Review AMD announced the dual-core Athlon 64 X2 on 22 April. The chip won't ship until June, when it will be formally launched. Until then, all we have to go on is the pre-release technical preview kit AMD has been hawking of late, writes Leo Waldock.
It's not a fully fledged Athlon 64 X2-based PC but an Asus A8N SLi Deluxe mobo fitted with 1GB of Corsair 3200XL Pro memory and an Athlon 64 X2 4800+.
There are four chips in the Athlon 64 X2 family, all of which share a number of features with each other and with single-core Athlon 64s. Athlon 64 X2 continues to use Socket 939; the fabrication process is 90nm using SOI (silicon on insulator); the 128-bit memory controller is compatible with PC1600, PC2100, PC2700 and PC3200 DDR, although you'd be barking mad to use anything but top-notch memory; and there's one bi-directional 1GHz Hyper Transport link. This gives an effective data bandwidth of 14.4GBps (8GBps x 1 HyperTransport link + 6.4GBps memory bandwidth). The X2 has 64KB of L1 instruction cache and 64KB of L1 data cache, just like Athlon 64.
The second core raises the transistor count to 233.2m, but thanks to the 90nm fabrication process the die size is only 199sq mm. Compare that to the 130nm Athlon 64 4000+ and Athlon 64 FX-55 which have cores that use 105.9m transistors but which have an area of 193sq mm and you'll see what an effective die-shrink can bring to the party.
The Athlon 64 X2 4800+ has a nominal operating voltage of 1.35-1.40V and a TDP (Thermal Design Power) of 110W which compares very favourably to the FX-55 at 104W and the 4000+ at 89W. Add in support for SSE 3 and a revised memory controller to help compatibility with a broader range of memory modules, and what you've effectively got is a pair of the new 'Venice' cores tied together with the dual Opteron crossbar.
The differences between the four models of X2 come down to the core speed and L2 cache, so the 4200+ runs at 2.2GHz with 512KB of L2 cache on each core, the 4400+ is 2.2GHz and 1MB, the 4600+ jumps to 2.4GHz with 512KB cache, and the 4800+ is the daddy at 2.4GHz with a full 1MB of L2 cache on each core. This allows AMD to continue its desktop numbering series seamlessly from the Athlon 64 4000+, but the pricing takes a big hike. Official AMD pricing per chip, which is in US dollars and for a tray of 1,000 processors is as follows: 4200+, $537; _4400+, $581; _4600+, $803; _and 4800+, $1001.
Working from those figures we estimate that the X2 will sell in the UK including VAT at these prices: 4200+, £375_; 4400+, £400_; 4600+, £560; and _4800+, £700.
A few points jump off the page here. First, the gap between 4200+ and 4400+ is so close that you wouldn't bother with the 4200+. Second, the price gap between the 4600+ and 4800+ is very high for a bit of extra L2 cache. Third, the dollar price for the 4800+ has surely been chosen to dissuade customers from buying it. $999 looks steep but $1001, even though it's only $2 more, looks enormous.
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