There has already been a couple topics and several posts that talk about and argue the merits of the new macs, this thread aims to give the people who jump into this forum the facts as well as some comparisons. It's intended as a quick reference of information for those who are considering purchasing the new iMac ("Mid 2007"), and need technical details about the GPU to help their decision. To start things off, let's get a few details out of the way. iMacs are essentially "desktop laptops", they use mobile processors, mobile ram, and they also use mobile GPUs. This is not specifically advertised. Because of this, keep in mind any time the GPUs are talked about in the specifications, they are actually the "Mobility" (ATI) or "Go/M" (nVidia) series graphics cards. If you want to play games the best thing to do in an iMac is to add more memory (RAM), stock 1GB tends to be a bottleneck and will prevent the rest of the system from reaching its full potential. The HD 2400 XT is less powerful then the "plain" HD 2400 Yes, the HD 2600 Pro (Mobility) in the new iMacs is the best GPU offered in an iMac to date (that's right, better then the X1600 and the 7300GT) The HD 2X00 Series cards have a completely different architecture that few games are taking advantage of right now. It's designed to be shader intensive - In fact they can easily offer double the shader operations of the nVidia 8 Series cards! (8600GT, etc). This will be more of a payoff in newer shader-heavy games/engines then current gen games. They are also very new cards - and as with any brand new GPU expect major performance improvements with more optimized drivers. Developers likely haven't even had much time with them yet, so look at benchmarks distrustingly for now, performance is almost garaunteed to improve as both drivers and game software matures. Okay, on to some specs and comparisons. The first comparison here will not be of the "Mobility" class since I can't find a good site that includes the mobile version of the HD 2X00 series cards (they are too new). GPUReview.com - ATI HD 2600 Pro VS X1600 Pro (You can change the cards to view different comparisons, hopefully the site will update with the mobile versions of the new cards soon.) One thing you should notice immediately from that comparison is the the HD 2600 has a HUGE boost in Shader Operations from 72,000 vs 6,000. It's worth noting, though, that the X1600 has a separate Vertex unit, so those numbers aren't a direct 1:1 ratio. For more details on shader operations, see: GPUReview.com - Shader Operations Here's a notable snipped: So what games are shader-heavy? I'm not sure about current games, especially as a lot of this is still classed as "DirectX 10" and "Shader Model 4.0", which no games out (to my knowledge) support this. My best guess, would be newer games: Crysis, RAGE, UT3, etc. Specifically, anything that will be running on CryENGINE 2 (Crysis), iD Tech 5 (RAGE), and Unreal Engine 3 (UT3, Gears of War) That being said, the GPUs in iMacs aren't (and will never be), high-end cards. These aren't HD 2900s or 8800 GTXs, don't expect to max out resolution and settings. ---------- Now, here's some technical details on the cards in question (I'll list the Mobility HD 2600 Pro, then only list notable performance number differences for the other cards): ATI Mobility Radeon HD 2600 - Overview ATI Avivo HD High Definition video playback, including full HD DVD and Blu-ray disc support while on battery "Radically New" and Efficient 3D Architecture Performance-per-Watt (Requires only 45W) ATI Mobility Radeon HD 2600 - Specifications Features 390 million transistors using 65nm fabrication process (Should run cooler then 90nm) Unified superscalar shader architecture 128-bit 4-channel GDDR3 memory interface 256-bit internal ring bus for memory read/write Unified Superscalar Shader Architecture 120 stream processing units (Dynamically balance for vertex/geometry/pixel shaders) 128-bit floating point precision for all operations Command processor for reduced CPU overhead Up to 40 texture fetches per clock cycle Up to 128 textures per pixel High-resolution texture support (up to 8192 x 8192) 8 render targets (MRTs) with ant-aliasing support Physics processing support Full support for Microsoft DirectX 10.0 Shader Model 4.0 Geometry Shaders etc Anti-aliasing features Multi-sample anti-aliasing (up to 8 samples per pixel) Custom Filter Anti-Aliasing (CFAA) for improved quality Adaptive super-sampling and multi-sampling All anti-aliasing features compatible with HDR rendering Texture filtering features 2x/4x/8x/16x high quality adaptive anisotropic filtering modes (Up to 128 taps per pixel) 128-bit floating point HDR texture filtering Shared exponent HDR (RGBE 9:9:9:5) texture format support ATI Mobility Radeon HD 2400 XT - Specifications Features 180 million transistors using 65nm fabrication process 64-bit single channel GDDR3 memory interface Unified Superscalar Shader Architecture 40 stream processing units Up to 16 texture fetches per clock cycle Anti-aliasing features Multi-sample anti-aliasing (up to 4 samples per pixel) ATI Mobility Radeon X1600 - Specifications Features 157 million transistors using 90nm fabrication process 128-bit 4-channel GDDR3 memory interface Ultra-Threaded Shader Engine DirectX 9.0 Shader Model 3.0 12 pixel shaders 5 vertex shaders The standout in these specs to me, personally, is that the Mobility HD 2400 XT has such a drastically slower memory interface! A single channel 64-bit interface compared to 4-channel 128-bit interfaces. On the surface it looks like everything else might beat out the X1600 found in older iMacs, but it seems highly likely the memory interface will strangle the card from ever outperforming it, though. Time will tell, I suppose.