4.5 Forthcoming AMD and Intel Processors

Intel and AMD constantly strive to out-do each other in bringing faster and more capable processors to market. In late 2003 and into 2004, each company will be ramping up its new-generation desktop processors. Although the current Athlon XP and Pentium 4 processors will continue to sell in large numbers throughout 2003 and into 2004, the future definitely belongs to these new processor lines. AMD hopes to get a foothold in the corporate market and to increase their general market share with their new desktop processors, but Intel has some plans of its own to protect its 80%+ general market share and its nearly 100% corporate market share.

As we write this in July 2003, only the Opteron processor is shipping, and only in limited numbers. The Athlon 64 and the Prescott/Pentium 5 are not yet shipping and we have been unable to get pre-production samples from AMD and Intel. Accordingly, much of this section is speculative, based on published information that is subject to change, industry rumors, and informed speculation. However, we thought it worthwhile to include the best information we had available as we went to press, because even imperfect or incomplete information may be useful to our readers.

4.5.1 AMD Opteron and Athlon 64

By mid-2002, AMD was struggling to produce Athlons that could match Pentium 4 performance. By July 2003, it was obvious to nearly everyone that the Athlon XP had reached the end of the line and that the 3200+ would almost certainly be the final Athlon XP processor. AMD was able to push the Athlon core further than anyone expected, eventually reaching a core clock speed of 2.2 GHz in the Barton-core Athlon XP 3200+ model. AMD also expanded L2 cache from 256 KB on earlier cores to 512 KB on the Barton core, and increased FSB speeds from 266 MHz to 333 MHz and eventually to 400 MHz on the final Athlon XP models.

But all of these enhancements yielded only marginal performance improvements over earlier Athlon models. The real problem was that the Athlon core itself had reached its limits, while Intel's Pentium 4 core wasn't even breathing hard. AMD badly needed an entirely new processor core if they were to compete with Intel on anything like a level playing field.

In April 2003, AMD shipped their new-generation processor, code-named K8 or Sledgehammer, officially named Opteron, and ironically dubbed "Lateron" by pundits because of the repeated and lengthy delays AMD suffered in bringing this processor to market. (Nor is AMD alone in having evil nicknames applied to its processors. Some wags called the original Itanium 1 the "Itanic" because, like its namesake, it sank without a trace.)

AMD will produce two processor lines based on the K8 core. The Opteron is intended for servers, and began shipping in April 2003. The Athlon 64 is a cut-down version of the Opteron intended for desktop systems, and is to begin shipping in September 2003. The key feature of both processors is that they support both 32-bit and 64-bit instructions, and can dynamically alternate 32- and 64-bit threads.

In contrast to the 64-bit Intel Itanium, which executes 64-bit code natively but 32-bit IA-32 code only via slow translation, the Opteron and Athlon 64 are 64-bit processors that can execute 64-bit code using the AMD64 instruction set?called "long" mode?and can also execute standard 32-bit code natively, called "legacy" mode. To support 32- and 64-bit operations in one processor, AMD modified the Athlon XP core to add eight 64-bit general-purpose registers and eight 64-bit versions of the original eight 32-bit general purpose registers. These 64-bit registers are accessible only when the processor is operating in long mode. In legacy mode, the Opteron and Athlon 64 processors appear to 32-bit software as a standard 32-bit Athlon processor.

The Opteron and Athlon 64 are incompatible with current chipsets and motherboards, so using either requires buying or building a new system. As of July 2003, Opteron systems and motherboards are in limited distribution. We expect Athlon 64 products to become available in September 2003.

4.5.2 Opteron

The Opteron is based on the variant of the K8 core codenamed Sledgehammer. Various Opteron models support 1-, 2-, 4-, and 8-way operation and are targeted at servers. AMD plans to produce at least three Opteron series. Opteron 100-series processors support only 1-way processing, and are due in September 2003. Opteron 200-series processors support 1- and 2-way processing, and shipped in April 2003. Opteron 400-series processors support 1-, 2-, 4-, and 8-way processing, and are to ship in September 2003 and into 2004.

Rather than the clock speed designations or QuantiSpeed model numbers AMD used for earlier processors, AMD assigns each Opteron model an arbitrary number to indicate relative performance. For example, the Opteron processor roadmap includes the 140, 240, and 840 models, which operate at 1.4 GHz; the 1.6 GHz 142, 242, and 842 models; and the 1.8 GHz 144, 244, and 844 models. AMD plans to release later Opteron models operating at 2.0 GHz (presumably the 146, 246, and 846 models), as well as models operating at 2.2 GHz (148, 248, and 848).

