The Newcomer: AMD Athlon64
The socket on the Athlon64 has 754 pins; the processor itself sits in a flip-chip BGA package. Its metallic surface forms what's known as the heat spreader that enables improved carry-off of dissipation to the processor heat sink.
In the mid-term, the Athlon64 will be AMD's entry-level and mainstream product. Only the 3200+ was available for the launch in September, although a 3000+ was also recently delivered. It's intriguing that both processors work at precisely 2.0 GHz; the only difference is the size of the L2 cache: 1 MB for the 3200+ and 512 kB for 3000+.
1 MB of L2 cache makes up more than half of the almost 106 million transistors on the Athlon64. That means that at a realistic yield of 40-50%, more than one in two dies will have a transistor defect. Ideally, and provided they are in a disconnectable area within the L2 cache, these dies (with reparable defects) will simply produce an Athlon64 3000+.
In practice, the problems lie not only in the area of the L2 cache. However, AMD is in a position to use the process to offer a cheaper Athlon64 and to minimize rejects. A choice must be made in any case if the aim is to appeal to as many different customer segments with the products to match - the Mobile Athlon64 is another example.
At present the advantage of the 64 bit Athlon is in its efficient memory management comprised of its large L2 cache and an integrated memory controller. In contrast to conventional solutions in which the memory controller is on the motherboard, slower data paths are dispensed with entirely on the Athlon64; the processor can communicate directly with the main memory, while the memory controller continues to work at full processor speed.
This high degree of integration makes the Athlon64 larger and thus pricier than the AthlonXP. Whether a 64 bit processor (3200+) is worth the $400 (U.S.) or €400 is not yet an issue of 64 bit support in home and office use, since 64 bit addressing for more than 4 GB only makes sense if this can be reasonably realized. These days, three DIMMs would be required in addition (2x 2 GB and another module), which poses problems for the Athlon64 and its platform: the more memory modules, the more the memory's working speed has to be reined in. These days, a speed of 200 MHz (DDR400) is attainable with just one DIMM.
The months ahead won't produce that much in the way of 64 bit software in any case, leaving these applications the preserve of the professional segment for now (Windows 2003 Server 64 bit Edition).
That leaves us with high performance under normal conditions (Windows 2000 or Windows XP and 32 bit software), substantial performance gains from overclocking and an interesting feature called Cool & Quiet that finally enables energy management in desktop PCs to mirror that found in notebook processors. Depending on load, the processor speed is regulated in several stages between 800 MHz and 2.0 GHz in order to lower power consumption during periods of inactivity and substantially reduce cooling requirements.
This species of energy management was long overdue in our opinion, yet the support provided by the motherboard makers is still amazingly lacking.
The Athlon64 feels at home here: Socket 754. The dimensions match those of the Socket 940, only fewer pins are required because it controls just one DDR memory channel instead of two.
|Fast||No 64 bit software|
|Modern architecture||Pretty pricey|
|Good energy management with Cool & Quiet|