AMD Bulldozer: The fightback begins in 2011

15th Jan 2010 | 11:00

AMD Bulldozer: The fightback begins in 2011

Why AMD's future cores aren't like Intel's cores

Bulldozer bowls up

Have you been keeping up with the latest brand-pimping ad campaign from Intel? If so, you'll know the basic shizzle involves Intel's super-geeky employees looking at life a bit differently.

"Our rock stars," says Intel, "aren't like your rock stars." Instead, Intel's rock stars are engineers of esoteric tech like the USB interface.

Replace 'rock stars' with parties, perks, jokes and co-workers and you have a series of semi-funny viral webverts. All moderately amusing, no doubt. But could it be AMD, Intel's main rival in the computer chip business, that has the last laugh?

Bulldozer bowls up

Maybe, just maybe. AMD is belatedly tooling up to release a revolutionary new processor architecture that will fundamentally challenge the notion of what exactly a CPU core is. If everything goes to plan, it wouldn't be altogether surprising to soon find AMD tweaking Intel's nether regions with a familiar slogan along the lines of ,"Our cores aren't like your cores."

Of course, it's hardly a given that things will go to plan for AMD. After all, this new architecture, known as Bulldozer, was supposed to be on sale last year. At best, we'll see it early in 2011.

But let's assume Bulldozer does hit its revised launch date. Why is it revolutionary and how much damage might it do to Intel?

Core blimey

For starters, Bulldozer is AMD's first properly new processor architecture since the Athlon 64 of 2003. Every AMD chip since then has been a variation on that theme. A tweak here, an added core or floating point unit there, perhaps. But basically the same design.

Not so for Bulldozer. It's a genuinely novel architecture. Novel enough, in fact, to make describing it something of a semantic assault course.

Instead of traditional execution cores, Bulldozer chips will be made up of one or more "modules". Each module packs a pair of integer units and a single shared floating-point resource. The latter is actually a pair of 128-bit FMACs, but lets not get ahead of ourselves.

Core of the matter

Things get confusing because AMD is referring to the integer units as "cores". Admittedly, each unit does get its own scheduling circuitry and L1 cache memory. But they share both instruction fetching and decoding hardware across the module. Not quite proper cores then.

In fact, it could make more sense to think of the dual integer units as AMD's answer to Intel's HyperThreading technology. But unlike HyperThreading, which is all about making better use of a single execution resource by sharing it across two threads, AMD has given Bulldozer some dedicated hardware for each thread and hence very likely much more multi-threaded performance.

However you slice it, Bulldozer is going to make a mess of easy comparisons based on cores. On the one hand, each module looks like a dual-core unit with certain compromises enabling AMD to fluff up its core counts. On the other, it's a single very heavy duty core with superior multi-threading throughput to anything we've yet seen in the PC.

What about the performance?

What about the performance?

Ultimately, of course, the war of words will give way to a more relevant battle for the real world performance crown. Much will come down to the number of modules AMD manages to cram in. Early indications suggest that the first Bulldozer chips will have four modules and hence will probably be marketed as eight-core chips.

But by then, Intel could well be flogging CPUs with eight full-on cores. In that context, Bulldozer is unlikely to be the fastest CPU you can buy when it arrives. What it very probably will do, however, is lift AMD out of its current budget niche and allow it to take on Intel in the meaty, lucrative market for midrange performance CPUs.

Power not price

No longer will AMD chips compete almost purely on price, in other words. That said, there are doubts that will need to be addressed. It's not clear, for instance, how well a Bulldozer module will perform in the floating point workloads that are increasingly common in our modern multimedia world.

The problem here is twofold. Not only does Bulldozer have just a single floating point unit for each pair of integer units. It's also limited to executing floating point instructions in 128-bit chunks. By early 2011, Intel should have launched its Sandy Bridge architecture complete with 256-bit floating-point power.

The upshot of which is that in certain scenarios, Intel's chips could have four times the floating point performance per integer unit. That's a bit scary. Maybe it will Intel rolling out the "Our cores aren't like your cores" gag after all.

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