Better integration for power savings
Llano's battery life is pretty good, but AMD claims Trinity is even better, with run times in some configurations extending as far as 10 hours. One very impressive number in this regard is the chip's idle power draw of 1.08W. Battery run times will, of course, depend on more than just the CPU's power consumption, but Trinity looks to be doing its part to conserve power.
Power-efficient performance should get a boost thanks to more capable power management and dynamic clock speed scaling. Llano could only trade power in one direction, with the CPU scaling up or down via Turbo Core depending on the needs of the IGP. Trinity's IGP can join the game, now, too, allowing the whole chip to adjust its performance in response to the current workload.
The example above shows how the A10-4600M's IGP and CPU clock frequencies change in response to different workloads. A heavy CPU load with light graphics use results in a moderate IGP clock and higher CPU frequencies. The CPU speed then varies based on the number of threads active; with a single thread, the A10 CPU can reach 3.2GHz. On the other hand, for a GPU-intensive application with modest CPU needs, the IGP clock jumps up and the CPU speed scales down.
Since they're based on Piledriver, the CPU modules in Trinity have a much more capable implementation of Turbo Core than Llano. Llano has only one P-state above its stock clock speed. The A8-3500M's base frequency is 1.5GHz, and when Turbo kicks in, the clock jumps to 2.4GHz. Trinity has finer-grained control, with four P-states for Turbo Core. Trinity is also able to respond much more quickly to changes in activity and die temperatures, thanks to an onboard power-management microcontroller and an architecture that's designed to operate well at different frequencies across a range of voltages.
One way Trinity manages to achieve such low power draw at idle is more extensive power gating. In addition to power gates for the IGP and the two CPU modules, this chip adds gates for the north bridge, the PCIe interface, and the display PHY. When those portions of the chip aren't in use, they can be shut off entirely, eliminating even the leakage power that would otherwise be going to them.
The conservation effort extends to the rest of the platform, too. Trinity's memory controller can adjust DRAM frequencies on the fly in order to conserve energy, and it supports the low-power DDR3 standard for driving DIMMs at 1.25V. The VRMs can make faster transitions, improving efficiency. Also, the number-one activity for nearly all computer users is now more economical: staring at a static screen. Trinity can refresh a static display from a single memory module, allowing the other DIMM to scale back or to power down. The chip has more buffering for display memory, too, which should save power that would otherwise be spent on memory I/O.
Accelerating accelerated computing
AMD has talked a good game about CPU-GPU convergence and accelerated computing for a while now, but it is also laying the foundation for true GPU-IGP cooperation. One key bit of plumbing on that front is something called the Fusion Compute Link. The FCL replaces the PCIe communication channel between the CPU and GPU in a merged chip like Trinity. Llano's first-generation FCL had only modest bandwidth, but AMD promised to invest more in this connection over time. Trinity's FCL is 128 bits in each direction. This connection allows the IGP to access the CPU's memory space coherently, and it gives the CPU a window into the IGP's dedicated frame buffer. Given the right programming model, which AMD is pioneering with its software work on the Heterogeneous System Architecture, the FCL could become important in future converged applications, where the IGP and CPU might team up to manipulate data in the same memory.
The FCL augments the IGP's primary path to system memory, which is two pairs of 256-bit links (one in each direction) between the graphics memory controller and the north bridge.
Trinity is ready to support merged applications with discrete GPUs, too. Its IOMMU will allow the shaders in PCIe graphics cards to operate directly on main memory, and it's capable of supporting GPU virtualization.
The new A-series APUs
Naturally, AMD has a range of Trinity-based APUs on offer. The fastest model is the A10-4600M, which we've already seen in our dynamic power scheme example. The A10-4600M is also the chip we have for review today. As you can see, it has all of Trinity's cores and cache enabled, running at aggressive clock speeds. With its 35W TDP, the 4600M will serve nicely to illustrate AMD's progress since the Llano-based A8-3500M we reviewed last year—and have brought back here for an encore. AMD expects the A10 series to make its way into laptops costing $700 and more, where it will compete with the lower end of the mobile Core i7 line and the high end of the Core i5 lineup.
We have a couple of laptops based on Intel chips in the same basic class as the A10-4600M for comparison, too. The Core i7-2670QM is a quad-core Sandy Bridge with a 2.2GHz base clock and a 3.1GHz Turbo peak that is selling in laptops costing $659 and up at Newegg. The Core i7-3720QM is an Ivy Bridge-based quad-core in the same price range, although it's too new to have a robust selection of systems available. Those few that are available currently cost quite a bit more than $700. A bigger wrench in the works is the fact that both Intel chips have 45W TDP ratings, so they have more room from which to extract performance than the A10-4600M. The most direct competition from Intel at present may be the Sandy Bridge-based Core i7-2640QM, which has a 35W TDP and costs about $30 less than the i7-3720QM, but it is a near run thing. AMD has positioned the A10 very close to those Intel quad-cores, obviously quite intentionally.
The rest of the lineup plays out much as one might expect. The A8-4500M will occupy systems costing $550 or more, facing off against the lesser Core i5s and greater Core i3s. The A6-4400M, with only one compute module (and thus two cores) enabled, will do battle with the Core i3 in laptops above the $450 mark. As far as we know, the A6 parts are actually quad-core Trinity chips with two cores disabled. AMD wasn't willing to disclose any plans to produce a natively dual-core version of Trinity.
The most interesting Trinity parts, in our view, are the 25W and 17W models. The 17W version is the one destined for those ultra-thin MacBook Air clones, and we're very much intrigued by its potential. It may prove to be a nice alternative to the dual-core version of Ivy Bridge, once the dual Ivy chip arrives later this summer.
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