Even the Intel fanboys have to hand it to AMD once in a while. After Intel deftly dropped a Core i5 anvil on Phenom II’s head, AMD did a quick drop to floor and now fires back slo-mo style with its own chip: a $99 quad core.

Dubbed the Athlon II X4 620, this 2.6GHz quad core isn’t just leftover parts swept off the factory floor, either. The Athlon II X4 is based on the familiar K10 microarchitecture in the Phenom and Phenom II, but it’s actually a newer, smaller die. In fact, the new chip has less than half the transistors of a Phenom II X4 processor. Much of the shrinkage comes at the expense of cache. While the Phenom II packs 6MB of L3, the budget Athlon II X4 features none.

The TDP of the new Athlon II X4 chips (there are two, but only one is sub $100) is also considerably lower than the top-end Phenom II X4 965 Black Edition chip at 95 watts versus 140 watts. Other than the TDP and lack of L3 cache, the CPUs are essentially the same as their Phenom predecessors.

In fact, some Athlon II procs may actually be the same as Phenom II. Although the majority of Athlon IIs will be the smaller Propus cores, AMD will double-source the chips by taking some cores that might have been turned into Phenom II X4s and switching off the L3. Other than that, these chips will be virtually the same as a Propus—same TDP, same L2 cache, same clocks. While it might seem unusual, AMD says the practice is not unprecedented and happens quite often with budget CPUs. Because both the would-be Deneb and Propus cores are 45nm and essentially the same microarchitecture, it’s unlikely this will have any practical impact on the end user, the company says.

Still, the breakthrough here is not technology, but price. Up to now, the closest a budget user could get to a quad core was the stale Phenom X4 9650. At one time restricted to OEM sales, AMD has begun blowing these elderly parts out at about $110. The Phenom X4 9650 has 2MB of L3, but its slower Hyper Transport (3.6GHz vs. the Athlon II X4’s 4GHz) speed, lack of AM3 support (and thus DDR3), and its use of the older 65nm process technology make it a less attractive option.

In Intel land, the Athlon II X4’s main competition isn’t even close. Intel’s cheapest quad-core part today is the Core 2 Quad Q8200. Like the Athlon II X4, the Q8200’s low price is the result of a shrunken die size made possible by cutting cache. While the $220 Core 2 Quad Q9550 has 12MB of L2 cache, the $150 Core 2 Quad Q8200 has but 4MB of L2 cache.

Higher up the food chain, Intel made a significant technology and price breakthrough with the Core i5-750, but at $200 for the chip itself, it’s for folks with richer tastes. The extra $100 you can save with an Athlon II X4 is enough to buy an entry-level motherboard and the RAM to go with it.

To Quad or Not?

The budget buyer’s toughest question is whether to even opt for quad. Since price is the primary concern for the budget buyer, it’s worthwhile to consider all the various options in dual-core land. You could, for example, skip the Athlon II X4 620 in favor of the Athlon II X2 250. This would give you a 3GHz dual-core instead of the 2.6GHz quad-core and saves you about $13. Even cheaper, there’s AMD’s Athlon II X2 240, a 2.8GHz dual-core that’s listed at $60.

We didn’t run the performance numbers on these chips as we already know the answer: Which chip you buy should depend on what you do. Since the vast majority of games are not optimized for quad-core, a 3GHz dual-core will actually outperform a 2.6GHz quad core in gaming. The same can be said if you spend the bulk of your day in a browser or Microsoft Word: The two additional cores just don’t get you anything. On the other hand, if you encode media, edit photos, or you’re even an advanced Microsoft Excel user, a quad-core is well worth the dough. You don’t get double the performance everywhere, but for well-optimized apps, you could see substantial gains. How substantial? If an encoding job takes three hours on your 3GHz dual-core, it could take 1.6 hours on 2.6GHz quad core.

AMD’s new 45nm Propus core is at the heart of the new $99 Athlon II X4 quad-core.

Quad-cores will also pay dividends if you’re a heavy multitasker running more than one compute-intensive application at a time. Our final message to you is that a quad-core machine might actually get faster over time. That’s because apps are being continually upgraded and coding for four or more cores is a factor on most developers’ radar. That translates into faster performance on your quad core as the apps get updated.

 Quads Compared

 * Some Athlon II X4s will use Deneb cores with L3 cache disabled.

Next up, the performance tests and benchmarks.