Opteron processors use 6.4 GB/s HyperTransport Technology (HTT) channels to provide a high-speed link between the processor components themselves and to the outside world. The Opteron has three HTT channels, which may be either of two types. Coherent HTT channels link the processor to other Opteron processors. Opteron 100-series, 200-series, and 800-series processors have zero, one, or three coherent HTT channels, respectively. Standard HTT channels link the processor to I/O interfaces such as a Southbridge or PCI Express bridge.

Do not confuse AMD HTT (HyperTransport Technology) with Intel HTT (Hyper-Threading Technology). You'd think they could come up with different TLAs. It isn't like there aren't lots of letters to choose from.

The Opteron features a 1024 KB L2 cache and a dual-channel DDR333 memory controller, which uses a 144-bit interface that requires 72-bit ECC memory. Relocating the memory controller from the chipset, where it has traditionally resided, directly onto the processor core allows memory to be more tightly integrated with the processor for higher performance. The downside is that the Opteron is limited to using memory no faster than DDR333 unless AMD changes the processor core itself, or unless a chipset maker adds an external memory controller.

Informed sources speculate that AMD may tweak the shipping K8 core to add support for DDR400 and perhaps DDR533. Support for DDR-II will come no earlier than mid-2004, pending JEDEC approval of a final DDR-II specification.

The Opteron uses Socket 940, newly introduced by AMD for this processor. Relative to Socket 462, those extra contacts are used primarily to support the three HTT channels.

4.5.3 Athlon 64

The Athlon 64 processor is based on the variant of the K8 core codenamed Clawhammer. The Athlon 64 supports 1- and 2-way operation, is due in September 2003, and is targeted at desktop systems. The Athlon 64 differs from the Opteron in the following important respects:

HyperTransport Technology channels

Rather than the three HTT channels used by the Opteron, the Athlon 64 has only one HTT channel.

Memory controller

Rather than the 144-bit dual-channel DDR333 ECC memory controller used by the Opteron, the Athlon 64 has a 64-bit single-channel DDR333 non-ECC memory controller. (Shipping models may include DDR400 support.) The narrower memory interface of the Athlon 64 means its memory bandwidth is half that of the Opteron. Like the Opteron, the Athlon 64 integrates the memory controller onto the processor.

Cache size

The Athlon 64 and Opteron both have the AMD-standard 128 KB L1 cache, with 64 KB allocated to instructions and 64 KB to data. Opteron processors provide 1 MB of L2 cache. Athlon 64 processors are available with either 256 KB or 1 MB L2 cache. Our moles tell us that for performance reasons, AMD may decide to ship the "small" Athlon 64 with 512 KB L2 cache rather than 256 KB.

Chipset support

Most Opteron systems will be built around the server-class AMD 8000-series chipset. Most Athlon 64 systems will use desktop-class chipsets such as the nVIDIA nForce3, the VIA K8T800/K8M800, and others. Based on our experiences with the nForce and nForce2 Athlon chipsets, we expect the nForce3 to be the best Athlon 64 chipset.

The Athlon 64 uses Socket 754, another new AMD socket. As with Socket 940, the additional contacts are necessary to support the single HTT channel supported by the Athlon 64. Because the Athlon 64 has only one HTT channel, it can use the smaller socket.

Table 4-6 details the important characteristics of the Opteron and Athlon 64 processors, with the Barton-core Athlon XP shown for comparison. Most of the items are self-explanatory, but a couple deserve comment.

Generation

AMD regards the Athlon XP as seventh-generation and the Opteron/Athlon 64 as eighth-generation. We consider both of those processor families to be hybrids, straddling the generational boundaries defined by Intel processors. In particular, the 64-bitness of the Opteron and Athlon 64 give them a definite claim to eighth-generation status, but architecturally they remain near relatives of the hybrid sixth/seventh-generation Athlon XP.

Fabrication process

With the Opteron and Athlon 64, AMD uses the Silicon-on-Insulator (SOI) process rather than the traditional CMOS process. SOI offers potentially huge benefits, but at a correspondingly high risk. During the first half of 2003, AMD's problems with SOI in getting high yields at fast clock speeds were widely reported in the industry press. We think the most important issue for the new AMD processors is how well and how quickly the AMD Dresden fab will be able to master SOI production. If they succeed, they will produce high yields of the new processors and be able to scale clock speeds up quickly. If they fail, the Opteron and Athlon 64 will be expensive to produce and will languish at lower clock speeds. The phrase "bet the company" is often used in the high technology field, but in this case we think AMD is indeed betting the company on the success of their SOI process.

4.5.4 Intel Pentium 5?

Intel and AMD play a constant game of leapfrog. The introduction of the Opteron/Athlon 64 almost demanded that Intel introduce a new processor of its own. That processor is the Prescott-core Pentium, due in the fourth quarter of 2003, which Intel may or may not call the Pentium 5.

