From Fixed-Function to Unified Shaders

In the summer of 2007, ATI unveiled the RV600 series, known as the Radeon HD 2000 series.

These new GPUs were built on a new architecture called TeraScale 1 and marked a radical shift in GPU design, moving away from previous generations’ fixed-function pipelines which could be found on all cards back to the very first 3d accelerators.

Individual vertex and pixel shaders were replaced by a unified shader model in which a pool of stream processors could handle vertex, pixel, and geometry shading interchangeably.

This series of graphics cards was not ATi’s first foray into the world of unified shaders as they had experience developing the chip contained within the Xbox 360 Console, with a GPU called Xenos.

The RV600 series directly competed with Nvidia’s G80 architecture from the GeForce 8 series which also utilised unified shaders and was released half a year earlier in November 2006.

• ATI TeraScale/HD2000: Implemented fewer, but wider SIMD shader units. Each ATI “stream processor” was highly efficient, able to parallelize workloads better for certain compute tasks, meaning ATI cards often delivered higher performance-per-watt than their Nvidia rivals of the time. For example, the HD 2600 variants had 120 stream processors; the HD 2900 XT had 320. The architecture’s ability to assign any shader processor to any task, and its optimizations for efficiency, sometimes resulted in superior performance in shader-heavy applications despite lower raw hardware counts.
• Nvidia Tesla/G80: Focused on having more individual shader units, but each was less wide and specialized than ATI’s. This approach led to higher raw peak throughput but could result in lower efficiency under real-world loads, especially those requiring extensive parallelism. Nvidia’s design sometimes excelled in brute-force scenarios but could lag in efficiency per shader, particularly in DirectX 10 titles at the time.

With codenames like RV610, RV630, and R600, the HD2000 series spanned three performance tiers:

• RV610 (HD 2400): Designed for budget systems, featuring efficient power use and enhanced media playback through its on-die Unified Video Decoder (UVD).
• RV630 (HD 2600): Struck a balance between gaming and multimedia, incorporating both performance and tuning for video decoding.
• R600 (HD 2900): The flagship, built for raw power, equipped with a massive 512-bit memory bus and workstation-class ambitions, though it notably omitted dedicated hardware UVD.

Despite impressive specs, especially on the HD 2900 XT, the generation was a mixed bag for enthusiasts.

Driver immaturity and lack of hardware video decode (in the high-end model) tempered excitement in early months.

It was completely packed full of dust on arrival so I stripped it down, cleared it out and repasted it which is always a satisfying experience.

It worked flawlessly though, no issues at all with installation and setup. I downloaded the latest driver from the AMD website – Catalyst 13.4 (13.9 for the Win7 testing later). I used DDU to clear out the older driver in safe mode, easily done once you find a version that works in XP (for me that is version 17.0.8.6).

As you can see from the connector at the top, this card is CrossFire capable also so I’m keeping my eye out for another to run alongside it in the same system.

The short table of HD2000 series cards is below, this Sapphire card is highlighted along with the Lenovo version previously tested and reference figures after.

Looks-wise, the Sapphire card is great. I love Sapphire cards from this era—they’re always among the best-looking ATI options, and this one is no exception:

Here’s a table showing the HD2000 family and where this Sapphire card appears:

Here’s GPU’z screenshot of this Sapphire Card:

Game Overview:

Tom Clancy’s Splinter Cell launched on November 19, 2002, developed by Ubi Soft Montreal. Built on the LithTech Jupiter engine (Unreal Engine precursor), it pioneered tactical stealth gameplay with groundbreaking light/shadow mechanics and realistic audio design. The game set new standards for immersion through dynamic lighting where visibility literally shaped gameplay.

Known for its revolutionary light-based stealth, Splinter Cell remains the ultimate benchmark for early 2000s GPUs. The game’s real-time shadows, particle effects, and high-poly environments brutally stress fillrate and shader performance even on modern retro hardware.

I have the GOG version of the game which has an internal benchmark that can be used.

Performance Notes:

In this title, with Max settings, the game becomes CPU limited in the 170fps range.

1024×768 is where the HD2600XT ramps up to full capacity and it posts a very handy 142 average FPS across all maps.

At a higher 1280×1024, the FPS drops to 95 fps, still very playable, matching the previous generation mid-range 7600GT from Nvidia.

Game Overview:
Released in October 2002, Unreal Tournament 2003 was built on the early version of Unreal Engine 2. It was a big leap forward from the original UT, with improved visuals, ragdoll physics, and faster-paced gameplay.

The engine used DirectX 8.1 and introduced support for pixel shaders, dynamic lighting, and high-res textures all of which made it a solid test title for early 2000s hardware.

We played a lot of this and 2004 at LAN parties back in the day.

Still a great game and well worth going back to, even if you’re mostly limited to bot matches these days. There’s even a single-player campaign of sorts, though it’s really just a ladder of bot battles.

The game holds up visually and mechanically, and it’s a good one to throw into the testing suite for older cards. The uncapped frames are pretty useful for my purposes.

