Feature Articles

AMD FX Processors - All You Need to Know of Bulldozers and the FX-8150

By Wong Chung Wee - 13 Oct 2011



For the CPU market, the year of 2011 heralds the advent of the concept of ‘fusion’. At the simplest level, the gist of the idea is the merging of the CPU and GPU processing capabilities into a single processing die. Intel’s Sandy Bridge architecture as well as AMD’s Zacate (part of the Brazos platfom) and Llano (part of the Sabine platform) processors will undoubtedly cast doubts on the relevance of the traditional CPU. However, AMD does recognize the needs of the enthusiast rig builders who clamor for the performance and ability to overclock the conventional setup of a traditional processor with discrete graphics computing in the form of a standalone graphics card.


In Anticipation of the Bulldozer

After the introduction of its Phenom II X6 processor, AMD had officially brought its server/workstation series to the desktop, with a scaling up from a quad-core architecture of the Phenom II to six cores on a single die. AMD also introduced the Turbo Core which is a feature that dynamically scaled up the processor's clock speeds when the application load on the processor is lightly threaded. Idle cores are almost switched off completely and consume close to zero power while the remaining, active cores are bumped up.

With the launch of the updated Phenom II processors, speculations have been rife over the arrival of AMD's next generation CPU architecture codenamed Bulldozer. High hopes have been pinned on its lineage as the Bulldozer carries AMD's hope of getting back on level terms with Intel on the desktop processor front. Although the fusion concept has been the talk of the town since the beginning of the year, the desktop and server markets still remain very significant and it's where AMD has been finding it extremely difficult to find its foothold, especially in the mid-range and higher end segments.

On the 12th of this month, AMD finally heralded the arrival of the Bulldozer CPU architecture and debuted three processors SKUs. Press kits containing its current top of the line processor, the FX-8150 were shipped to reviewers worldwide and we are honored to introduce it here.


Building the New Architecture

According to AMD, the Bulldozer based processors have been designed and built from ground up. It is AMD’s introduction of a new CPU architecture since the Phenom II. While the new architecture is named "Bulldozer", the actual processors that first feature the Bulldozer architecture are codenamed Zambezi. As of 12th of October, Zambezi has been officially launched and will be easily retailed under the AMD FX family of processors. The current offerings are two eight-core processors FX-8150, FX-8120 and a 6-core FX-6100. This means, the AMD FX family is the first eight-core processor in retail, though we'll soon share that it's not the same kind of 'core' we're accustomed to.

Unlike most traditional core designs that have a single integer and floating point scheduler and execution units, AMD has deviated from this design by analyzing application usage and maximizing processing throughput for a given silicon area. The Bulldozer's 'core' consists of dual integer units that share a common high performance floating unit, along with other common stages like fetch, decode and a shared L2 cache. Since the Bulldozer 'core' is now closer to a dual-core processor in functionality, AMD is now terming this as a "module" which can be viewed as a microarchitecture building block on the die. The block diagram below is the Bulldozer module as described. On the top of the line FX-8150, four of these Bulldozer modules make up its specified eight cores in total.

Each Bulldozer module has a front-end unit designed to ensure both cores are constantly fed with data. It shares the FP scheduler among the two cores and each core has its own integer scheduler. AMD claims that the new design will let the chip make better use of available throughput and will offer substantially higher integer performance.

Though each Bulldozer module has two 'cores', they aren't the traditional cores that we've familiar with. Instead, each module has constituent parts of two traditional CPU cores. Hence, calling the FX-8150 processor an eight-core chip is not entirely accurate, but it's more of a quad-module, eight-core part processor.

Each Bulldozer module is tied with 2MB of L2 and is further augmented with 2MB of L3 cache. In total, the top of the line FX-8150 has 8MB of L2 and L3 cache respectively. The L3 cache is shared between the cores on each module. The top of the line processor from its predecessor family, the Phenom II X6 1100T Black Edition has only 3MB of L2 cache and double of that amount for its L3 cache in total. Just from the cache hierarchy perspective, the new AMD FX family is looking far better equipped to tackle new generation of requirements - especially from its modular nature.

Besides increasing the amount of cache memory, AMD engineers have redesigned the floating point unit of the Bulldozer CPU to allow for resource sharing between each core on the module. The FPU has been improved to support new instructions like FMA4 and XOP. These new instruction sets are mainly for HPC applications and other applications that require complex algorithms. There is also support for the latest SSE 4.2 instructions sets which mark an improvement over the existing Phenom II X6 and X4 processors and are now much closer to instruction set support of Sandy Bridge processors.

The FPU has been improved to support many new instructions and it now allows resource sharing between cores. There are two 128-bit FMACs shared per module, allowing for two 128-bit instructions per core or one 256-bit instruction per dual-core module.

There are trade-offs with this new designed FPU as according to the spokesperson from AMD, the Bulldozer processor is unable to process older x86 instructions in an optimal manner and might result in lower scores in current benchmarking tools. However, future application and games will be optimized for the new floating point instruction sets. In additional to software updates, improvements to scheduler of operating systems will ensure optimized data loads for the AMD FX processor. Windows 8 (currently in its developer edition) has a optimized scheduler that can better align threads to the proper cores as well as control the power settings of the processor.