On balance, we think Intel will decide to name their new processor the Pentium 5, both for marketing reasons and for technical reasons. From a marketing standpoint, Intel would clearly like to counter the Opteron and Athlon processors with a newly-named processor of their own. From a technical standpoint, the improvements in architecture and instruction set are sufficient to justify the Pentium 5 name for the Prescott-core processor.

No matter what Intel chooses to call this processor, it is a significant improvement on the current Northwood-core Pentium 4. Relative to current Northwood-core processors, the Prescott-core processors increase L1 cache size, boost L2 cache from 512 KB to 1024 KB (matching the new AMD processors), and increase pipeline depth to enable higher core frequencies.

Just those enhancements would have made life difficult for the new AMD processors. But a more significant enhancement lurks within Prescott. The Prescott New Instructions (PNI) are 13 new instructions that extend the SSE and SSE2 multimedia instruction sets used by earlier Intel processors. In particular, three of the new PNI instructions are worth noting. One adds support for AV encoding?as opposed to AV decoding, which was supported by earlier Intel processors?and two improve thread control for Hyper-Threading Technology (HTT) operations.

The new HTT thread control instructions are likely to boost performance substantially, with less sensitivity to application mix. In the past, the benefit of HTT depended largely on the specific applications being run. Some applications showed major performance improvements with HTT, most applications showed no change, and some actually ran slower with HTT enabled. The improved HTT threading support available with PNI means that HTT will become more generally useful. For more information about PNI, visit http://cedar.intel.com/media/pdf/PNI_LEGAL3.pdf.

Prescott-core processors may also have a major hidden feature. We admit that this is pure speculation on our part, but we do have some historical evidence for our beliefs. Intel built Hyper-Threading Technology into Northwood-core processors, where it remained hidden until Intel chose to reveal it. We think history may repeat itself. Intel may have embedded their Yamhill technology into Prescott as a hidden feature.

Intel's world view is that 32-bit processors are sufficient for desktop systems, that only datacenters require 64-bit processors, and that 64-bit processors should operate natively in 64-bit mode rather than as 32/64-bit hybrids. But Intel always has a Plan B, and in this case Plan B is Yamhill. Yamhill is, in effect, Intel's version of AMD's hybrid AMD64 architecture. Intel would prefer to drive people to its native 64-bit Itanium architecture. But if that fails and AMD64 catches on, Intel can spring Yamhill as a nasty surprise to AMD. Don't be surprised if that happens.

Table 4-7 shows the important characteristics of the Prescott-core "Pentium 5", with the Northwood-core Pentium 4 shown for comparison.

4.5.5 Our Thoughts

We won't comment in detail on server processors, because we don't understand that market well enough. We note, however, that IT managers are notoriously conservative in adopting new platforms, and the perception of Intel as the tried-and-true 64-bit solution, particularly with regard to chipsets, probably militates against the broad acceptance of the Opteron in the datacenter. We're sure that the Opteron will have some "wins", but overall we think that 32-bit Intel processors will continue to dominate PC-server space. Those who need the additional memory addressability and other features of 64-bit processors will probably continue using heavy iron, at least in the short term.

On the desktop side, the picture isn't much better for AMD. We think the Intel Pentium 5 (or whatever Intel chooses to call it) will walk all over the Athlon 64. Although the Athlon 64 runs 32-bit code competently?something Intel has never been able to achieve with its 64-bit processors?its forte is 64-bit operations, and for now 32-bit operations are sufficient for the desktop. The only 64-bit operating system available is Linux, although Microsoft promises a 64-bit Windows Real Soon Now. Even if that comes to pass, the dearth of 64-bit applications programs means that the Athlon 64 will be operating in 32-bit mode nearly all the time.

Considered as a 32-bit processor, the Athlon 64 is in effect a slightly enhanced Athlon XP. It operates at a severe disadvantage relative to the Prescott-core Pentium. AMD had severe teething pains getting the K8 core running faster than 1.8 GHz, and we do not expect the K8 core to scale nearly as well as the new 0.09m Intel core. We think it likely that when the new Intel core debuts at 3.4 GHz, it will match or exceed the fastest Athlon 64 model in most 32-bit operations. And, while AMD has to work very hard for each increment in Athlon 64 clock speed, we expect the new Intel core to scale effortlessly to 5 GHz or faster.

Although we admire AMD and appreciate the results of their competition with Intel, we're forced to conclude that AMD is likely to be an also-ran in the desktop processor race throughout 2003 and well into 2004. The arrival of 64-bit Windows and 64-bit applications may help somewhat, but we think it will be insufficient to turn the tide. Certainly, 64-bit processing (and memory addressability) will be a blessing for some people. Those who work with huge databases or do serious image processing and video work can use every bit of horsepower and memory they can get. But for the most part we think 64-bit processing for the desktop is a technology of the future, and is unlikely in the short term to create a large demand for the new 64-bit AMD processors.