ATI Radeon HD 4850: Smarter by Design?

ROPs, Memory Controller


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.

  • Neog2
    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
    Good stuff now we just need some 4870 benchies!
  • Prodromaki
    Oced Asus and 4850 instead of 4870 + too many games based on engines favoring nVidia...

    P.S. +1000 -> 2222
  • randomizer
    Florian you put a 1920×1077 image on the Crysis page! :lol:
  • 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
    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
    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
    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
    Who wants the Radeon 4800 full revew? (including the 4870, that do better than the GTX 280 in some games!)

    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
    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! has a kill 4870 review!