Rialto debuts

X800 XL AGP and X850 XT PE AGP

Both cards use ducted coolers of similar size and shape

The X800 XL AGP is even longer than the 9800 PRO 256MB

The key ingredient in the RADEON X800 XL’s transition from PCI Express to AGP is ATI’s Rialto bridge chip. Like NVIDIA’s high speed interconnect chip (HSI), Rialto acts as a translator, converting PCI Express signals into AGP. Without the Rialto chip in place, the graphics card wouldn’t be able to “talk” with the North Bridge of the system chipset.

ATI has experienced multiple delays with Rialto, which was originally expected to debut with the X700 last fall (to the best of our knowledge, X600 and X300 were always intended to be PCI-E parts only), but when the X700’s RV410 graphics core was ready and Rialto wasn’t, ATI was forced to focus exclusively on the mainstream PCI-E market, while NVIDIA enjoyed sales of both PCI-E and AGP GeForce 6600 cards. Fortunately for ATI, Rialto is here now and Rialto-equipped versions of the X700 and X800 XL for AGP are now shipping (it’s important to note that the X850 series of AGP cards is an AGP native solution, Rialto isn’t used).

On the PowerColor X800 XL AGP board, the Rialto chip is located on the underside of the card, to the right of R430 when the card is flipped over. A pink thermal pad protects resistors on Rialto’s packaging from being accidentally knocked off by the end user, while the chip itself requires no cooling. In operation, Rialto does run pretty warm, but not nearly as hot as NVIDIA’s HSI chip, which requires a large aluminum heatsink and still gets pretty toasty, nor does it run as hot as Intel’s ICH6R South Bridge, but we still wouldn’t be surprised if some enthusiasts mount a small heatsink on the chip for better cooling (a RAMsink would be a good candidate). We would definitely recommend it if you plan on overclocking.

PowerColor logo up close

Another shot of the AGP cards

Rialto bridge chip

Not much is known about Rialto, as ATI has been pretty mum on details. For example early rumors indicated that Rialto could convert PCI-E signals into AGP, but couldn’t work in the other direction. If this report is true it wouldn’t impact ATI significantly in any case, as their recent graphics releases clearly indicate that they’re focused on the PCI Express interface anyway (keep in mind that the three ATI AGP cards that were announced back in February were the first AGP releases from ATI since the X800 family was launched in April of last year).

Finally, clock speeds carry over unchanged to the X800 XL AGP, ATI’s reference specifications call for the same 400MHz core/500MHz memory as PCI-E cards (although most board partners actually clock their boards at 398MHz on the core/492MHz memory, the performance difference is indistinguishable).