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AMD's Sempron 2800+ and 3100+ processors

The Celeron gets a new rival

VALUE PROCESSORS ARE all about artful foot-dragging. They are somewhat slower versions of the familiar Athlons and Pentiums, reworked and re-branded to sell at lower prices in cheaper PCs. At the high end of the market, we get to witness an epic struggle between AMD and Intel's best processors for all-out supremacy, but in the value realm, we witness something rather different. The point isn't to beat the other guy's product at any cost; it's a high-wire act in which the performers must balance beating the other guy's performance against the possibility of cannibalizing sales of one's own more expensive products.

For a while, AMD did a nice job balancing those concerns with the Duron processor, a direct competitor to Intel's Celeron. However, with the introduction of the Athlon 64 processor, the Duron started to fade away. The Athlon XP became AMD's low-end product, which only made sense given its mix of price and performance. However, the rise of this two-tiered Athlon lineup created confusion for a lot of folks, who were asking questions like, "Why should I pay more for this Athlon 64 3200+ when the Athlon XP 3200+ would seem to be just as good?"

That's a good question, and there are some good answers, too. But try explaining those answers to Joe Sixpack before his eyes glaze over—as phrases like "extra registers," "64-bit addressing" and "integrated memory controller" come gushing forth from your geeky face—and you'll start to understand the pickle AMD's marketing folks found themselves facing. So AMD decided it was time to resurrect a distinct value product line, and the AMD Sempron was born.

Yep, that's the name: Sempron. AMD has elected to stick with its "fake subatomic particle" naming scheme rather than veer into Intel's "fake member of the periodic table of elements" naming scheme. Sempron is largely a branding exercise, so the name is important. The Sempron name is intended to evoke phrases like "semper fidelis" and other such tokens of solidity and steadfastness. Roughly translated from a mix of Latin and leet-speak, though, Sempron means "always pornographic," and I fear the little CPU will never fully escape that connotation of its recently fabricated moniker. As for why AMD decided not to reuse the Duron name, all I can say is that the intricacies of product branding strategies escape me.

The new processors
The Sempron is a new product line, but regular TR readers will be familiar with the processors themselves already. The majority of Semprons, right now, are renamed Athlon XP processors with new model numbers and a slightly different mix of clock and bus speeds. Like the Athlon XP, these products drop into Socket A motherboards. They are, in fact, based on the Thoroughbred core, with 256K of L2 cache—or more accurately, they're most likely based on the revamped Thoroughbred B core, rebuilt for higher clock speeds. Other than the name, they're virtually indistinguishable from an Athlon XP.

The AMD Sempron 2800+

All Socket A Semprons are intended to run on a 333MHz front-side bus, so they are a little more potent than some older Athlon XPs, but less potent than the fastest Athlon XPs, which pack 512K of L2 cache and ride on a 400MHz bus.

Beyond the bus speed tweak and name change, the Semprons get a new model numbering scheme that's (shh, don't tell) obviously indexed against the clock speeds of competing Celeron models. The Sempron 2800+ pictured above runs at 2GHz, and AMD intends it as a competitor for the Celeron D model 335, whose clock speed is 2.8GHz. Hence the 2800+ model number. I'll leave it to the branding gurus in AMD marketing to explain why they didn't just go ahead and riff on Intel's new three-digit numbering scheme. "Sempron 335 GT" or some such would have made sense to me, but like I said, this stuff escapes me.

The Socket A Semprons will stretch down to the 2400+ model running at 1.67GHz, but don't think the future of the Sempron is in Socket A. Already, AMD is defining the Sempron's future path by introducing a K8-derived Sempron, the 3100+, that slips into Socket 754 motherboards, just like most Athlon 64 processors. The K8-derived Sempron has a number of natural advantages over the Socket A version. It shares the A64's unique system architecture, in which the memory controller is integrated onto the CPU and high-speed HyperTransport links connect the processor to the rest of the system. The K8 Sempron also has support for SSE2 instructions, and like the Athlon 64, it's fabricated using AMD's 130nm silicon-on-insulator (SOI) process.

The Sempron 3100+ rides in Socket 754 mobos

However, AMD's marketing folks have lobotomized the Athlon 64 "Newcastle" core in order to keep Sempron from beating up on its big brother. Like the Socket A Sempron, the K8 version has only 256K of L2 cache, and it can't do 64-bit addressing. By virtue of its Socket 754 pinout, the Sempron can only converse with a single channel of DDR400 memory at once. Also, the Socket 754 Sempron's HyperTransport link officially peaks out at 1.6GHz, while newer Athlon 64s support 2GHz HyperTransport speeds.

Even though the K8 core's main pipeline is slightly longer than the Athlon XP's, the K8 Sempron ought to be quite a bit faster, clock for clock, than the Socket A Semprons. As a result, the Sempron 3100+ ticks along at a leisurely 1.8GHz.