ATI Radeon HD 4850 Linux Performance
While the ATI Radeon HD 4800 series was greeted with same-day Linux support, this first-cut Linux support clearly isn't as well optimized as the Windows driver. Alternatively, to this point they may have spent all of their resources tuning the DirectX performance and have forgone tuning the OpenGL side. Benchmarks we were provided back at the NDA launch event for the Radeon HD 4800 series last week show the Radeon HD 4850 outperforming the NVIDIA competition with Microsoft Windows Vista. Test results from Windows-based publications have concurred with these metrics provided by AMD. It isn't by a small margin either, but AMD's press literature characterizes the Radeon HD 4850 as being 55% faster than the NVIDIA GeForce 8800GT and performing significantly faster than the GeForce 9800GTX.
As you have witnessed already from the results, in a number of the tests the Radeon HD 4850 had fell behind the GeForce 8800GT and 9800GTX. In fact, the Radeon HD 4850 hasn't shown to be much faster than the Radeon HD 3870 on Linux. In Nexuiz, OpenArena, Doom 3, Quake 4, and X-Plane, the Radeon HD 4850 had fallen noticeably behind the NVIDIA competition. In Enemy Territory: Quake Wars and GtkPerf, however, the Radeon HD 4850 had risen to the top. In Enemy Territory: Quake Wars at 1920 x 1200 with high quality settings, the Radeon HD 4850 was about 8% faster than the GeForce 9800GTX. In the 2D GTK tests, the Radeon HD 4850 was dramatically faster than the GeForce 8800GT and 9800GTX. However, NVIDIA has known problems with 2D Linux performance. For the record, when the GeForce 8 series was introduced it initially had a major performance delta too between Windows and Linux.
What's the explanation for the Radeon HD 4850 on Linux falling so far behind their competitors? According to AMD engineers the Linux driver has yet to be well optimized. Our Enemy Territory: Quake Wars results were what they had expected, but within Doom 3 and Quake 4 in particular, it's likely being limited within the driver. Down the road we may (likely) see optimizations in later Catalyst releases that will address these performance shortcomings.
An overwhelming majority (if not all) of the Windows reviews on the ATI Radeon HD 4850 are very much in favor of this graphics card. The Radeon HD 4850 sells for under $200 USD and it's able to blow away the competition. The Radeon HD 4870 has also received very favorable reviews with it going head-to-head against the GeForce GTX 260. On Linux though we're only able to see the Radeon HD 4850 shine in Enemy Territory: Quake Wars for OpenGL performance and even there it isn't pulling much of a lead over the Radeon HD 3870 (Windows benchmarks have shown the Radeon HD 4850 being faster than even the Radeon HD 3870 X2 dual-GPU part). In Doom 3 and Quake 4 the Radeon HD 4850 is about 20% slower than the GeForce 9800GTX!
It's certainly tough to judge a graphics card that has received many accolades on Windows but on Linux it's currently running significantly slower in these OpenGL tests. The good news is that with much of the code-base now being shared between the Windows and Linux drivers, the optimizations that go into the OpenGL portion of the driver will hopefully shine through on the Linux side. About a 20% performance boost is needed within the Linux driver in order to bring it properly up to speed. Are we confident that this can be achieved? If it was a year ago and prior to AMD rolling out their new OpenGL driver, this wouldn't be possible, but we're now fairly confident that AMD will be able to deliver the needed performance optimizations in future driver releases.
AMD is also quickly ascending to a feature parity between the Windows and Linux Catalyst suites. As we shared last week, CrossFire is coming to Linux next quarter. Once there is the CrossFire support available or we are allowed to share early Linux benchmarks of it, we will have a full run-down on it with the Radeon HD 4800 series. Aside from CrossFire, their Linux software team is working on several other interesting features for the driver to be introduced in the near future. We will have a full run-down on those features when they arrive.
If you are a Linux user but dual-boot into Windows to play many of your games, by all means the Radeon HD 4850 is a great graphics card for you. This graphics card -- which is the first to break the TeraFLOP barrier -- sells for less than $200 USD and it's been shown to deliver excellent performance on Windows. On Linux though, the GeForce 9800GTX, which is now similarly priced to this RV770 GPU, is the performance champion in all but Enemy Territory: Quake Wars and the 2D testing. This should, however, change with future Catalyst updates when this driver bottleneck is addressed.
If you care at all about open-source support for discrete graphics cards, get the ATI Radeon HD 4850. The Radeon HD 4850 already works with the xf86-video-ati driver and will be supported by xf86-video-radeonhd with due time. Later this year we should hopefully see open-source 2D, 3D, and video playback arrive for the RV770 graphics processor (along with NDA-free programming documentation for this ASIC).
Two of the other factors to consider about the RV770 is their lead in performance-per-watt and GPGPU support. The ATI Radeon HD 4850 has greater power efficiency over earlier Radeon products and the NVIDIA GeForce 9800GTX. On the GPGPU side, the TeraScale Graphics Engine with 10 SIMD cores should be a huge winner if you're interested in doing any Stream (CAL/Brook+) work on Linux (see AMD Releases Stream SDK For Linux and AMD Talks About Stream SDK On Linux).
The bottom line right now is there are a few troubles with the Catalyst 8.6 for Linux and the Radeon HD 4850. If you don't need to make a graphics card decision immediately, stay tuned to Phoronix with our display driver articles and graphics card reviews and you will be able to stay up-to-date on the absolute latest information going on within the ATI Linux camp. In the coming days we'll also be looking at the ATI Radeon HD 4870 and sharing our initial Linux benchmarks for that flagship graphics card. Certainly though this is a much better boat to be in where we now have same-day hardware support on Linux, where with the Radeon X1000 and Radeon HD 2000 generations we had to wait over six months each time for any level of support.
For other reviews and pricing on the ATI Radeon HD 4850, visit TestFreaks.com.
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