ATI Radeon 5800 Detailed

AMD slides detailing the new "Evergreen" architecture.

The previous post about the new Radeon 5800 series already detailed that AMD might have glued two RV770 SIMD blocks together, this seems true although with some caveats detailed further below.


The most interesting tidbits here are CRC support and the ability to down clock the memory clock without screen flicker. The latter helps achieve the low idle power consumption of 27W that AMD promises for these cards.


Small L2 caches, 512KiB total(apparently, AMD had eight L2 caches in the RV770, so it may double). Remember that these cores have a huge number of registers which help make up for the smaller caches: the RV770 had 2.5MiB of register space.


GPGPU will go better in the RV870 core than it did in the RV770: these numbers are even more interesting than the GT200.
Although AMD only provides 160GB/s to the framebuffer, the new chip has a relatively big 64KiB Global Data Share memory that is unique to AMD's architecture and was already present in the RV770 chip but is now four times bigger. This might be one of the reasons AMD managed to keep bandwidth requirements to the framebuffer low, as this memory helps keep communication far from the framebuffer, something that Nvidia can't do as it only has the Local Data Share memory. Speaking of which, AMD now has double the amount of Local Data Shares compared to what Nvidia delivers in the GT200 chip per multiprocessor: 32KiB. This equals to a total of 640KiB of Local data share, while Nvidia only has 384KiB right now. It seems AMD was holding back before, as it has now delivered a very competent GPGPU chip just as OpenCL compilers start to tip up.
The new chip seems to have also gained IEEE754-2008 floating point standard compliance when calculating 32-bit vales(before only 64-bit was compliant), although I won't still guarantee you that. At least not until I get my hands on proper documentation of the architecture or a card to run some tests.


Market placement: "Cypress", or RV870, the Radeon 5800 series cards will range from $249 to $349 and "Juniper" will be delivered to the sub-$200 market.

Reviews for the new card are expected this week.