AMD Southern Islands Heads to "London" with the Radeon HD 7900M, 7800M and 7700M GPUs
AMD Takes Radeon HD 7000 Series GCN Architecture Graphics to Notebooks
Now wait a minute. Wasn't the Radeon HD 7000M Series (codenamed London) already available since early this year and HardwareZone has even reviewed a pretty new HP Envy 15 notebook model that featured the Radeon HD 7690M discrete graphics? The answers are yes and yes. Confusing? Certainly, so let us enlighten you on what's really launched today.
Today, AMD has finally unveiled the true next generation Radeon mobile graphics chips using the Southern Islands cores' GCN architecture (28nm process) that first debuted on the desktop based Radeon HD 7000 series GPUs. They will consist of the Radeon HD 7900M, 7800M and 7700M series and will replace the Northern Islands (40nm process) based Radeon HD 6900M, 6800M and 6700M models respectively. As such, you can expect the new GPUs to boast these following features:-
- GCN (Graphics Core Next) Architecture - first featured on desktop Radeon HD 7000 series
- 28nm fabrication process - first featured on desktop Radeon HD 7000 series
- PCIe 3.0 interface - first featured on desktop Radeon HD 7000 series
- AMD Enduro technology - new!
- AMD PowerTune - first featured on desktop Radeon HD 6900 series
- AMD Power Gating and ZeroCore Power - first featured on desktop Radeon HD 7000 series
- AMD App Acceleration (VCE, Steady Video 2.0 and UVD) - first featured on desktop Radeon HD 7000 series
As you can see, most of the highlights of the Southern Islands graphics cores are brought forward to the high-end London Radeon HD 7000M GPUs. What's new are a few extra power management features that have been improved on the new mobile GPUs.
AMD's Power Gating technology helps shut down portions of the GPU during light workloads or even when the screen is static to conserve power while AMD ZeroCore kicks in to power off core portions of the GPU during an extended idle state. The keyword here is "core portions of the GPU", so certain primary elements are still running. However, if the system is configured in CrossFire, ZeroCore steps in to completely shutdown the secondary GPU especially when it's not needed while one is churning some documents and other such non 3D (or gaming) workloads.
AMD's Enduro technology is basically an enhanced edition of switchable technology (to toggle between integrated and discrete graphics such as mentioned here and here), but in a much more updated fashion with better logic to automatically and seamlessly toggle discrete mobile graphics on/off depending on the API calls and workloads. More importantly, AMD Enduro promises that the mobile discrete graphics consumes only 0 watts when powered down in favor of the integrated graphics engine. PowerTune is a pretty cool concept similar to NVIDIA's recently introduced GPU Boost, whereby power sensing technology on the software and hardware are able to determined the power required to run any one application or task and then dynamically throttle the GPU clocks up or down to better utilize the TDP limit of the discrete GPU. This is newly available only on the high-end London series mobile GPUs as it wasn't available in previous mobile Radeon GPUs.
Take note that all of what's mentioned above are applicable only to the new London series which apply to the Radeon HD 7900M, 7800M and 7700M mobile discrete GPUs. The Radeon HD 7000M series launched early this year were targeted at the mainstream and value multimedia notebooks with the Radeon HD 7600M, 7500M and 7450M discrete mobile GPUs. Unlike what many would assume, these GPUs aren't based upon the Southern Islands graphics cores (Radeon HD 7000 series desktop GPUs) - instead, they are still using Northern Islands cores which directly correspond to the existing Radeon HD 6600M, 6500M and 6400M models. So in actual fact, the 7600M, 7500M and 7450M are just rebranded editions of the previous cores but using a newer silicon version that supposedly has slight better power/performance characteristics depending on the final clock speeds and memory used in the actual implementation. This is why when we last tested a Radeon HD 7690M equipped notebook, it didn't feel like next-gen class graphics performance.
Specs Breakdown for Radeon HD 7900M, 7800M and 7700M
From our discussion with AMD, we understand that the top-end Radeon HD 7900M series is targeted at large, heavy-duty gaming notebooks (think Alienware M17 or M18 series), while the Radeon HD 7800M is ideal for mainstream multimedia/gaming grade notebooks. From the specs comparison below, you can tell that the 7900M boasts double the horsepower of the 7800M and that's a pretty big gulf - enough to separate mainstream from pro-gamers. In fact, the Radeon HD 7900M has specs that are quite closely related to the desktop edition Radeon HD 7870!
