The Boards
Radeon X1900 XTX
Clearly deeming that their products haven't quite got enough X's in them, ATI have decided to add another in order to denote the very highest that their range, currently, has to offer with the X1900 XTX. It's said that this suffix has been chosen instead of the "Platinum Edition" moniker in order to circumvent the negative connotations over the availability of the parts associated with the Platinum Edition name.
With X1800 and X1900 having both the same IO properties, and despite R580's larger die size it does not need any more ground pins than was already facilitated on R520, the two chips at the heart of these boards are pin-for-pin compatible, so its not much a surprise that the boards are so similar. In fact, the boards are nigh on identical, in reference design, with the X1900 XTX board displaying a slightly higher revision number (50 as opposed to 10 for the early reference X1800 XT), which we wouldn't be surprised to see newer X1800's using now as well. The similarities between the X1800 and X1900 boards extend to all areas, which includes the heatsink design, which may displease a few - its curious that ATI haven't revisited this area yet as its not the quietest dual slot solution on the market, although the speeds, hence noise, is variable dependant on the core temperature.
One of the few differences between the boards is with the power circuitry as can be witnessed by the inclusion of an extra Pulse SMT power bead inductor towards the back of the X1900 XTX board, although the X1800 board shows the design was already there to facilitate it. With X1900 XTX operating at slightly higher clock frequencies for both the core and memory, and having a larger die size, it's no surprise that it will take up more power.
Removing the heatsink exposes the memory, which, as we'd expect, is in the same layout as X1800. One difference to note, though, is that the X1900 XTX board here is furnished not with 1.2ns memory but 1.1ns Samsung RAM. 1.2ns memory is rated for 800MHz operation (833Mhz if you take the timing literally), which should be enough to facilitate X1900 XTX's 775MHz memory clock speeds; 1.1ns is rated for operations up to 900MHz, which leaves a reasonable level of headroom left for the XTX boards, which may come in handy for overclocking. The RAM chips are, again, the newer 136 BGA packages, with 512Mb density, meaning that 8 chips facilitates the 512MB of local framebuffer on the XTX board.
Although this is an "ATI board" (note, the board marks it as "Made in China" indicating that this is actually a production board, as ATI's early reference samples are often built at their facility next to their headquarters in Canada) we suspect that, as has been the trend for high end boards over the last few years, all vendors will be using the same PCB design, and possibly even manufacturer, so we expect to see little variation with the options on the boards, or even the heatsink in many cases. With this in mind the outputs of the X1900 XTX board makes maximum use of Avivo's output options, facilitating two dual-link DVI-I outputs. Also, nestled under the heatsink is ATI's Rage Theater chip, which facilitates video input capabilities to go alongside the Xilleon based TV-Output capabilities.
Given that these 90nm based chips are getting very large and running very high clock speeds, ATI have recently started a power management scheme whereby they drop voltages and clockspeeds of the chip and memory when its not running 3D scenes. The reduction with X1900 XTX is a little more substantial than was the case with X1800 XT, with the core speed dropping from 650MHz to 500MHz, and the memory dropping from 775MHz to 600MHz. It appears, though, that ATI's activation for full clocks are based on D3D activity in fullscreen, such that windowed applications may still run at the 2D speeds.
Something of note is that we, inadvertently, got to experience an overheating scenario by failing to plug the fan back in after taking a look at the board. While we were unaware of the issue, the PC booted up fine and continued to operate in 2D mode for several minutes; after a while Catalyst Control Center issued a warning, with the PC bleeping, saying that the graphics chip was getting too hot, and then a little after that sent a signal to power down the PC cleanly. When the fan was plugged back in and the PC re-powered everything operated as normal. Although this may be quite commonplace now, its only been in the last few years that temperature sensors were implemented within high end graphics chips and its good to note that the hardware and software failsafe mechanisms are in place such that boards of this expense aren't necessarily going to grenade themselves should an issue such as a simple fan failure crop up.
