Specs and overclocking

The following chart summarizes the differences between AMD’s 45-nm Deneb Phenom II CPUs versus the original 65-nm Phenom with Agena core:

Phenom II vs Phenom Feature Comparison
	Phenom II X4 940 Black Edition	Phenom X4 9950 Black Edition
Core	Deneb	Agena
Clock Speed	3.0GHz	2.6GHz
L1 Cache Size	64KB instruction+64KB data per core (512KB per CPU)	64KB instruction+64KB data per core (512KB total per CPU)
L2 Cache Size	512KB per core (2MB total per CPU)	512KB per core (2MB total per CPU)
L3 Cache Size	6MB (shared)	2MB (shared)
Memory Controller	Integrated 128-bit wide memory controller	Integrated 128-bit wide memory controller
Memory Controller Speed	1.8GHz with Dual Dynamic Power Management	2.0GHz with Dual Dynamic Power Management
Memory Types Supported	Support for unregistered DIMMs up to PC2 8500 (DDR2-1066MHz)	Support for unregistered DIMMs up to PC2 8500 (DDR2-1066MHz)
HyperTransport 3.0 Link	One 16-bit/16-bit link @ up to 3.6GHz full duplex (1.8GHz x2)	One 16-bit/16-bit link @ up to 4.0GHz full duplex (2.0GHz x2)
Total Processor Bandwidth	31.5 GB/s	33.1 GB/s
Packaging	Socket AM2+ 940-pin organic micro pin grid array (micro-PGA)	Socket AM2+ 940-pin organic micro pin grid array (micro-PGA)
Process Technology	45-nanometer DSL SOI (silicon-on-insulator) technology	65-nanometer DSL SOI (silicon-on-insulator) technology
Approximate Transistor count	~758 million	~ 450 million
Approximate Die Size	258 mm2	285 mm2
Nominal Voltage	0.875 - 1.5 Volts	1.05-1.30 Volts
Max Ambient Case Temp	62 degrees Celsius	61 degrees Celsius
Max TDP	125W	140W
Price	$275	$174

Notes

As you can see in the chart above, thanks to its smaller manufacturing process Deneb features a smaller die size than Agena (258 mm2 vs 285 mm2) despite its increase in transistor count (758M vs 450M). The bulk of the new transistors obviously come from the dramatically increased L3 cache size of 6MB (versus 2MB in Agena).

Thanks to its smaller die, Deneb is actually cheaper for AMD to produce than Agena, assuming equal yields (which may or may not be the case at this point considering the maturity of AMD’s 45-nm process).

The other spec that stands out is Phenom II 940’s slower memory controller. Running at just 1.8GHz, the new memory controller actually trails Phenom 9950 by 200MHz and is the same speed as the original Phenom 9600. Similarly, the HyperTransport interface runs in sync with the memory controller, operating at 1.8GHz. The net affect is overall CPU bandwidth is down from 33.1GB/sec in Phenom 9950 to just 31.5GB/sec in Phenom II 940.

We were told that this compromise was made in order to bring Phenom II to market today. Future AM3-based Phenom CPUs launching later this year will have this issue corrected, with memory controller/HyperTransport speeds in line with Agena’s 2.0GHz. We’ll also see a more diverse range of AM3-based Phenom II CPUs in comparison to AM2, with AMD eventually offering dual, triple, and quad-core AM3 Phenom II CPU offerings. In comparison it’s been rumored that AM2-based Phenom II may have an awfully short lifespan, with the 920 and 940 being the only AM2 Phenom II offerings to hit the market, with the CPU’s reaching end-of-life (EOL) status perhaps as soon as late Q2 of this year.

Rumors also point to the first AM3 processors arriving in a little over a month.

Normally this would be a cause of concern, but considering that AM3 CPUs are backward-compatible with today’s AM2+ platform, this shouldn’t be much of a problem. You can upgrade to AM2+ CPU today, and then transition to AM3 a year from now without having to buy another motherboard.

Looking at the nominal voltage in the chart above, you’ll also notice that Phenom II now tops out at as high as 1.5V compared to Agena’s 1.3V. Considering its smaller process, you’d normally expect the nominal voltage to be a little lower than AMD’s 65-nm parts.

In this case we were told that the fab likes to have lots of room to play with in terms of voltage when manufacturing CPUs. This obviously helps AMD obtain better yields than sticking with a narrower voltage range. Fortunately this shouldn’t affect max power consumption. One 3.0GHz part may come off the line running at 1.35V, while another may need 1.4V, but they’ll both still maintain a 125W max TDP. OC’ers though will probably want to hunt down the CPUs with the lowest voltage in the hopes that it will give them more headroom when overclocking (this may also be a case where AMD’s leaving themselves room for future CPUs running at higher clock speeds).

For what it’s worth, we noted an operating voltage of 1.336V for our particular Phenom II 940 sample.

Pricing

As we mentioned earlier, AMD’s providing two Phenom II X4 SKUs at launch, the Phenom II X4 940 Black Edition clocked at 3.0GHz, and the Phenom II X4 920 running at 2.8GHz. As a “Black Edition” part, the 940 ships with an unlocked clock multiplier, allowing enthusiasts to adjust the multiplier however they wish, while the 920 has a fixed multiplier setting of 14.0. The 940 is priced at $275 while the 920 is priced at $235. As always keep in mind that these are bulk prices AMD charges in quantities of 1,000, and not the CPU’s actual street price, which can actually be lower. The pricing of AMD’s existing 65-nm Phenom processors remains unchanged, with the 9950 BE and 9850 BE both officially selling for the same $174 and the 9750, 9650, and 9550 priced at $154.

CPUs are officially shipping as of now, and should be available for purchase in systems and at the retail level starting today.

Overclocking

Considering the enhancements AMD has integrated into Phenom II and its new 45-nm manufacturing process, we were eager to see how far we could push our particular Phenom II 940 BE chip. Starting with OCZ DDR2 RAM, MSI’s 790GX-based DKA790GX Platinum, and our trusty Zalman CNPS 9700-Cu cooler we anxiously dialed in speeds via AMD’s Overdrive utility.

First we wanted to see how far we could OC the processor at stock voltage. Here we maxed out at just 3.2GHz (200x16)! Any attempts to go any further and we’d get BSODs when running apps like Cinebench or gaming. Even cranking the HT speed up to 204MHz with the multiplier set at 16.0 eventually resulted in a BSOD when benchmarking.

So our particular sample wants more juice. All right, we’ll give it more voltage. We proceeded to crank up the HT speed and clock multiplier, running benchmarks all along to check stability. Eventually we ended up settling on a speed of 3.745GHz (16.5x227). We needed 1.55V of juice to get the CPU to run stable at that speed. We could boot and load Windows at higher speeds approaching 3.9GHz, but stability was sketchy at best at those speeds.

Keep in mind that we tested with 64-bit Windows Vista. With a 32-bit OS we probably could have pushed the processor a little further.