Processor Obfuscation and You: An Update on AMD and Intel CPUsby Kristopher Kubicki & Jarred Walton on May 17, 2005 12:00 PM EST
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AMD ProcessorsWhen we set out to write this guide, AMD processors were the most blatant offenders. There are four AMD cores shipping right now on the desktop, two (Hammer and Newcastle) of which also have non-standard variants with cache disabled and relabeled as other chips. Considering that most Athlon 64 processors have a different clock from core to core while the product name remains the same, it becomes real easy to get the wrong chip in many instances.
First, let's take a look at the code names and features of all the currently shipping AMD processors. We'll break it down by platform to keep things manageable.
|Core Name||CPU Name||L2 Cache||Process||Notes|
|Venice||Athlon 64||512K||90nm||SSE3 enabled|
|San Diego||Athlon 64/FX||1024K||90nm||SSE3 enabled|
|Manchester||Athlon 64 X2||2 x 512K||90nm||SSE3 + Dual Core|
|Toledo||Athlon 64 X2||2 x 1024K||90nm||SSE3 + Dual Core|
Socket 754For those on a budget, the Socket 754 Sempron parts might be interesting. The 754 parts are decent performers, although they lack the 64-bit extensions, should you want them in the future. If you do get a Sempron, we'd recommend the 90nm Palermo (BA/BO) cores rather than the 130nm Paris (AX) cores. At the time of publication, the only Paris Sempron comes in the form of the Sempron 3100+, and it is starting to be phased out. Unfortunately, we stumble into our first problem here: there are two versions of Palermo [RTPE: Palermo] floating around. The first generation of Palermo processors uses the "D0" stepping while the second uses the "E3" stepping. On Semprons, the difference in steppings is not dramatic, since the better extensions are in the Athlon 64 chips anyway. However, the "E3" chips - denoted with "BO" in the SKU - are slightly more desirable as they are supposed to run a little bit cooler than their "D0" or "BA" predecessors.
Also keep in mind that Sempron cache sizes differ every other processor; i.e. the Sempron 2600+ has 128KB of L2 cache, the 2800+ has 256KB, 128KB for the 3000+... and so on. While the onboard memory controller on the Socket 754 and Socket 939 processors helps to mitigate the impact of the reduced cache size, it's almost always desirable to grab the chip with the bigger cache if you can afford it (at least when the difference is between 128KB and 256KB). Don't let the different L2 cache sizes fool you though; all of these chips are Palermo.
So, now that you are thoroughly confused, let's make things even more confusing; enter the ubiquitous Socket 754 Athlon 64 processors. There has been talk about EOL (End of Life) on the Socket 754 desktop platform, and if that is the case, then we suspect that the Athlon 64 3700+ (2.4 GHz with 1MB L2 cache) will remain the fastest option. The 3700+ as well as the 1MB cache 3200+ and 3400+ all use the Clawhammer core, while the 512K cache chips all use the later Newcastle core. Clawhammer appears to have been a time-to-market decision, as it was expensive to manufacture due to the size. It also generates more heat than Newcastle, which isn't too surprising. The added cache adds anywhere between 3 to 10 percent performance, depending on application, which means that most people wouldn't notice the difference between the 2.4 GHz 3400+ Newcastle and the 2.4 GHz 3700+ Clawhammer.
Hammer chips (Sledgehammer and Clawhammer) are the oldest in the Athlon 64 fleet, and still us the "C0" stepping. "C0" was the original Athlon 64 (and Opteron) stepping, so if you plan on buying a Hammer chip, you're planning on buying a two-year-old processor at this point. Generally speaking, you can easily determine if a processor is a Hammer chip by the SKU; if the SKU ends in "AP" (Socket 754 512KB L2), "AR" (Socket 754 1MB L2) or "AS" (Socket 939), you're looking at a Hammer chip. Newcastle chips utilize the "CG" stepping and are slightly newer than their Hammer counterparts. You can usually spot a Newcastle processor due to the "AX" in the product SKU. Unlike Hammer chips, all Newcastle processors use "AX" regardless of cache size, including the tiny Sempron 3100+ that we mentioned earlier - which AMD dubbed Paris.
As far as overclocking is concerned, neither the Newcastle nor Clawhammer cores do very well, though the Newcastle tends to be a bit better. 2.5 GHz is typically the maximum speed that they'll run, and many of them won't handle more than about 2.4 GHz. If you want to try overclocking, your best bet is probably the Newcastle 3200+, which is relatively inexpensive and can often reach nearly the same performance level as the 3700+. Motherboard choice will also play a role in overclocking, with the DFI LANParty UT 250Gb being the star of the platform. If you already have a socket 754 motherboard, however, we'd recommend that you stick with that rather than buying the DFI simply for overclocking - you'll have better luck with the 90nm 939 parts if overclocking is what you're after. The 90nm Palermo Sempron chips seem to overclock quite well - 2.5 GHz and above can usually be reached - but the reduced cache sizes bring diminishing returns. Coupled with the need for decent RAM or the use of an asynchronous memory bus, the benefits of overclocking Sempron chips are pretty slim. In the end, a 2.5 GHz 256K Sempron will roughly match a 2.2 GHz 512K Athlon 64 on socket 754.
If you're only running a 2800+ or Sempron, it may be worthwhile to spend $200 to $300 for a faster processor, but ultimately, the platform is going to be the limiting factor. No dual core processors are planned for 754, and although PCIe may appear in a few motherboards, we have a hard time recommending such an option. It's also worth noting that the maximum supported RAM on Socket 754 motherboards is 3GB, meaning that true 64-bit support is somewhat debatable. For most Socket 754 owners, we'd say stick with what you have until you're no longer satisfied with the performance, and then upgrade to a new platform. For those who are looking to buy a new computer, we'd urge you to stay away from Socket 754 unless budget is the overriding concern. It's not necessarily a bad platform, but $50 more would allow you to upgrade to Socket 939, which we feel is the better choice.