Unlike Intel, who has migrated to hub architecture, AMD is still utilizing the North/South bridge design. The AMD-761 system controller incorporates several enhancements to increase the rate of data flow across the entire system.

One of the most significant changes comes to the EV6 system bus, which has been running at 100MHz DDR since the Athlon's introduction. Now, with the 761, the system bus will transfer information at 133MHz DDR (266MHz effective). This increase in speed, coupled with the use of DDR2100 memory, will theoretically deliver 2.1GB/s peak data transfer. Will the difference be night and day, as with DDR video cards? It is doubtful, but the good news is that faster processors will deliver more compelling performance since the system bus will not serve as a bottleneck.

With this bus speed increase comes another interesting point. All of the Athlon processors up until now have run on a 100MHz bus, so moving to 133MHz means that clock multipliers have to be adjusted. Using an Athlon CPU (we'll use a 1GHz CPU as an example) on a DDR motherboard clocked for 133MHz operation would result in 1.33GHz operation – not good unless you are deliberately trying to fry your CPU. In order to take advantage of the extra bus speed, you will have to purchase a new processor with an adjusted multiplier, such as the 1.2GHz CPU that shipped with our sample and operated off a 9x multiplier.

Secondly, the 761 incorporates a brand new memory controller that offers support for DDR memory. Since the timings for this new memory technology are different, the memory interface is not backwards compatible with older PC133 modules. This issue is completely taken care of by the physical pin-out of the DDR memory module. As you can see below, the DDR module is completely different from the PC133 stick.

The 761 chipset supports an astounding 4GB of memory. To achieve this memory ceiling, four banks of registered 256-Mbit DIMM modules must be used. Unfortunately, when unbuffered DIMMs are being utilized, only two memory slots may be filled leaving the remaining slots empty. While our reference board shipped with four DIMM slots, we should expect to see many of the value (if there is such a thing) motherboards shipping with only two slots due to this limitation. Of course, memory-timing parameters are configurable in the BIOS, so tweakers and overclockers should have an entertaining time squeezing further performance from the already-blazing double data rate memory.