRIVERS for the ATI cards & gets worse from there.

The drivers used for Nvidia's cards> ForceWare 177.34 beta. Release Date: June 15, 2008
The drivers used for HD4850> Catalyst 8.22 Release Date: July 17, 2006!!!

Sceptrix 06/25/2008 5:06 PM
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Oh I see. Because the motherboard can't run GRID, the 4850 gets a score of zero in graphics tests. That makes perfect sense. After all, anyone using this GPU MUST have the same mobo.

Ogdin 06/25/2008 5:05 PM
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HardwareCanucks has a detailed 4870 review also.

Florian Charpentier 06/25/2008 5:16 PM
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mikeinbc > How can you believe that a 2 year-old driver can support a new generation GPU? The 8.22 beta driver was simply the only driver available that supported the 4850 at the time of review. It is more something like a Catalyst 8.7 beta.

Malovane > Unfortunately we needed to review Crysis in 25*16 in order to be able to calculate the average framerates of each board with each resolution, including the 25*16 that is playable on most games. And to show that no board can currently run Crysis in 25*16.

"If you attribute your 4850 test crashing due to your motherboard.. why throw in results of 0 across the board for the 4850?" > No, I attribute the crashing to the Asus Radeon 4850 TOP that we reviewed.

Florian Charpentier 06/25/2008 5:21 PM
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By the way, as I explained again in the review, I didn't include the 0 score of the 4850 with GRID in the sum-up benchmarks.


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