Advantages over Intel
As stated earlier, the Pentium D suffered from forcing data to move between cores along the same path that information came and went from the RAM and the chipset. With the advent of the Conroe, this problem was fixed by making the cores talk at full cache speed. Then Intel reverted again with the Kentsfield. The Kentsfield features two Conroe cores that can only talk via the FSB, the Achilles’ heel of the Pentium D. From the start, AMD’s chips have natively supported dual core with the assistance of a crossbar switch that ran at full processor frequency. Now with their attempt at a quad core system they have taken the Intel approach but improved upon it. They took their proven HyperTransport interface and connected it straight from one chip to the other. Now instead of 3 different, important items sharing an 8.5GB/s FSB, the two chips are talking straight to each other at 8.0GB/s, without sharing anything. If all four cores are utilized for the same project and they have to give and take from each other, such as running a 4-threaded video encode, this advantage could prove to be pivotal. Another advantage is that AMD has stated that 4x4 will be future proof for the native quad core chips that they plan on launching in Q2 of next year. Plugging two of those into a 4x4 system would give you 8 cores well before Intel has anything like that available. Right now, the use for 8 cores is pretty much nil - besides owning your friends at Folding@Home - but by Q2 07, who knows? These are the two advantages we came up with that 4x4 can have over Intel.

Disadvantages
There are several possible disadvantages that may arise with 4x4. For starters, let’s talk about power. The highest end FX dual-core processors take up about 100W a piece, non-overclocked or over-volted. Now, multiply that by two. In days where we talk about 300W graphics cards and cringe at having to by 600W+ power supplies, we often forget how much power CPUs really need. Powering a 4x4 system will be a stiff wakeup call. With high power, comes high heat. It’s not going to be easy keeping two processors cool while keeping the case temperature at a reasonable level. You will most likely need a case with very good ventilation to keep temperatures down. This also lets us segue into what seems to be a fundamental flaw in the design. The 4x4 platform is being marketed as the ultimate enthusiast product. However, dissipating the heat from two overclocked processors doesn’t seem like something that very many people will be able to do. Also, while the complex design between CPU’s and chipsets is neat, the more complicated you make things the less flexible they are. Maintaining a stable, synchronous frequency past stock settings on one HT link is one thing, but two or three? That is really pushing it. We can easily see the overclocking ability of the chips to be far less than that of their AM2/1 processor brethren. Finally, we must address the housing of this platform. We can’t imagine a setup with two processors and all the features listed that will fit into a standard ATX form factor. You will almost assuredly need a case that accepts E-ATX boards if you want a fully featured 4x4 motherboard. However, we have seen an ASUS 4x4 board in person that fits quite nicely on a standard ATX form factor, but it was missing several of the features that are, be default, provided by the nForce 680a chipset. So those of you that prefer the small form factor or even the mid-tower cases can expect to pony up for massive monsters like the Thermaltake Armor/Kandalf or the Coolermaster CM Stacker, which specify E-ATX compatibility. I’m personally a fan of massive cases, so I don’t see this as a major concern, but you SFF enthusiasts will never see a 4x4 Shuttle.

Not an enterprise server rebadged
On the surface, 4x4 looks like it’s nothing more than a dual Opteron system with some flashy marketing and pretty motherboards. However, it is better to think of 4x4 as a quad-core gaming platform than a dual processor workstation. The main thing that really differentiates between the gaming/enthusiast world and the enterprise world is fault tolerance. In the enterprise world, performance is a sacrificed in favor of fault tolerance every single time a choice between the two can be made. The perfect example of this is ECC RAM. It runs slowly and is more expensive, but it can correct RAM errors on the fly instead of crashing the computer. In the real world, a computer crash can be much more expensive than some dinky sticks of RAM. The overall sacrifice of speed is shown all over the enterprise platform, even in the chipsets. The 4x4 platform takes the enthusiast approach and pulls out all the stops in order to get the best performance possible in a given configuration. Since it lacks the concentration on fault tolerance, it really can’t be accurately described as an enterprise solution. Other distinctions are shown in the peripherals integrated into a motherboard. Enterprise boards commonly have PCI-X and SAS slots these days, but they lack any sort of audio output. The 680a chipset isn’t designed for PCI-X or SAS and comes with the HD audio chips that are standard on enthusiast boards. Basically, if we shrunk down both processors to fit onto one package, then connected them with a HyperTransport link, we would have a simple quad core gaming platform. Don’t be fooled by the number of processors, this is no enterprise server.

The announcement of 4x4 has received a rather cool reception in the community and time will tell if it’s a big flop or a big hit. Hopefully you can use this article to form a more accurate opinion of the technology, since it is still a mystery to many. Just a quick summary of the points:

Advantages:
+Fast chip-to-chip interconnect
+Amazingly feature-rich chipset to launch on
+Future quad core compatibility

Disadvantages:
-Dual processors probably means an E-ATX board
-Cooling dual processors is tricky
-Overclocking such a complicated system can’t be easy