ATI CrossFire Xpress 3200

First of all I would like to point out that new AMD processors intended for Socket AM2 mainboards do not feature any innovations that should require new sets of core logic. In other words, the new CPUs use the same HyperTransport interface with 1GHz frequency and 16bit width in each direction to connect the CPU and the chipset. As for the DDR2 SDRAM support that has been introduced in the Socket AM2 platforms, it has nothing to do with the chipset, because the memory controller is built into the processor. It means that the manufacturers can still use the old chipsets to design new mainboards for the recently announced Socket AM2 CPUs.

Nevertheless, both ?ATI and Nvidia ?decided to tie the innovations in the core logic solutions to the recent launch of the first Socket AM2 processors. As a result, most mainboards for Athlon 64 processors with DDR2 SDRAM support will be based on the new chipset models.

Although the ATI core logic for Socket AM2 platform is called CrossFire Xpress 3200, the name that has already been used before, the Canadian manufacturer introduced a new SB600 South Bridge for this chipset. I have to stress that this is a significant improvement of the previous chipset solution, because the previous-generation ATI South Bridges have received a lot of criticism for the quality of some busses and protocols implementation. Moreover, ULi Company that has recently been acquires by ATI’s main rival, Nvidia Corporation, can no longer supply their South Bridge chips for CrossFire Xpress 3200 based mainboards. Therefore, looks like SB600 South Bridge chip is coming in the right time.

As for the features of this microchip, they have changed a lot since the days of SB450. The new South Bridge features an updated Serial ATA and USB 2.0 controller. As a result, firstly, the new implementation of CrossFire Xpress 3200 is free from earlier problems with High Speed USB bus speed and has more USB 2.0 ports now: the total of 10. Secondly, the new ATI chipset has fully-fledged Serial ATA II support, i.e. higher interface bandwidth of 3Gbit/s and NCQ support. As for the RAID functionality, the new South Bridge supports array 0, 1 and 0+1, and later on should also acquire RAID array 5 support, too. Note that the number of Serial ATA II ports supported by the chipset remained the same and equals 4, although there is a tendency toward getting support for more ports, of course.

Speaking of other features offered by the new ATI SB600 South Bridge I would like to point out that it retained the High Definition Audio (Azalia) support.

The networking functions of the ATI SB600 chip have been removed in order to encourage mainboard developers to use fast gigabit PCI Express x1 network controllers on their platforms. By the way, Intel also uses the same tactics in their LGA775 solutions, so no wonder that ATI resorted to it, too.

Just like in Intel’s South Bridges, ATI reduced the number of supports Parallel ATA ports. SB600 features only one port like that, i.e. it allows connecting maximum two Parallel ATA-133 devices.

SB600 South Bridge retained the traditional hardware monitoring controller that is absent by other manufacturers?solutions and is usually implemented as a separate chip on the mainboard PCB.

The ATI SB600 South Bridge is connected with the chipset North Bridge via the A-Link Xpress II bus that boasts the same architectural design as PCI Express x4. As a result, the maximum bandwidth of the bus between the North and the South Bridge of the CrossFire Xpress 3200 chipset is 2GB/s. You should understand that this connection is no bottleneck here, because all the hi-speed PCI Express busses are implemented in the RD580 North Bridge of the chipset.

In other words, it is the chipset North Bridge that is responsible for two PCI Express x16 busses for CrossFire configurations as well as PCI Express x1 bus of the CrossFire Xpress 3200 chipset.