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Dual-Core Alphabet Soup: Athlon, Phenom—Both X2s

AMD Athlon II X2 / Phenom II X2 And Low-Power CPU Bonanza

Perhaps I was a little whiney when AMD launched its Phenom II X4 810 and Phenom II X3 720 Black Edition, claiming that the naming was getting a little ridiculous, if not difficult to keep straight. But now that we have yet another product family to add to the stack, it only gets more convoluted. Take the following slide from AMD’s press briefing:

Along this performance continuum we have Athlon X2s (with and without L3 cache), Phenom X3s, Athlon II X2s, Phenom II X2s, Phenom II X3s, and Phenom II X4s. Missing are the original Phenom X4s as well as the Athlon II X3 and Athlon II X4 expected in July.

I’m not about to defend Intel’s lineup. Core 2 Duo, Core 2 Quad, and Core i7 are easy enough to keep straight, but it’s quite a bit harder to remember what the Q9000-, Q8000-, E8000-, E7000-, E6000-, E5000-, and Celeron E1000-, and 400-series models really include. And as you travel down the lineup, you start giving up virtualization support, SSE 4.1, vPro, etc. The whole concept of whittling off features in the name of product differentiation becomes problematic, especially in the face of upcoming Windows 7’s “XP Mode,” which uses virtualization to facilitate application compatibility with older software. When you consider that this is a capability aimed at businesses, and given that many businesses celebrate the stable image of Intel’s platforms, we already see it becoming easy fodder for AMD’s marketing cannon. Whoever it was at Intel who thought up the idea of axing virtualization as a good differentiator must have missed a meeting with Microsoft.

AMD's Athlon II X2: RegorAMD's Athlon II X2: Regor

The point is that AMD’s Athlon II X2 gives you yet another architecture to keep straight. This one sports the 64 KB of L1 data/instruction cache per core common to all of the Phenoms and Athlon X2s and 1 MB of L2 cache per core—there is no L3. Internally referred to as the Regor core, the Athlon II X2 is manufactured at 45 nm, resulting in a 234 million transistor die measuring a tidy 117.5 square millimeters. It’s compelling, then, that the processor is rated at a 65 W TDP. Also notable is that this is AMD’s first processor with the C1E enhanced halt state enabled in hardware. Past processors have required BIOS updates in order to add support; this is no longer the case. Sigh. At least performance and socket/memory compatibility are the only ways in which all of these processor families differ.

AMD is only announcing one model at launch: the Athlon II X2 250 running at 3 GHz. With a northbridge clocked at 2 GHz and a memory controller capable of supporting DDR2-1066/DDR3-1333, this native dual-core processor looks like it could be a strong mainstream contender. Given an $87 price point, we expect this one to go up against Intel’s Pentium E6300.

AMD Athlon II X2 250
AMD Phenom II X2 550 BE
Intel Pentium E6300
CoreRegor (dual-core)
Callisto (dual-core)
Wolfdale-2M (dual-core)
Manufacturing Process
45 nm
45 nm
45 nm
3.0 GHz
3.1 GHz
2.8 GHz
L1 Cache (I / D)
64 KB / 64 KB64 KB / 64 KB32 KB / 32 KB
L2 Cache
1 MB/Core
512 KB/Core2 MB Shared
L3 Cache
6 MB Shared
65 W
80 W
65 W
4,000 MT/s
4,000 MT/s
1,066 MT/s

The Athlon II X2 looks like a darling—right up until you see the other dual-core chip AMD is unveiling: its Phenom II X2. Based on what is being referred to as the Callisto design, you can also think of this CPU as Deneb minus two execution cores; everything else remains intact.

Phenom II X2: Callisto (Deneb with two cores turned off)Phenom II X2: Callisto (Deneb with two cores turned off)

Again, we have 64 KB of L1 data/instruction cache per core, and like AMD’s other Phenom IIs, this one sports 512 KB of L2 cache per core and a 6 MB shared L3. There's a 2 GHz memory controller with DDR2-1066/DDR3-1333 support, Socket AM3 interface—am I sounding like a broken record yet? Take a Deneb. Lop off two cores. Voila, Callisto. Only the cores haven’t been lopped off. They’re still there. More on this in a couple of pages.

The only model in this family that AMD is discussing today is its Phenom II X2 550 Black Edition, which cruises along at 3.1 GHz, costs $102 ($15 bucks more than the Athlon II X2 250), and sports the unlocked multiplier synonymous with AMD's Black Edition modifier. Of course, it’s manufactured on the Globalfoundries 45 nm process and, being based on Deneb, consists of a whopping 758 million transistors in a 258 square millimeter die. Because two of the chip’s cores are turned off, its TDP drops to 80 W.

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