Turbo Core/Specifications

Like Intel, AMD obviously realizes that there are cases when all the processing cores inside their latest multi-core CPUs aren’t being used. Even today, many software apps are only single or dual-threaded, leaving two core idling in a quad-core CPU, and four cores idling in the case of a six-core Thuban CPU.

To address this issue, AMD offered application profiles in their latest builds of Overdrive that would automatically OC the active processing cores when certain programs were run.

This software-based solution required AMD to constantly update their profile database in Overdrive to properly work, and of course it requires the end user to actually run AMD’s Overdrive software at all times.

In other words, it’s an inelegant solution to the problem. A hardware-based solution that requires no effort from the end user, yet still delivers comparable results is more desirable. In addition, Turbo Core can help make up for some of the clock speed deficit that Thuban suffers from in comparison to today’s Deneb-based Phenom II X4 processors.

With Turbo Core, Thuban is capable of watching the utilization of the CPU’s six cores. If three or more cores aren’t currently being used by the app, the CPU can reduce the power state on those cores, and Turbo up the three cores that are being used. The unused cores can be idled down to as low as 800MHz, while the active cores can be OC’ed up to 500MHz on certain CPUs.

Notice that we said “active cores can be OC’ed up to 500MHz”, and “unused cores can be idled down to as low as 800MHz”. It’s important to note that these aren’t 100% guaranteed conditions. To keep the Thuban CPU within its 125W TDP, the CPU can’t always OC the active cores the full 500MHz. In some cases the active cores may just be clocked up 100MHz, or say 300MHz. We also noticed that the inactive cores don’t always go down to the full 800MHz clock speed. Sometimes they may be running at 1000MHz. This is a little different than Intel’s Turbo feature, which definitely does bump up the clocks the full 100% if certain conditions are met.

Also unlike Intel’s Turbo Mode, AMD Turbo Core kicks in only when three or more cores are being used. This means in cases where four cores are being taxed, AMD Turbo Core doesn’t do anything. It also doesn’t completely shut down the inactive cores like Intel Turbo Mode does. As a result, it isn’t as power efficient.

In other words, it’s definitely still much less advanced than what Intel’s offering with their latest CPUs, but it’s definitely an improvement over relying on AMD Overdrive software. It’s an incremental step that will hopefully be improved when AMD launches their next-generation Bulldozer CPUs next year.

All AMD CPUs with Turbo Core technology will be denoted with a “T” after the model number. So today we’re getting the 1090T and the 1055T CPUs, and in the future we’ll supposedly see 1075T and 1045T processors if you believe the rumors.

With that discussion out of the way, let’s go over the rest of the Thuban CPU’s specs:

AMD’s Phenom II CPU Lineup
	Phenom II X6 1090T BE	Phenom II X6 1055T	Phenom II X4 965 BE	Phenom II X4 955 BE	Phenom II X4 945	Phenom II X4 925
# of Cores	6	6	4	4	4	4
Clock Speed	3.2GHz	2.8GHz	3.4GHz	3.2GHz	3.0GHz	2.8GHz
Max Turbo Speed	3.6GHz	3.3GHz	N/A	N/A	N/A	N/A
L2 Cache Size	2MB	2MB	2MB	2MB	2MB	2MB
L3 Cache Size	6MB	6MB	6MB	6MB	6MB	6MB
TDP	125W	125W	125W/140W	125W	95W	95W
Price	$295	$199	$185	$165	$155	$145
Die Size	346mm2	346mm2	258mm2	258mm2	258mm2	258mm2
NOTE: Excludes Phenom II EE CPUs

Notes

If you recall our review of Intel’s Core i7-980X six-core CPU, you’ll remember that it ships with a larger 12MB L3 cache. Intel’s engineers increased the size of the L3 to maintain what they believe is the optimal ratio between L3 cache and cores which is 2MB of L3 cache per core (although keep in mind that the L3 cache is shared amongst all six cores, so one core can use as much cache as it needs, including the full 12MB L3 for single-threaded apps). Intel was able to increase the size of the CPU’s L3 cache without upping the chip’s die size thanks to its smaller 32-nm manufacturing process. Thanks to 32-nm, Intel could add cache without making the chip bigger, and thus it isn’t more expensive for Intel to produce (assuming of course Intel is getting equal yields which may or may not be the case).

With more L3 cache on board, the Core i7-980X was faster than the Core i7-975 even in cases where only four cores were being used. This is because the extra cache gave the CPU a performance boost in apps that weren’t threaded for six cores.

Since Thuban is built at 45-nm, AMD doesn’t have this luxury. The CPU’s die is already 88 square millimeters larger than Deneb. This comes from the two extra cores. If they would’ve bumped up the CPU’s L3 cache, the chip’s die size would be even larger and they wouldn’t be able to price it aggressively and still make money. As you can see in the chart above, it therefore ships with the same L2 and L3 cache configuration as quad-core Deneb Phenom II CPUs.

The future

While AMD won’t confirm it, the rumor mill says that AMD will eventually roll out quad-core Thuban CPUs later this year. These parts will merely have two of their processing cores disabled. Presumably the first CPU will be the Phenom II X4 960T. Rumors have also suggested we’ll see a 940T part at some time as well.