Architectural Changes from Conroe to Penryn



The new Core 2 Series of CPU based on the Penryn architecture will include a few new surprises over the original Conroe design which we plan to cover here. The first big one is Intel’s change of transistors from the Silicon/Silicon Dioxide type to what’s now known as High-K metal gate. With the reduction in size Intel has gone to extreme lengths to boost the voltage leak factor that affects the 65nm series CPU as well as boost the switching speed of the transistors, the High-K metal Gate series is supposed to do that.

Next on the list is Penryn’s boost to the L2 cache side of things. Currently there are two series of CPU that will come out using the Penryn architecture, Yorkfield is the quad core series and Wolfdale is the dual core series under the Core 2 brand. On the current Conroe Core 2 Duo, cache sizes have been 2MB shares across the two dies, and 4MB for quad core as each separate die has its own L2 cache. Wolfdale dual core goes up by 4MB to a total of 6MB for Core 2 Duo and Yorkfield goes to 12MB since it has two Wolfdale cores on its single CPU package. While this is nice to see, there is still one problem with the Yorkfield CPU and that is communication between the two dies.


On Kentsfield cores, in order for Die A to communicate with Die B, a request has to be sent along the FSB, back to the northbridge and then along the memory bus; so while the two cores on Die A can communicate across the L2 cache, and the two cores on Die B can communicate the same way, in order for the two cores on Die A to know what the two cores on Die B are doing is a somewhat long and slow process.

Yorkfield hasn’t changed this either as the same method is used, and while the FSB is at 1333MHz to try and reduce this delay, it’s still not fast enough and a true quad core with all four cores on a single die sharing a single L2 cache must come from Intel very soon to offset this stumble. Compared to Phenom, Intel’s quad core is simply multi core technology.

Next on our upgrade list is the inclusion of a new set of multimedia instructions, these known as SSE4. The new SSE set contains 54 new instructions designed to speed up the video editing and multimedia rendering on the Penryn based CPU. SSE4 brings a new level of simplicity for the video rendering system by doing away with complex strings of commands needed with SSE3 series chips. Penryn only supports SSE4.1 which is revision 1 of the SSE4 instructions, and only 47 out of the 54 are included. We will have to wait for the next revision to come in for us to get the final seven instructions which will hopefully speed up game performance once they support SSE4.