AMD Athlon 64 & Athlon 64 FX - It's Judgment Dayby Anand Lal Shimpi on September 23, 2003 1:25 PM EST
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AMD's Gem: Athlon 64
When you have an architecture that has been talked about publicly for a couple of years and when all of your partners have had access to CPUs for almost as long, it becomes very tough to keep things a secret. Leaks occur and it would be an understatement to say that AMD was plagued by a few leaks, so most of the information you're about to hear has been published elsewhere and already alluded to.
With that said, AMD has brought two versions of their K8 architecture to the desktop market - branded the Athlon 64 and the Athlon 64 FX. The Athlon 64 is the 754-pin ClawHammer that we've been hearing about all this time, while the Athlon 64 FX is little more than a higher clocked 940-pin Opteron.
Let's start with the regular Athlon 64; contrary to surprisingly popular belief, the regular Athlon 64 does include an on-die memory controller - what it doesn't include is the on-die 128-bit memory controller found on the Opteron. Instead, you will find only a single-channel 64-bit memory controller with the Athlon 64. This on-die memory controller supports regular unbuffered DDR SDRAM at speeds of up to DDR400.
The other major difference between the Athlon 64 and the Opteron is that the Athlon 64 only has a single Hyper Transport link. Remember that the K8 architecture does not have any external "Front Side Bus" instead, serial Hyper Transport links connect the CPU to external chips such as a South Bridge, AGP controller or another CPU. With only one Hyper Transport link, there's no hope for the Athlon 64 to be used in multiprocessor environments as the sole Hyper Transport link would be tied up by the South Bridge/AGP controller. This lack of multiprocessor support is in direct contrast to the "lack" of multiprocessor support with the Athlon XP, which you could use in multiprocessor configurations; with the Athlon 64 it is physically impossible (unless you don't want any BIOS, hard drive or expansion slot support).
AMD originally announced that the Athlon 64 would have a 512KB L2 cache, however after continued delays and increased competition the Athlon 64 was given a full 1MB L2 cache. As we mentioned before, the 128KB L1 cache remains unchanged from the original Athlon XP and its exclusive nature means that the Athlon 64 has a total of 1088KB of cache for data storage (the remaining 64KB is for instruction storage).
The Athlon 64 will continue with AMD's model numbering system, although with a revised test suite. The end result is that AMD is much more conservative with their ratings, meaning that an Athlon 64 3200+ is inherently faster than an Athlon XP 3200+, despite carrying the same model number. As you've undoubtedly heard, the only Athlon 64 available at launch will be the 3200+, which will run at a 2.0GHz clock speed. The 2.0GHz clock speed is arrived at by taking the 200MHz Hyper Transport clock and multiplying it by a 10.0x clock multiplier. Currently there isn't a way to adjust the multiplier of Athlon 64 CPUs, so the potential for overclocking exists by increasing the Hyper Transport clock.
In Q4 AMD will launch the Athlon 64 3400+, which we'd assume would be clocked at 2.2GHz. The 3400+ will be the last Athlon 64 for 2003, and although we will see lower clocked versions in the mobile space, that will be it for desktops. The 3400+ will be introduced at around $600.
The Athlon 64 3200+ will sell for $417 in 1,000 unit quantities.