Performance Notes:
This mid-range card from 2007 has absolutely no problem running UT2003.
Average framerate lands comfortably in the triple figures, even with effects and detail settings pushed up. Gameplay is smooth, responsive, and visually sharp, no stutters, no complaints.
It’s not a stress test for the HD2600XT, but it’s a good compatibility check and a fun one to revisit.

The test does seem to favour the older fixed-function cards, the 7600GT demonstrating that this isn’t a simple ATI vs Nvidia thing.

Game Overview:

Released for Windows in December 2003, with later ports to Mac OS X and Linux, X2: The Threat is a space trading and combat simulation developed by Egosoft. It continues the story from X: Beyond the Frontier, placing players in the role of Julian Gardna, a former pirate drawn into a conflict with a new alien threat known as the Khaak

While not tied to a widely licensed engine like Unreal, X2 introduced a new in‑house graphics engine built specifically for the X‑Universe. This engine delivered Improved ship and station models, More detailed sectors with nebulae and environmental effects, Dynamic lighting and particle effects and Support for DirectX 8.1‑class hardware, aligning it with early‑2000s GPU capabilities.

This made X2 a solid benchmark title for PCs of the era, especially for players testing mid‑range and high‑end GPUs from the GeForce 3/4 and Radeon 8500/9000 families.

This is the GOG version again and it does have an internal benchmark.

Performance Notes:

This old title clearly prefers fixed-function pipelines and cannot utilise the unified shaders of the HD2600XT effectively. Even the 6600GT performs much better than our HD2600XT here.

Game Overview:
Released in August 2004, Doom 3 was built on id Tech 4 and took the series in a darker, slower direction. It’s more horror than run-and-gun, with tight corridors, dynamic shadows, and a heavy focus on atmosphere. The engine introduced unified lighting and per-pixel effects, which made it a demanding title for its time, and still a good one to test mid-2000s hardware.

Game Overview:
Far Cry launched in March 2004, developed by Crytek and built on the original CryEngine. It was a technical marvel at the time, with massive outdoor environments, dynamic lighting, and advanced AI. The game leaned heavily on pixel shaders and draw distance, making it a solid stress test for mid-2000s GPUs. It also laid the groundwork for what would later become the Crysis legacy.

The HD2600XT is more than capable of pushing huge framerates with the minimum quality option, there is no need to drop things this far.

Things are mainly CPU limited until 1280×1024.

This Sapphire card does edge out the Lenovo by a 17fps, both fall short of the 8600GT and the previous generation 7600GT.

At Ultra quality settings, 4X AF but leaving off Anti-Aliasing, the HD2600XT still performs well. Even at 1280×1024 it exceeds 60fps. Still well behind the 8600GT.

At 1280×1024 the pack loosens up and you can clearly see the advantages that the earlier fixed-function cards have over these early unified shader cards.

Anti-aliasing is not kind to the ATI cards; even the 6600GT beats the HD2600XT, not a great showing.

Arguably playable at 1024×768 but still.

Game Overview:
F.E.A.R. (First Encounter Assault Recon) launched on October 17, 2005 for Windows, developed by Monolith Productions. Built on the LithTech Jupiter EX engine, it was a technical showcase for dynamic lighting, volumetric effects, and intelligent enemy AI. The game blended tactical shooting with psychological horror, earning acclaim for its eerie atmosphere and cinematic combat.

Performance Notes:

The HD2600XTs perform uniformly well at 1024×768 without AA included, this at Max settings but without AA.

They are beaten by both the 7600GT and 8600GT however, and we can’t blame the older game favouring fixed pipelines as the unified shader 8600GT is well ahead.

With Anti-Aliasing though the HD2600XT performance plummets down, close to half of the performance of the 8600GT.

The minimum framerate is also very low in comparison to the average FPS, so this is not expected to be a smooth experience in game.

Game Overview:
Battlefield 2 launched on June 21, 2005, developed by DICE and published by EA. It was a major evolution for the franchise, introducing modern warfare, class-based combat, and large-scale multiplayer battles with up to 64 players. Built on the Refractor 2 engine, it featured dynamic lighting, physics-based ragdolls, and destructible environments that pushed mid-2000s hardware.

No single-player campaign, but I find bot matches via Instant Action a lot of fun. It was hugely popular in its day, especially for Commander Mode, vehicle combat, and it apparently had a thriving modding scene.

Performance Notes:

The HD2600XT performs well in this title and doesn’t fall too far behind the 8600GT. It actually comes in slightly ahead of the 7600GT so doing better here than we are getting used to.

That is until AA is enabled and it all falls down again, 52fps compared to the 84fps of the 8600GT. The Average FPS is actually slightly better than the Nvidia card, but hardly a victory.

Game Overview:

Need for Speed: Carbon launched on October 30, 2006 in North America, developed by EA Black Box and published by Electronic Arts. It continued the series’ street-racing focus after Most Wanted but shifted the action to canyon showdowns and crew-based racing, adding stronger emphasis on territory control and team support. The game was built on the EAGL engine and designed to showcase glossy car models, night-time city lighting, and heavy visual effects suited to mid-2000s gaming PCs and consoles.

