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.
Put an Athlon 64 X2 on the bench next to a regular Athlon 64 and you won't be able to tell the two processors apart as all of the changes are internal. As with the dual-core Opteron you should be able to upgrade your existing Athlon 64 PC after a BIOS update - there's no need to change your motherboard. Indeed, with the 110W power rating we would hope that you would be able to continue using your existing heatsink/fan unit.
We built the AMD hardware into a test system by adding an Areca 1220 PCI Express RAID card and four Western Digital Raptor WD740 hard drives in a RAID 5 array, along with an Antec True550P EPS12V 550W power supply that we had on the test bench and which happened to be exactly the model that AMD recommends. We let the side down a bit by installing an Asus N6600GT graphics card as that's what we happened to have to hand. Yes, a GeForce 6800 Ultra or Radeon X850 PE would have been nice but as you'll see it wouldn't have affected our test results one little bit. So that we at least looked like we were trying we ran the Asus N6600GT at 550MHz core and 1100MHz memory on Detonator 71.84 drivers.
We started by running SYSmark 2004 on the X2 4800+, and we immediately hit a problem. We were using Windows XP Pro Service Pack 2, and the Office part of SYSmark wouldn't run as the No Execute protection kept kicking in. This occurred a number of times until we disabled both of the integrated LANs and installed an Intel Pro/100 NIC and then switched from Nvidia's firewall to the Windows firewall. This is particularly odd as you inherently run SYSmark 2004 with networking disabled so you wouldn't have thought that it would much matter what the settings were but there we have it.
Once we'd cured the problem, the X2 4800+ pumped out a startling score of 281 in SYSmark 2004, while the results in 3DMark05 and Doom 3 were much as you would expect.
We removed the X2 4800+ and replaced it with an Athlon 64 FX-53 which runs at the same 2.4GHz and also has 1MB of L2 cache, so we were able to carry out a direct back-to-back comparison between single-core and dual-core processors and the results were telling. There was no change at all in 3DMark05 and Doom 3, but the SYSmark 2004 score dropped from 281 to 214 marks. Most of the change was in the Internet Content Creation part of the test where the software runs scripts in Discreet 3D Studio Max, Adobe Photoshop, Macromedia Dreamweaver and the like.
To put that score of 281 for the X2 4800+ into context, the Armari that we used for our dual-core Opteron feature had a pair of Opteron 875s running at 2.2GHz and it scored 254 marks. The X2 4800+ has a 200MHz core-speed advantage, uses faster memory than the Opteron system and has a very fast hard disk array but even so it was a real surprise to see how well it performed in SYSmark.
The reason that X2 4800+ shows a 50 per cent improvement in the ICC part of SYSmark over the FX-53 is due to the multi-threaded nature of the applications, and the reason that it shows no benefit in gaming is that most games don't yet use multiple threads.
You might feel that the X2 4800+ looks very pretty on paper, but if you have no yearn for the digital lifestyle it may look like an expensive luxury. We wondered about that so we ran the same real world usability test that we performed on the Pentium Extreme Edition and Armari dual 875. We loaded up Bit Defender anti-virus and iTunes, and set the two applications running. While Bit Defender ran a full system virus scan we started to encode three albums of MP3 files to AAC format with iTunes, and then we started to play Doom 3.
With the FX-53 processor in our test system Bit Defender pegged the CPU at 100 per usage, and after we started iTunes encoding, Doom 3 simply refused to open, let alone play.
It was a completely different story with the X2 4800+ which could split the workload between the two cores, so running iTunes barely made an impression. With both iTunes and Bit Defender running we were able to play Doom 3 without any dropped frames, and although the processor was working very hard it was completely invisible to us.
So you see, there is a benefit to gamers from dual-core right now: you can run other applications while you're gaming without shedding game performance. Your favourite game won't get any faster until it's coded to run as more than one thread, but it won't slow down significantly if you want to run stuff in the background.
NV Monitor shows that the X2 4800+ was running at a mere 37&176;C and the Thermaltake heatsink was cool to the touch.__
There's no doubt that the Athlon 64 X2 4800+ is very impressive indeed. Combined with the nForce4 SLi chipset it has performance that is truly staggering, and the only possible source of disappointment is the price. That and perhaps the fact that we don't expect speed increases to come along thick and fast. We'd guess that 2.6GHz at the start of 2006 and 2.8GHz at the end of 2006 with a 3GHz version in 2007 is close to the mark. We're about to be hit by a wave of new technologies as 64-bit computing and virtualisation come to the desktop, and we can't wait to see what benefits they bring, but right now Athlon 64 X2 is at the top of our tech shopping list.
|AMD Athlon 64 X2 4800+|
|More info||The AMD multi-core site|