AMD Opteron Coverage - Part 4: Desktop Performance

Predicting Athlon 64 Performance?

One thing you have to keep in mind while looking at the performance comparisons we're about to show you is that the Opteron is no Xeon in that there are some significant performance differences between the Opteron and the Athlon 64.

As a quick recap of the architectural changes, here's what makes an Opteron different:

The pincount of the Opteron alone should give you an indication that it is a noticeably different chip than the Athlon 64. While the desktop Athlon 64 weighs in with a plentiful 754 pins, the Opteron has no less than 940 pins. What are the additional pins being used for?

While the desktop Athlon 64 only has a single Hyper Transport link, each Opteron CPU has three links - two for connecting to other processors and one for connecting to I/O bridges (e.g. South Bridge, PCI-X bridge, etc…).

The next difference between the Athlon 64 and the Opteron is that the Opteron features a 144-bit wide DDR memory interface, in comparison to the Athlon 64's 64-bit DDR memory controller. The 144-bit wide memory bus is over twice as wide as the Athlon's, but offers basically twice the memory bandwidth. The additional bits are parity bits, as the Opteron's memory controller only supports ECC memory.

We used Corsair DIMMs in our tests

Although the Athlon 64 and Opteron both feature a 128KB L1 cache (64KB instruction cache, 64KB data cache), the Athlon 64 will be available in both large and small L2 cache sizes (1MB and 256 respectively) while the Opteron will stick with 1MB.

To sum things up, the main difference you have to worry about is that with the Athlon 64, you'll have essentially half the memory bandwidth at your disposal; so in memory bandwidth intensive applications, expect Athlon 64 performance to be lower at a given clock speed than what we can show you here on an Opteron.

Also keep in mind that the motherboards we're testing with are not tuned for extracting every last ounce of performance, they are setup for stable, reliable, 24/7 operation. Overall performance will be higher on nForce3 Pro boards aimed at the enthusiast market as well as Athlon 64 motherboards once the chip is released.