The 760 chipset

The AMD-760 chipset

AMD's 760 chipset consists of two new chips: the 761 Northbridge and the 766 Southbridge. As we mentioned before, with 760, the system bus speed has been raised to 266MHz, providing 33% more bandwidth than previous Athlon chipsets.

In addition, 760 is fully compatible with existing 200MHz Athlon and Duron processors. Production motherboards should be able to automatically detect the bus speed supported by the processor without any input from the end user. Unfortunately, this wasn't the case for our 760 motherboard (which was one of AMD's reference motherboards).

Another important performance feature is 760's full support of PC1600 (for 200MHz processors) and PC2100 (for 266MHz processors) DDR SDRAM memory. In fact, the 760 chipset supports up to 4GB of memory maximum. Like the 750 chipset, the memory bus and system bus operate synchronously.

PC1600 DDR SDRAM provides the same theoretical peak memory bandwidth as PC800 RDRAM, 1.6GB/sec (50% greater than PC133). PC2100 DDR SDRAM is even faster, at up to 2.1GB/sec (100% greater than PC133). If a motherboard manufacturer chooses, both PC133 SDRAM and DDR SDRAM can be supported on the same motherboard, but interfaces for both DDR memory and PC133 will have to be present on the design. All DDR SDRAM controllers are backwards compatible with conventional SDRAM.

Just like older 750 and VIA KT133 chipsets, the 761 Northbridge and 766 Southbridge are connected via the PCI bus which now supports up to seven PCI master devices on the 760 chipset (up from six on 750). If a motherboard manufacturer chooses, the 766 Southbridge can be replaced by VIA's 686B chip. AMD's 766 Southbridge supports up to four USB 1.1 devices, as well as ATA/100.

Despite the launch of 760, AMD has no plans to become a serious player in the desktop segment of the chipset market. Like their 750 chipset last year, AMD plans to use 760 as a tool to guide the PC market in the direction they see fit. Just like 750, the torch will eventually be passed on to traditional chipset makers such as ALi, VIA, and SiS.

Next year a multiprocessor version of the 760 chipset will be introduced, future chipsets may even support AMD's Lightning Data Transport technology.

The DDR module

As we briefly noted above, DDR SDRAM isn't physically compatible with PC133 SDRAM. While DDR modules are the same size as conventional PC133 modules, DDR requires 184 pins while PC133 SDRAM requires 168 pins. Here's a picture of the CAS 2.5 PC2100 DIMM we used for our tests:

128MB PC2100 DDR SDRAM