Re: Intel Corp. officially rolls out its first two quad-core CPUs Monday
It looks like a nice part for low to mid range single and dual socket servers (which covers a lot of territory).
Intel's only problem is that it isn't actually a quad core chip, it's a module with two dual core chips on it that presents 2 loads to the front side bus. But that's only a problem in high end systems that use more than 2 sockets (quad and octal socket systems). They get around most aspects of the problem in Bensley based systems by putting a crossbar in the North Bridge which lets them run two 3 load interfaces at 1333mhz. That only uses 1,432 pins (which is easily manageable, these days) but it means that to go beyond 2 sockets is a problem. To support a 4 socket server, you need most of those connections, times two, going to a single socket, and that makes motherboard routing difficult (you address the issue by adding a lot of additional layers to the board). Pin counts are almost unlimited due to new ball bonding techniques. The days of high pin counts being an issue are over. But concentration of motherboard traces and motherboard routing is still an issue.
Opterons have a crossbar switch in each CPU that runs 3 * 2ghz point to point interfaces on each CPU plus 2 memory interfaces. Opterons distribute the interconnection work while Xeons concentrate it all at the chipset north bridge. Each approach has benefits and drawbacks. A single CPU Opteron system has a lot of complex and expensive (in terms of transistor budget) hardware that isn't used. But it easily scales to large systems. Xeon systems move a lot of that functionality to the North Bridge (crossbar and memory controllers) but that tends to overload the north bridge if you try to go beyond 2 sockets.
Note that Xeon systems can also be built by stringing the CPUs along a bus, but as you add loads to the single bus, you have to run the bus slower at the same time that data transmission requirements are increasing - it's a less effective design and Intel has been moving away from it. The old-style bus based dual and quad (and more) Xeon systems had horrible scaling under many work loads. The newer multiple FSB North Bridge design Xeon systems are much better, but have issues going beyond two sockets, whereas Opteron systems with their built in crossbars and distributed memory controllers scale easily to 8 socket systems.
Two approaches to server design, each with benefits and drawbacks. Current 8 socket Opteron systems support quad core chips that will become available next year. But it means the Opterons themselves are more complex to design and produce (and won't be available for a quarter or two) whereas the Xeon modules are available now, even if they're limited to dual socket designs (quad socket if Intel can ship its quad FSB north bridge and motherboard, which it has demoed, but looks a little scary).
theinquirer.net
Note that an Opteron based 4 or 8 socket system needs no north bridge at all. The converse of that statement is that Xeon needs no crossbar or memory controller. Two very different design choices. |
