AMD Phenom II X4 940 & 920: A True Return to Competition
by Anand Lal Shimpi on January 8, 2009 12:00 AM EST- Posted in
- CPUs
Phenom II's Secret, In Pictures
I can be verbose, I know, I'm sorry - I'm working on it. But on this page, I'll use pictures to illustrate my point. Here's the 65nm Phenom die:
I highlighted one of the four cores in blue. The bottom part of the highlighted core its its 512KB L2 cache. The areas in pink are the 2MB L3 cache that is shared by all four cores. Now look at Phenom II:
Again we've got one of the four cores highlighted blue. The L1 cache size and the core itself look very similar to the original Phenom, but note how the new die is much more rectangular. The pink area represents the Phenom II's 6MB L3 cache.
Just comparing the two die you can see that while the individual cores look similar, the amount of L3 cache has gone up considerably. Remember that Intel found with Nehalem that an 8MB L3 cache was the bare minimum, leaving 2MB per core. The original Phenom had 2MB to share amongst all four cores, which is hardly enough; Phenom II fixes that. With a 6MB L3 cache and 512KB L2 per core, Phenom II looks a lot more like Core i7 from a compute-to-cache ratio:
Nehalem's layout makes a little more sense, with each core butting up against the shared L3 cache, but the point is that in both Phenom II and Core i7, the L3 cache is around 1/3 of the total die. The original Phenom alloted only 1/6th of the die for its L3.
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ViRGE - Thursday, January 8, 2009 - link
Those numbers are all correct, mate. I'm not sure why you'd be getting something different.Finally - Thursday, January 8, 2009 - link
Seriously guys, you should check out the new hard disk technology by Seagate. New density record, already available.kknd1967 - Thursday, January 8, 2009 - link
I thought Q9450 should be better with larger cache?Anand Lal Shimpi - Thursday, January 8, 2009 - link
In some of the tests the two will swap places simply because they run at the same clock speed and the added cache doesn't always help performance. In those cases if the Q9450 is behind it's most likely due to normal variation between test runs.Take care,
Anand
Goty - Thursday, January 8, 2009 - link
If I didn't have a 5000+ BE sitting in a K9A2 in my rig right now I probably wouldn't consider this CPU, but seeing as I do, it looks like I've found my next upgrade.kmmatney - Thursday, January 8, 2009 - link
I was on a plane flying back from Taiwan (I work in the Fab industry) and I happened to sit next to an Intel employee who had traveled to Asia for the Core i7 launch. I asked him about the small L2 cache, and he explained that these run about 300 test applications, and chose the cache amounts based on a compromise between performance (and latency) and die size. We talked a bit and he asked me how I knew so much about computer hardware, and I mentioned I'm an avid Anandtech reader. He recognized the name, and mentioned that he saw Anand argue with one of his coworkers for quite some time about the L2 cache size!Zaitsev - Thursday, January 8, 2009 - link
That's a great story! I would love to see anand duking it out with some intel employees! LOLslayerized - Thursday, January 8, 2009 - link
AMD has indeed made some notable improvements with Phenom II and their 45nm. Reviews keep mentioning about how there is an upgrade option with Phenom II being AM2 compatible; however, what next (this is probably their last product with AM2 compatibility)? Shouldn't the reviews consider the upgrade options for Core i7/X58 with Westmere in a couple of years too? For someone who is considering a fresh build, I think that is something that should be analyzed too imo. Great review otherwise as always; the playing field if not leveled is at least starting to look competitive in a few segments!!Griswold - Friday, January 9, 2009 - link
No. Facts and "might turn out that way in a few years" arent the same thing.san1s - Thursday, January 8, 2009 - link
still slower than core 2?