AMD Athlon II X4 620 review - AMD Athlon II X4 architecture

AMD Athlon II X4 architecture

What you'll notice with the new Athlon II X4 processors is that the architecture (based on the Propus core) shows a lot of similarities to Phenom II, and of course that was the building block for this new, somewhat cheaper design of processor. The biggest change is that 6MB Level 3 cache being cut away.

But let's walk through the Athlon II X4 architecture for a moment. Recently AMD made a move to their 45nm node to manufacture the newer model processors. Much like Phenom II, the Propus core inside the Athlon II X4 is now made on a 45nm node. If you look at this from a distance it pretty much means that they were able to make this processor smaller compared to the last generation products. The die-size of this processor is now measuring only 169 mm².

A smaller fab size means advantages, often to be found in lower voltages and higher clock frequencies. The fastest Athlon II X4, the 630, will run at 2.8 GHz at a full 2.0 GHz HT 3.0 speed. The processor we are testing today is the Athlon II X4 620 which is running at a 2600 MHz clock frequency. Voltage ranges are 0.925 to 1.425V. This processor generation has a slightly increased maximum peak wattage of 95 Watts (TDP). Being an AM3 package, the processor is both motherboard Socket AM2+ and AM3 compatible.

The big difference
This Athlon II X4 part is based on AMD's 45nm Silicon on Insulator process technology and has a total of 2MB L2 cache; 512KB per core. However -- a big change in Phenom II architecture was a large increase in L3 cache. Phenom II can address 6MB L3 cache shared among the cores as a buffer, so it can exchange data in-between the four logical cores. And it's exactly that part that has been stripped away from the Athlon II X4.

• L1 Cache (Instruction + Data): 128KB x4 (64KB + 64KB for each core)
• L2 Cache: 512KB x4 (quad-core)
• L3 Cache: 6MB Shared L3

L3 is where a lot of magic happens and is the reason for Phenom II's success. How much of an effect will this have on overall performance? Well, quite a bit really but that's what we'll find out in our benchmark session.

AMD Phenom II X4 die

AMD Athlon II X4 die

Unlocking that L3 cache?
A few overclockers have found recent success turning an Athon II X4 620 or 630 CPU into a fully-fledged Phenom II X4 just by activating ACC in the BIOS. Instead of a core being unlocked, the ACC is capable of activating the 6MB of L3 cache turned off on the chip. Here's the thing, if you have the older Deneb based processor... you might be in luck. Propus, as explained however, has this cache physically missing and as such it's just not possible to unlock it.