Let the Quad Core War Begin

Original Article Date: 2007-09-17

AMD launched their long awaited "Barcelona" quad-core Opteron CPU just a week ago. Hyped as the world's first "true" quad-core (four CPUs on a single die of silicon), AMD claim that this design outstrips in performance the pseudo quad-core design of Intel's "Clovertown" CPU.

The war already began last month with Intel slashing the cost of their Clovertown quad-core CPUs, in an attempt, I believe, to spoil AMD's Barcelona launch. It's hard to believe Intel are making any profit over the sale of these CPUs. Either that, or they were making a small fortune in selling the dual-core Woodcrest models, since the pricing of the quad-cores was dropped to within 20% of the equivalent clock-speed dual-cores.

So this price drop may be temporary. But then again, it may be permanent. Intel has already released the Core CPU built on the more efficient 45nm (nanometer) process technology (look out for next month's article "What's in a Nanometer?"), and this 45nm technology is expected to appear on the Xeon line of processors in late Q4 '07. I see Intel lining up AMD for a one-two punch in this regard. Since, with AMD having only just gone over to 65nm technology, and Intel commanding ten times the market capitalization of their smaller competitor, AMD are looking vulnerable. But then one thing that AMD have shown us in the past is that, despite the odds of being the underdog for more than a decade, they are a survivor.

Barcelona is a chance for AMD to play catch-up once more. It's a critical launch for AMD. But does the hype live up to real-world performance advantage?

Inside "Barcelona"

Barcelona's four CPU cores on a single slab of silicon - a world first 

The big headline about AMD's new chip is the fact that it's the world's first true quad core CPU. With all four cores etched onto the same piece of silicon, this is expected to bring benefits in terms of reduced latencies and wider data bandwidths between the cores and the multiple caches and system memory.

Compare this with Intel's "Clovertown" quad-core CPU. Intel's chip is in fact two dual-core CPUs wired together. So AMD's claim of being the world's first true quad core CPU is, indeed valid.

Other differences with Clovertown lay in Barcelona's incorporating the memory controller (or "northbridge") on-chip, instead of on the motherboard. This tradition began way back in 2003 with the first generation of Opteron processors, and has the advantage of reducing latencies between CPU and system RAM. However, it does have a price, and that is one of real estate. As can be seen on the picture to the right, the memory controller takes up significant and precious space on the chip. And this is perhaps one of the reasons why they had to reduce cache size.

Briefly, a cache is a small amount of very high speed memory that stores data that is frequently used and on a repeat basis by the CPU. By storing such data in this highly local and lightning fast memory, the CPU does not have to make comparatively long trips to the main system RAM for most of its commands, thus improving performance significantly. Typically, CPUs have an L1 and L2 cache. The tiny L1 execution cache (in Barcelona's case, 64K) sits inside each core, and stores the most frequently used CPU data.

The headline cache figure you see with CPUs is the L2 cache - in Barcelona's case 512K per core (i.e. 4x512K = 2MB). This L2 cache size might not sound like as much as Clovertown's giant 8MB (2x4MB) caches, and generally speaking, the bigger the cache, the better the performance. But AMD claim that their dedicated small cache operates more efficiently than the shared cache of Clovertown.

Furthermore, AMD have broken with tradition in putting an L3 cache on-chip - 2MB in size. Typically a CPU either has no L3 cache at all, or it is placed on the mainboard, close to the CPU. By moving the L3 cache to the CPU die itself, AMD believe this will provide more optimization of cached-data, and more efficient and faster CPU operation.

AMD claim a number of other innovations, such as Optimized Virtualization. Virtualization is the ability of a CPU to be able to run more than one operating system simultaneously, using special software, and is becoming increasingly popular as hardware power continues to outstrip software need. With virtualization, system admins can run a web server, a mail server, and a file server, for instance, all on the same box, running simultaneously, but on totally separate instances of, say, Windows 2003, or Redhat Linux. By providing optimization code for virtualization, AMD are acknowledging and looking to gain more of an advantage in this increasingly popular method of maximizing server hardware utilization.