Performance Notes:

Interesting results in this title, the HD2600XT performs very well and beats the 8600GT quite handily with the medium preset

moving up to Max settings and things are slowing down for all tested cards, the HD2600XT still has the edge over the 8600GT though and the 7600GT is trailing.

… and a familiar story when AA is enabled. Both the 7600GT and 8600GT take the lead by a large margin – over 100% faster in the case of the 8600GT

Game Overview:
Released on November 10, 2006, Medieval II: Total War was developed by Creative Assembly and published by Sega. It’s the fourth entry in the Total War series, built on the enhanced Total War engine with support for Shader Model 2.0 and 3.0. The game blends turn-based strategy with real-time battles, set during the High Middle Ages, and includes historical scenarios like Agincourt.

Game Overview:

Test Drive Unlimited launched in 2006, developed by Eden Games and published by Atari. It took the series in a new direction with a huge open-world recreation of Oahu, where driving, buying cars and homes, and challenging other players were all part of the experience.

It was built on Eden’s Twilight 2 engine, giving it a more ambitious open-world setup than the previous Test Drive games. The big hook was its “massively open online racing” style, which blended solo progression with always-on multiplayer roaming.

Performance Notes:

In the battle between HD2600XT and 8600GT the Nvidia card seems to have the edge but a little on average FPS and a whole lot on the 1% lows – so a smoother experience with the 860GT.

The fixed function cards start to fall down the rankings in this title which is interesting, even two 7600GTs working together fall well below the HD2600XTs.

That is, of course, until the Anti-Aliasing switch is toggled, dropping the average FPS from 57 right down to 27.

The results scale at 1280×1024, forget this resolution if you have the HD2600XT, the performance payoff, even without AA are too pronounced.

Game Overview:
Oblivion launched on March 20, 2006, developed by Bethesda Game Studios. Built on the Gamebryo engine, it introduced a vast open world, dynamic weather, and real-time lighting. The game was a technical leap for RPGs, with detailed environments and extensive mod support that kept it alive well beyond its release window (it’s just had a re-release recently).

Known for its sprawling world Oblivion remains a benchmark title for mid-2000s hardware. The game’s reliance on draw distance and lighting effects makes GPUs struggle.

Performance Notes: Running at 800×600, the Sapphire HD2600XT is now firmly in last place. Not by a huge margin, but enough to notice. The 8600GT holds up better, especially when Anti-Aliasing is switched on — and it really does make a difference in this game. The visuals sharpen up nicely, and the framerate stays respectable.

More strange results for the Sapphire Card but it does not perform well, the Lenovo card getting the upper hand with it’s 512Mb of VRAM

Conclusion:
The HD2600’s are unable to keep up with the 8600GT but still give playable performance.

Game Overview:
Crysis launched in November 2007 and quickly became the go-to benchmark title for PC gamers. Built on CryEngine 2, it pushed hardware to the limit with massive draw distances, dynamic lighting, destructible environments, and full DirectX 10 support.

The game is just about playable on the HD2600XT and 8600GT under DirectX 9.
‘Very High’ settings are technically selectable, but not on XP. To be tested separately later in the article.

Performance Notes:

At 1024×768 Low settings the game is playable on the HD2600XT with an average framerate of 57fps.

The Lenovo card has the edge, the extra VRAM must be helping its cause.

Both cards beat the 8600GT by a noticeable margin, though suffer worse 1% lows.

The medium preset performance suffers hugely, close to half the framerate and the 8600GT takes the lead over the Sapphire card, though the Lenovo card remains on top.

At the high preset, at the same resolution the game becomes unplayable on all cards, 17fps for the sapphire card matches the 8600GT.

Performance Notes:
Medium settings under DirectX 9 hit the frame cap easily and deliver smooth gameplay.

Vsync was disabled, but the engine still seems to limit frames to what the monitor can handle, despite the switch being toggled off.

Switching to Maximum settings nudges the AA slider up a notch. Still playable, though not as smooth.

Enabling Dynamic Lighting is where things fall apart, framerate drops to around 27 FPS, and it’s noticeable.

The game remains playable at high settings if you avoid Dynamic Lighting, but it’s clear the HD2600XT is working hard to keep up.

Game Overview:
Assassin’s Creed launched in November 2007, developed by Ubisoft Montreal and built on the Anvil engine. It introduced open-world stealth gameplay, parkour movement, and historical settings wrapped in sci-fi framing. The first entry takes place during the Third Crusade, with cities like Damascus, Acre, and Jerusalem rendered in impressive detail for the time.

Performance Notes:
A tough game for most GPUs, but the HD2600XT does a respectable job keeping the frames flowing at medium settings.

There are no presets as such, just menu options you can tweak in-engine. No restart required, thankfully. I hate games that make you reboot just to change a texture slider.

49 FPS average at 1204×768 with detail on high feels good to play and probably what I’d recommend.

In this later benchmark the HD2600XT is actually only a small amount below the Nvidia competition, but still behind nonetheless.

The Sapphire HD2600XT Runs cool and quiet at stock settings, 44% of fan speed at full load keeps things under 62 degrees.

The card has a 45w TDP and the total system draw from the wall sticks at a steady 170w.