Cable-less Crossfire - P965 and the X1600XT - FastSilicon.com

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Cable-less Crossfire - P965 and the X1600XT

Article Index
Cable-less Crossfire - P965 and the X1600XT
Specifications
What You Get
Test Setup And Benchmarks
Conclusion

Page 3 of 5

Overview

The RV530 core in the Crucial Radeon X1600 XT is a 90nm chip featuring 157 million transistors operating at a core frequency of 587mhz. It features 12 pixel shader processors, 5 vertex shader processors, and a 128bit memory interface to it's 256mb of GDDR3 memory operating at a DDR clockrate of 1386MHz. It and it's lower end brethren (with the notable exception of the RV570 derivative x1950 cores) are unique in supporting cable-less Crossfire and eliminating the need of a specific "Master" card that contains ATI's Crossfire Compositing chip. Compositing chores are handled by the driver, and communications are handled by the PCI-Express bus instead.

The Crucial Radeon X1600 XT 256MB PCI Express is a value oriented graphics card, and it comes at a very value oriented price of $139, which isn't exactly going to break the bank even if you get two of them.

Inside the attractive outer box sleeve you will find your typical cardboard clamshell box. Along with the card itself, you get a DVI-to-VGA connector, an S-Video to Composite adapter and a Composite video cable, an S-Video to Component adapter, and an S-Video cable. Also you get a very basic but thorough Installation Guide, the ubiquitous copy of PowerDVD, and a rather ancient Catalyst 5.10 driver installation disc.

Looking at the card itself, you do notice that Crucial didn't deviate from ATI's reference design at all, and apart from the Crucial decal on the modestly elaborate copper heat sink, there's little to differentiate this card other offerings. Indeed, this card is practically identical visually to Sapphire's version, apart from the different decal. These cards are single slot solutions thankfully, and we found them to be unobtrusive from an audible standpoint though not totally silent. The back plate features the standard VGA, DVI, and S-Video connectors we've all come to know and love as well.

Installation was basically hassle free. The latest edition of the PX1 BIOS specifically adds support for ATI Crossfire, a fact made glaringly obvious by the modification made to the PX1's "Splash Screen" upon booting the system up. The uppermost PCI-E x16 slot is the primary slot on the PX1, with the second physical PCI-E x16 slot only supporting x4 communications and thus the slot used for a secondary card in a Crossfire configuration.

Driver installation was also hassle free, though we certainly didn't install the drivers that came with the card, ATI's Catalyst 5.10 drivers, as these are well over 3 months old and don't properly support Crossfire in this setup. We ended up using ATI's newest 7.1 Catalyst Driver Suite instead. Enabling Crossfire support is as simple as checking a box in the suite's Crossfire section. We could have over clocked the cards, but decided against it as it was beyond the scope of what we intended to evaluate here. The PX1, although a stable and serviceable board with everything stock has given us a fair share of grief when tweaking. With this being the first Crossfire enabled BIOS revision available we didn't want to push our luck.

Before we go on, let's take a little deeper look into the P965 chipset, so we can understand exactly what is going when it comes to implementing Crossfire support.

On the Intel platform, the 975x chipset has been the chipset of choice by and large for supporting ATI's Crossfire barring ATI's own chipsets of course, which are slated to be a scarce commodity going forward due to the AMD/ATI merger. As you can see from the block diagram below the 975x chipset allows the MCH's 16 PCI-Express lanes to be split into two sets of 8. Though this sounds a bit cheap on the surface an x8 slot does have adequate bandwidth to feed a modern graphics card

Looking at the P965 block diagram, things seem mostly similar, but you will note there is no indication that the MCH's 16 PCI-Express lanes can be split. Instead, to implement a secondary PCI-Express video slot on a P965 platform board one has to use at most 4 of the PCI Express lanes off of the ICH8 chip. The real limitation here is "potentially" saturating the DMI communications interface between the ICH8 and the P965 MCH, as this is the pipeline that all of the ICH8's functions use for communications.

Whether this is an issue, is sort of the whole point of this article, so let's move forward. With all the groundwork in place, let's proceed to our test setup, and take a look at some benchmarks and see how these cards scale.

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