With an updated operating system scheduler, threads 1a and 1b are directed to the same core while the unused cores are parked so that AMD Turbo Core is enabled. This is as opposed to a non-updated OS scheduler (like Windows 7 or earlier) which might send thread 1b to be executed in another module, and thus may not invoke Turbo Core with too many cores used (depending on workload and power used).

AMD's Turbo Core technology has been updated to include a new mode that can turbo boost all cores for a time when there is extra TDP headroom. This technology is AMD's answer to Intel's Turbo Boost. AMD's version of boosting the core's frequency is different from Intel's interpretation. In order to verify the significance of the improved Turbo Core and Bulldozer's core design, we would have to wait for the release of Windows 8 and other updated software for our benchmarking purposes.

There is also the issue of memory bandwidth as the FX processor is paired with a memory controller with the now standard two DDR3 memory channels. This may become a bottleneck for the eight core FX-8150 model in very heavy workloads. This design consideration is to maintain backward compatibility and we feel that such nitpicks are miniscule in the grand scale of things. Besides, we've previously tested Nehalem's tri-memory controller architecture and it didn't pose too much of an advantage for the typical end-user. The upside is that it now supports DDR3-1866, so memory bandwidth has improved.

AMD FX Processors Specifications
Processor Model Clock Speed L2 Cache L3 Cache HyperTransport Bus
Max TDP (W) Retail Price (US$)
AMD FX-8150 3.6GHz (3.9GHz Turbo Core) 8 x 1MB 8MB 2.2GHz 125 ~$245
AMD FX-8120 3.1GHz (3.4GHz Turbo Core) ~$199
AMD FX-6100 3.3GHz (3.6GHz Turbo Core) 6 x 1MB 6MB 2.0GHz 95 ~$175

The AMD eight core FX8150 is priced competitively at US$245. This is AMD's strategy to give rig builders more savings so that they can splurge on a discrete graphics card of higher specifications for their demanding computing needs. As compared with the existing crop of Phenom II processors, for just an additional US$40, consumers can make the leap to top-of-the-line offering from this new generation of Bulldoze-based processors. Such an offer is certainly compelling for consumers who have been waiting to upgrade their desktop processors - especially if you've a compatible platform. In terms of pitting itself against Intel's Sandy Bridge processors, AMD positions the FX family strategically between the Intel Core i5 and Core i7 range of processors. We'll be sure to give you the full comparison breakdown in the near future.

For comparison sake, here's the latest Black Edition AMD CPU offerings are the Phenom II X6 and X4 processors which we have highlighted in the table below (accurate as of October 2011):-

AMD Phenom II X6 and X4 Processors Specifications (Black Edition)
Processor Model Clock Speed L2 Cache L3 Cache HyperTransport Bus
Max TDP (W) Retail Price (US$)
AMD Phenom II X6 1100T 3.3GHz (3.7GHz Turbo Core) 512KB x 6 6MB  2.0GHz 125W ~$205
AMD Phenom II X6 1090T 3.2GHz (3.6GHz Turbo Core) ~$185
AMD Phenom II X4 980 3.7GHz 512KB x 4 ~$185
AMD Phenom II X4 970 3.5GHz ~$155

The most commonly available boxed non-Black edition processors locally are the Phenom II X6 1055T and the Phenom II X6 1075T.

AMD Phenom II X6 Processors Specifications
Processor Model Clock Speed L2 Cache L3 Cache HyperTransport Bus
Max TDP (W) Retail Price (US$)
AMD Phenom II X6 1075T 3.0GHz (3.5GHz Turbo Core) 512KB x 6 3MB  2.0GHz 125W ~$181
AMD Phenom II X6 1055T 2.8GHz (3.3GHz Turbo Core) ~$165

AMD's business strategy is to entice the discerning consumer to part with a little more budget to acquire the top of the line Bulldozer CPU with its full eight-core glory. With its seemingly high hopes pinned on the Bulldozer processors, we chanced to ask the AMD spokesperson if he could confirm rumors of the cessation of the production of the AMD Phenom X2 and X4 processors. Alas, we failed to get confirmation on that piece of information.

The recommended chipset for the Bulldozer processors is the AMD 9-series, especially the AMD 990FX chipset (to unleash the full potential of the platform). For people who have already invested in 8 and 7-series AM3+ motherboards, take heart that your boards would be ready for processor upgrades after a BIOS update from your official board manufacturers.

Although AMD has not officially tested the Bulldozer processors with the older chipsets, it should eventually work with any Socket AM3+ certified board. Meanwhile, AMD recommends their "Scorpius" platform to tap the full processing horsepower of the Bulldozer processors. The platform comprises a 9-series chipset motherboard, an AMD Radeon HD 6000 series graphics card and of course the AMD FX processor. Ideally, the graphics card should be a Radeon HD 6850 class or higher for an effective gaming platform.

This is an example of a top-end Scorpius platform - and AMD FX processor coupled with an AMD 990FX chipset motherboard and graphics cards of the Radeon HD 6800 series or better. Note that the DDR3-1866 is supported on the new AMD FX processor for improved memory throughput.

For overclockers, the FX processors come with multiplier unlock and to prove its mete, AMD has already set a world record for the fastest desktop processor achieved with liquid helium cooling. Besides this feather in AMD’s hat, we feel that AMD new FX processors have the capability to vie for price-performance throne in enthusiast desktop systems and we intend to find out soon.

Join HWZ's Telegram channel here and catch all the latest tech news!
Our articles may contain affiliate links. If you buy through these links, we may earn a small commission.