AMD Phenom II X4 940 & 920 Processors

The Phenom II - A Little More In-Depth:

By now you have to be wondering why the Northbridge Frequency (HT/MC) is running only at 1.8GHz while the older high-end Phenoms are running at 2GHz. The short answer is that AMD had to clock them down a little to make the launch date for these two chips. They have assured us with the upcoming AM3 processors that the frequency will be back up to 2GHz.

Remember earlier when I said the Phenom II is more than just a die shrink? Here's a short list of some silicon enhancements for the Phenom II:

• 45nm immersion lithography manufacturing technology enables higher frequencies, tighter tolerances and lower current leakage
• 6MB L3 cache (up from 65nm Phenom's 2MB)
• 2-cycles faster than 65nm Phenom L3
• Increased DRAM bandwidth
• Cache flush on halt: Core's L1 and L2 flush into shared L3 after a core enters a halt state allowing the core to drop to a lower speed and save power
• Path-based indirect branch prediction
• 2x increase in core probe bandwidth
• Larger load/store buffering / larger floating point buffering / reduced MAB (missed buffer) lifetime
• Improved LOCK pipelineing: (LOCK is an instruction prefix) this improves performance when multiple LOCKS are in process simultaneously
• FP MOV compute optimization: Floating point register-to-register move instruction improvements

Cool'n'Quiet 3.0:

AMD has not only improved performance, but pushed power saving features to new levels. Cool'n'Quiet 3.0 promises to deliver significant power savings over previous CnQ versions with minimal performance impact.

In the past Phenom's we've all seen some quirkiness with CnQ in terms of affecting performance and usually the recommended fix would be to just disable CnQ in the BIOS. Without going into specifics it had to do with how CnQ could independently down-clock each core and sometimes a thread would get bounced to a core that was throttled down. With the Phenom II AMD fixed that by having all cores running at the same speed.

I did do some brief testing with the Phenom II with CnQ 3.0 enabled vs disabled and I honestly have nothing bad to say. Hopefully soon I'll get a chance to take a much more thorough look and get some solid numbers up in another article. For those interested, with CnQ enabled the CPU speed will drop down to 800 MHz (4x multi) and the voltage drops too.

Socket AM3 & DDR3 Memory:

While the two Phenom II processors launched today are socket AM2+ only, AMD has said that the AM3 Phenom IIs will follow very soon. The main difference for socket AM3 is the switch from DDR2 to DDR3 memory! AMD has made a very smart move by keeping the upcoming AM3 processors backwards compatible with AM2+ motherboards. In Layman's terms, you will be able to put the future AM3 processors in AM3 or AM2+ motherboards. However, you can NOT put an older AM2+ processor in a future AM3 board.

Current AM2+ motherboards are very reasonably priced and available everywhere. I'm sure we will see a few AM3 motherboard models available when the AM3 CPUs launch, and then a slow trickle of new models thereafter. DDR3 memory prices have come down considerably, but if you are on a real budget there is plenty of DDR2 memory out there that is dirt cheap after MIRs.

There haven't been any solid numbers available on the performance gained using DDR3, but the graph below shows us roughly what can be expected. I'm sure there is plenty of room for improvement when you start to overclock it.