AMD's 2012 Mobile Strategy Revealed: Trinity Becomes Fusion

The following table will give an overview over the different models launched for notebooks including the 25W quad-core and 17W dual-core. We will cover the detailed specs of the different GPUs in a separate table later.

Model	Clock (Turbo)	Cores	L2 Cache	GFX	TDP
A10-4600M	2.3 (3.2) GHz	4	4 MB	HD 7660G	35W
A8-4500M	1.9 (2.9) GHz	4	4 MB	HD 7640G	35W
A6-4400M	2.7 (3.2) GHz	2	1 MB	HD 7520G	35W
A10-4655M	2.0 (2.8) GHz	4	4 MB	HD 7620G	25W
A6-4455M	2.1 (2.6) GHz	2	2 MB	HD 7500G	17W

The GPU part of Trinity is much more exiting, even though it consists of already known technology. Concretely, the GPU features the VLIW4 architecture, which was previously used only in the high-end discrete GPU segment for Radeon HD 6900 series cards. Before the APUs will transition to AMDs current GCN architecture, it gives VLIW4 a second opportunity to shine. VLIW4 was specifically designed to provide more efficient utilization of resources compared to the VLIW5 architecture found in Llano as well as Radeon HD 5000 series as well as some 6000 series (excluding 69x0) and even some Radeon 7000 series OEM products that are simply relabeled old products. AMD specifically touts improved performance per mm² of silicon space. We believe that this helped offset some of the deficiencies of the Bulldozer design approach criticized in an earlier paragraph.


Trinity's 3D engine is one of parts how Trinity got its name: Piledriver CPU + Northern Islands GPU + Southern Islands Video

Compared to the Radeon HD 6900 series GPUs codenamed Cayman, the GPU in Trinity is much smaller of course. AMD specifies it to have up to 384 stream processors. This is a bit less than in Llano, but due to higher clock speeds Trinity packs more punch. While the Llano GPU topped out at 600 MHz, Trinity raises the clock up to 800 MHz. Due to the different internal architecture of the units comprising the GPU, in Trinity there are more texture units improving texel fill rate. The amount of ROPs has stayed the same and thus pixel fill rate will only scale with clock speed.

The following table gives an overview of the different bins that are used in the mobile Trinity models. For comparison purposes, the specs of the HD 6620G found in the Llano-based A8-3500M are included. The GFLOP figures are not comparable to AMDs marketing, as AMD includes the FP performance of the CPU part as well.

	6620G	7660G	7640G	7520G	7620G	7500G
Architecture	VLIW5	VLIW4	VLIW4	VLIW4	VLIW4	VLIW4
Clock	444 MHz	497 MHz	497 MHz	497 MHz	360 MHz	327 MHz
Turbo Clock	-	686 MHz	655 MHz	686 MHz	497 MHz	424 MHz
Shader Units	400 (80 x5)	384 (96 x4)	256 (64 x4)	192 (48 x4)	384 (96 x4)	256 (64 x4)
GFLOPs	355.2	381.7 (526.8)	254.5 (335.4)	190.8 (263.4)	276.5 (381.7)	167.4 (217.1)
ROPs	8	8	8?	4?	8	8?
Pixel Fillrate	3.55 GPix/s	3.98 (5.49) GPix/s	3.98 (5.24) GPix/s	1.99 (2.74) GPix/s	2.88 (3.98) GPix/s	2.62 (3.39) GPix/s
Texture Units	20	24	16	12	24	16
Texel Fillrate	8.88 GTex/s	11.93 (16.46) GTex/s	7.95 (10.48) GTex/s	5.96 (8.23) GTex/s	8.64 (11.93) GTex/s	5.23 (6.78) GTex/s

Similar to Llano there will also be lower SKUs with a smaller amount of shader processors and texture units as well as ROPs. Leaked information point to additional SKUs with only 128 shader processors, but for now this is everything AMD launched. The number of texture units is the shader count divided by 16, while the number of ROPs will probably be 4 for some of the lower end models similar to Llano. The ROP number is market with a question mark where we weren't 100% at press time whether it's the correct number. We are fairly sure the 192 shader version (and below) will only come with 4 ROPs and the 256 shader version will retain all 8 units but this is only an educated guess.

The way the GPU accesses memory seems to be the same as with Llano. The memory controller is organized in two unganged 64-bit controllers that can independently handle requests when there are accesses for both the CPU and GPU to be served. The GPU gets a fixed amount of memory that is dedicated to it, which can be configured at the BIOS level. Some notebooks might not allow the user to change the amount though. There are now also memory p-states, meaning the frequency will be dropped as soon as the memory is not utilized to conserve power.

In terms of display connectivity, AMD now supports DisplayPort 1.2 which allows them to drive up to 4 displays. Other than that the platform didn't change much. There will be a new version of the Fusion Controller Hub (FCHs), namely the A85X on the desktop. Legacy PCI will be thrown out the door. There are two additional SATA 6Gbps ports, totaling eight now. Also the controller will now include RAID5 support. This seems to be the way to go for upcoming FM2 motherboards. As a reminder, socket FM2 won't be pin-compatible with the predecessor FM1.

Another feature that got a major overhaul was TurboCore which is incorporated in its third incarnation in Trinity. Trinity not only supports different boost steps for the CPU, but also the GPU. The APU manages its TDP budget and optimizes for the specific workload it is given. AMD gave a good overview of how it might work out in practice. If only a single CPU core is loaded the maximum boost frequency is selected. In the case of the 4600M used as an example this would be 3.2GHz - quite high for a notebook.