AMD Radeon HD 7900M series
|AMD Radeon HD 7800M series||AMD Radeon HD 7700M series||ATI Radeon HD 6990M||ATI Radeon HD 6970M||ATI Radeon HD 6870M||ATI Radeon HD 6770M|
|Core Code||Wimbledon||Heathrow||Chelsea||Blackcomb XTX||Blackcomb XT||Granville||Whistler|
|Transistor Count||2800 million||N.A.||N.A.||1700 million||1700 million||1040 million||716 million|
|Core Clock||850MHz||800MHz||675MHz||715MHz||580 to 680MHz||675MHz||675 to 725MHz|
|Stream Processors||1280 Stream processing units||640 Stream processing units||512 Stream processing units||1120 Stream processing units||960 Stream processing units||800 Stream processing units||480 Stream processing units|
|Compute Unit Clusters (GCN)||20||10||8||-||-||-||-|
|Texture Mapping Units (TMU) or Texture Filtering (TF) units||80||40||32||56||48||40||24|
|Raster Operator units (ROP)||32||16||16||32||32||16||8|
|Memory Clock||4800MHz GDDR5||4000MHz GDDR5||4000MHz GDDR5||3600MHz GDDR5||3600MHz GDDR5||4000MHz GDDR5||3200MHz GDDR5|
|DDR Memory Bus||256-bit||128-bit||128-bit||256-bit||256-bit||128-bit||320-bit|
|PCI Express Interface||PCIe ver 3.0 x16||PCIe ver 3.0 x16||PCIe ver 2.1 x16||PCIe ver 2.0 x16||PCIe ver 2.0 x16||PCIe ver 2.0 x16||PCIe ver 2.0 x16|
|Maximum Display Support||Up to 6 via DisplayPort 1.2 MST||Up to 6 via DisplayPort 1.2 MST||Up to 6 via DisplayPort 1.2 MST||Up to 6 via DisplayPort 1.2 MST||Up to 6 via DisplayPort 1.2 MST||-||-|
The Radeon 7800M has specification similar to the desktop Radeon HD 7770 GPU and should make for a decent mainstream gaming companion. The 7700M on the other hand isn't a great deal different from the 7800M and as such, matches up to the specs of a desktop Radeon HD 7750 GPU.
To sum up our similarity comparison of the mobile and desktop variants of the GPUs, here's yet another table:-
|Mobile GPU Model||Equivalent Desktop GPU Class||Suitable Class of Usage|
|AMD Radeon HD 7900M||AMD Radeon HD 7870||Enthusiast Gaming|
|AMD Radeon HD 7800M||AMD Radeon HD 7770||Mainstream Gaming|
|AMD Radeon HD 7700M||AMD Radeon HD 7750||Mainstream Gaming|
Preliminary Performance Expectations
As of now, it seems that only the Radeon HD 7900M series GPUs are going to make a difference to mobile gaming standards seeing that the next in-line 7800M is more or less tied with the 6870M performance levels. Naturally, the 7800M will win the 6870M due to clock speed and architectural enhancements, but it we don't expect it to be a very big margin. That leaves most people wanting to know just what can the 7900M achieve.
Looking back at the performance of the AMD Radeon HD 6970M as tested in the Samsung Series 7 700GA gaming notebook, we've found that it could somewhat rival the very best in industry, which is the NVIDIA GeForce GTX 580M. We've never tested the Radeon HD 6990M, but given the specifications delta from the 6970M, we estimate the 6990M to roughly have 15% more performance than what we experienced with the 6970M.
With the Radeon HD 7970M's vastly better specs, it will undoubtedly set a new record. According to early estimations from AMD, the Radeon HD 7970M is about 50% better than the Radeon HD 6990M. Applying some simple arithmetic, we estimate the Radeon HD 7970M to deliver up to 75% better performance than what we've experience with the Radeon HD 6970M. Referring to the results obtained previously, the Radeon HD 7900M series can effectively tackle high resolution 3D gaming with ease, whereas the previous generation allowed high resolution gaming, but not with adequate smoothness when factoring in 3D as well.
These are just estimations for now, but you can look forward to our future notebook reviews where we'll apply our theories and see if the new generation mobile GPU can really deliver to our expectations. For now we'll leave you with a couple of AMD slides depicting performance advantages, which interestingly only focused on the top SKU only:-