CrossFire Xpress 3200: Brief Review of the Capabilities

Although the CrossFire Xpress 3200 was developed from scratch in only eight months, the first revision of the RD580 chip was fully operable. ATI’s engineers took only 24 hours to make the new chipset absolutely stable.

The new North Bridge came out very small notwithstanding TMSC’s 0.11-micron tech process and 40 PCI Express lanes. Consisting of 22 million transistors, the die is only 39 square millimeters large:

This is considerably smaller than the die area of the nForce SPP 100 (C51D) North Bridge of the nForce4 SLI X16 chipset, which is manufactured on 0.09-micron tech process and supports only 20 PCI Express lanes. The ATI RD580 is in fact the smallest North Bridge on the market! Another advantage of the new chip is very low power consumption at only 8 watts. It means there will be no clumsy and noisy coolers on upcoming CrossFire Xpress 3200-based mainboards whereas some existing mainboards on the nForce4 SLI X16 are equipped with sophisticated cooling systems on heat pipes.

The CrossFire Xpress 3200 is omnivorous when it comes to South Bridges: any chip with PCI Express support will do. Four PCI Express lanes, forming the so-called Alink2 interface, are allotted in the RD580 for connection to the South Bridge. The total bandwidth of this interface is 2GB/s (1GB/s in each direction). This should be enough for the standard peripherals integrated into South Bridge chips.

We should note that ATI’s SB450/460 South Bridges and ULi’s M1573 chip fall short of today’s requirements as they do not support Serial ATA-II. So, we will most likely see an M1575 South Bridge from ULi on early off-the-shelf mainboards on the CrossFire Xpress 3200 chipset. This chip has fewer USB 2.0 ports than the nForce4 SLI (eight against ten) and doesn’t support Gigabit Ethernet, but it can work with HAD (High-Definition Audio) codecs, while Nvidia’s chipset cannot. The lack of Gigabit Ethernet is not a big problem as it can be solved by attaching any suitable single-die controller with PCI Express x1 interface to the North Bridge. For example, the Marvell Yukon 88E8053 can do. Later on, the new SB600 South Bridge from ATI is going to be the main companion to the RD580. This chip is expected to appear in the middle of this year.

To summarize this section, we want to offer you a table that compares the technical characteristics of the modern chipsets that support two complete PCI Express x16 slots:

?/td>	Nvidia nForce4 SLI X16 (AMD Edition)	ATI CrossFire Xpress 3200
Architecture	Dual-chip North bridge: nForce SPP 100 South Bridge: nForce4 SLI.	Dual-chip North Bridge: ATI RD580 South Bridge: ULi M1575*
Connection between bridges	HyperTransport (8GB/s)	PCI Express x4 (2GB/s)
HyperTransport support	16 bit / 1 GHz	16 bit / 1 GHz
PCI Express lines	38	40
Multi-GPU support	Yes, SLI North Bridge: 1 x PCI Express x16 South Bridge: 1 x PCI Express x16	Yes, CrossFire North Bridge: 2 x PCI Express x16
PCI support	Yes, 6 devices	Yes, 7 devices
USB 2.0 support	10 ports	8 ports
Serial ATA support	Yes Serial ATA-II, 3 Gbit/s	Yes Serial ATA-II, 3 Gbit/s
NCQ support	Yes	Yes
Serial ATA ports	4	4
Parallel ATA channels	2	2
RAID support	Yes, 0, 1, 0+1, 5, JBOD	Yes, 0, 1, 0+1, 5, JBOD
Ethernet support	Yes, 1 Gbit/s	Yes, 10/100 Mbit/s
Network security	Yes, Nvidia Active Armor	None
Audio support	AC?7, 8 channels	High Definition Audio (Azalia)

* - other bridges can be used : ATI SB450/460/600, ULi M1573.

So, the ATI CrossFire Xpress 3200 doesn’t yield to Nvidia nForce4 SLI X16 in terms of functionality (with a few allowances), but is far superior when it comes to the architectural concept we will dwell upon in the next section.