ATI’s Radeon X1800 XT CrossFire could deliver near-double results in selected synthetic tests and strong scaling in many games, but it was not a universal 2× upgrade. It required a dedicated CrossFire Edition master card, a compatible X1800 slave, a certified dual-slot motherboard and an external cable; performance varied by game, while system power and cost were substantial for the period.
What components did an X1800 XT CrossFire system require?
ATI’s setup paired a dedicated Radeon X1800 CrossFire Edition card (the master) with a compatible standard Radeon X1800-family card (the slave). The master contained the compositing engine and a VHDCI connector. The system also needed an ATI-certified CrossFire motherboard with two PCI Express x16 slots and the external interconnect cable supplied with the CrossFire Edition card. ATI’s official X1800 CrossFire guide describes the required combination.
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- Radeon X1800 CrossFire Edition master card
- Compatible Radeon X1800-family slave card
- Certified motherboard with two PCI Express x16 slots
- Compatible external interconnect cable
This is a specific dual-card configuration, not simply two ordinary X1800 XT cards. For a retro build, verify the exact master-card model, cable, board certification and slot arrangement before buying; period documentation does not establish present-day availability or compatibility with current systems.
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How did CrossFire work, and how was it enabled?
The slave sent its rendered output through the external cable to the master, which combined the images and sent the result to the display. The master belonged in the primary PCI Express slot. ATI noted that some systems required both PCIe slots to be enabled in motherboard firmware settings. CrossFire also had to be enabled in Catalyst Control Center.
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- Install the CrossFire Edition master in the primary PCI Express slot and the compatible slave in the second slot.
- Connect the cards with the compatible external interconnect cable.
- Check motherboard firmware settings and enable both PCI Express slots if required.
- Enable CrossFire in Catalyst Control Center.
ATI’s guide describes SuperTiling, Scissor Mode and Alternate Frame Rendering as performance-oriented rendering methods, with the driver selecting among modes. Super Anti-aliasing was a quality-oriented option. When CrossFire was active, display devices other than the one used by CrossFire were disabled. ATI warned that the cards should not touch, to reduce the risk of overheating.
How much faster was X1800 XT CrossFire?
There was no single scaling result that applied to every game. ATI said performance enhancements depended on the application or game, and advertised gains of up to 100%. That figure is a vendor-stated ceiling, not a typical or guaranteed game result.
Contemporary reviews found the XT pairing competitive, but its standing shifted across test suites and titles. PC Perspective’s December 20, 2005 review found it performed well in most of the games tested, while GeForce 7800 GTX 512 SLI more often led and won some comparisons. AnandTech’s December 20, 2005 conclusion placed X1800 XT CrossFire between GeForce 7800 GTX SLI and GeForce 7800 GTX 512 SLI in many cases. These are historical results from each publication’s own test systems, games and settings—not a universal ranking.
SimHQ’s 2006 3DMark05 checks illustrate the best-case appeal of parallel rendering, but only for those synthetic tests. At the program’s default 1024×768 resolution, it recorded:
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- OC mode (GPU Tweak III): up to 3330 MHz (Boost Clock)/up to 2760 MHz (Game Clock) Default mode: up to 3310 MHz (Boost Clock)/up to 2740 MHz (Game Clock)
- 2.5-slot design allows for greater build compatibility while maintaining cooling performance
- Dual-ball fan bearings last up to twice as long as standard conventional sleeve bearings designs
- 0dB technology lets you enjoy light gaming in relative silence
- Dual BIOS switch lets you toggle between Quiet and Performance BIOS profiles
| Test | One Radeon X1800 XT | X1800 XT CrossFire |
|---|---|---|
| Fill rate | 9,811 MT/s | 19,576 MT/s |
| Pixel shader test | 230 fps | 454 fps |
| Vertex shader test | 57.3 MV/s | 114 MV/s |
The near-doubling in these figures should not be projected onto games: application support and workload determine whether a second card helps.
Where did the configuration fall short?
Scaling depended on software. Some titles failed to benefit or could regress. AnandTech reported a pronounced performance problem in Black and White 2 and said its reviewers wanted better application detection and more per-game control. That exception matters alongside the favorable results: CrossFire’s theoretical capacity did not guarantee that a particular game would use it well.
There were also practical trade-offs. The external dongle was less convenient than the internal bridge used by NVIDIA’s competing setup, and AnandTech cited high system purchase cost and limited launch availability. The two cards occupied more space and required attention to airflow and clearance; ATI specifically cautioned against letting them touch.
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What did power consumption and cost mean in practice?
PC Perspective measured nearly 400 watts for its entire test computer, excluding the monitor, with the XT CrossFire system near the top of its comparison group and recording the highest idle power in that group. This was a whole-system measurement from a 2005 test—not power draw for the graphics cards alone, and not a modern PSU recommendation.
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- Memory Size: 20 GB
- Memory Interface: 320-bit DDR6
- Form Factor: 3 slot, ATX
- Output: 1 x HDMI, 2 x DisplayPort, 1 x USB-C
- PCI-Express 4.0
The cost was likewise a period concern: a buyer needed two graphics cards, a compatible motherboard and adequate system hardware. Historical reviews discuss launch-era pricing and availability, but they do not establish what working parts cost or whether suitable components are available now.
Is X1800 XT CrossFire worth considering for a retro build?
It is best understood as a historically interesting high-end configuration rather than a straightforward performance upgrade. Consider it when the goal is to reproduce or explore period multi-GPU gaming and the required parts are already available and verified. Before committing, check the exact master and slave models, cable compatibility, motherboard certification and slot layout, card spacing, power requirements, and driver and operating-system support for the games you intend to run.
Keep X1800 XL results separate from XT conclusions: PC Perspective found the XL pairing less compelling in its price/performance comparison, so it is not a substitute for evidence about the XT setup.
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