Squaring Up with Intel's Clovertown

The following table shows the full list of quad-core CPUs available from AMD as of the launch date:

As you will likely notice, there is not a huge amount of choice available at this time, with clock speeds falling within the 1.7-2.0GHz range. This was somewhat disappointing, as I'd hoped that AMD would be sporting the 2.6GHz model that AMD had quoted in a number of their own benchmarks. This higher speed model would have been necessary to compete directly with the fastest Intel Clovertown model, the Xeon 5365 operating at 3.0GHz clock speed. AMD have promised that higher speed CPUs will become available over the next few months. Let's hope they live up to their promise.

How does this line-up compare in terms of price and performance with Intel's quad-core Clovertown? Well, there is no comparison in the 4/8-Socket HPC (High-Performance Computing) space, where AMD dominate. AMD's launch of quad-core 4-way and 8-way supported CPUs will continue to enhance the affordability and performance of this growing market segment, which was once the preserve of Cray and IBM supercomputers. 

But in the much larger 2-socket segment, AMD must clearly demonstrate their ability to compete with Intel's dominant Clovertown Xeon CPUs.

Early benchmarks in a number of online test sites such as Tom's Hardware Guide and Anandtech suggest that in some tests AMD's Barcelona significantly outperforms Intel's Clovertown at the same price point, while in others, it lags. The current consensus? They're about even.

Sadly, AMD, really needed to demonstrate that their inclusion of four cores on a single die (instead of Clovertown's gluing of two dual-core dies together) would have resulted in a significant and commanding lead in performance over Intel's Clovertown. Early benchmarks indicate that this has not happened, and so I believe that Intel's dominance of the 2-socket CPU market is likely to continue.

That said, many workstation customers of mine specifically prefer Opteron over Xeon, citing better stability and software compatibility. Having quad-core CPUs to choose from for future purchases (and also for possible upgrades to existing dual-core workstations), and knowing that these new CPUs are at least on a par with Intel's equivalent, is great news for AMD-loyal customers.

Upgrading from Dual Core to Quad Core is Simplicity Itself

An important advance has been that AMD have been able to double the number of cores on each die, without increasing the power consumption of the chip. Due to excellent future planning from AMD, the Opteron Socket F design has complete forward compatibility built into it, enabling system admins and individual users to double the computing power their existing server and workstations with just a single CPU exchange and a BIOS update. No new heatsinks, system fans or power supplies are required.

Combined with our offer to buy back your existing dual core CPUs at the time you buy your quad core Barcelona CPUs, you will find that doubling your system's processing power can be a lot cheaper than you could imagine!

Barcelona and the Future of AMD

The long awaited launch of Barcelona has enabled AMD to get back in the game again. They will continue to dominate the 4/8-socket High Performance market. But because of apparent relative parity in performance with Intel's quad-core chip in the 2-socket mainstream server and workstation arena, I expect that AMD will continue to play second fiddle to their bigger brother, which has had quad-core chips available since January of this year.

And what AMD need right now, more than anything, is a good shot in the arm. I don't think this happened with their quad-core launch. This is sad, because if AMD don't claw back some market share, and get some return on all the investment they have put into developing Barcelona and its 65nm technology, their mounting losses could continue, leading them into even stormier waters financially. The last thing that I, and I'm sure you, would want to see, is the loss of a major competitor to Intel.

It is ironic that we have AMD to thank for the tremendous processors we have from Intel today. Three years ago, the server CPUs Intel were producing were lackluster, workmanlike, average at best. But AMD's far superior Opteron kicked them out of their complacency, and made them fight back.

If AMD go under because of a potential failure of Barcelona to pull them out of their financial difficulties, then we have a monopolistic Intel future to look forward to once more, and the technological stagnation and poor value that always results from monopoly, accompanying it. And I don't know about you, but that prospect simply makes me shudder.

Let's continue to wish for competitive times in the CPU marketplace.

Best regards,

Ben Ranson
Chief Systems Engineer