Wednesday, August 18, 2004

Dual-core G4 in October

Freescale will introduce its dual-core G4-based e600 chip (PDF) on October 5th at the 2004 Fall Processor Forum.

The dual-core support in this 2+ GHz G4-class chip is interesting, but just as interesting is its integrated memory controller, which is a long time coming. The current G4 (MPC7447A) does not have the ability to communicate with memory at DDR speeds. Thus, any machine using DDR with a current G4 has effectively half the memory bandwidth when communicating with the CPU. The new dual-core e600 (and possibly single-core variants) will go a long way to alleviate the memory bandwidth constraints plaguing current G4 designs.

One may ask if this chip can compete with the G5. In many ways, yes, most definitely. Freescale is not known for being at the forefront of process technology or raw performance, but it is very well respected when it comes to low power embedded designs. Freescale's e600 will undoubtedly offer a very good speed to wattage ratio, and it will most likely compete favourably with IBM's 970FX in comparative MHz-for-MHz performance, at least when it comes to integer and Altivec code.

However, it's hard to see where a dual-core e600 will fit into Apple's lineup, at least in the near term. The new iMacs and Power Macs are using IBM's G5 970FX, and it's likely that the PowerBook will get this chip as well, in 2005. That leaves the eMac and iBook. Of these two machines, the most likely machine to use a next-generation G4-class chip would be the iBook, but dual-core is not necessary. Thus, it will be interesting to see what Freescale has to offer in single-core G4-class designs in the near future. At this point it is not clear if Freescale will be able to bring a single-core e600 variant to market quickly, or if it will continue to scale its current G4 design (which does not have true DDR support) to higher speeds. Possibly both, with the single-core e600 coming later. In the meantime, the iBook still has room to scale, since the G4 7447A is already available up to 1.5 GHz, and the current top-end iBook is at 1.2 GHz.

Update August 20, 2004:

The Register last year published an article that suggests Freescale could produce this chip with a power spec of 25 Watts at 1.5 GHz, utilizing a 90 nm process. That seems rather optimistic, but if true, then it would mean that a dual 1.5 GHz (or possibly even a dual 1.8 GHz) G4 PowerBook is feasible. However, this assumes that the 25 Watt spec is true, that Apple wants another 32-bit PowerBook, and that Apple is willing to bet on Freescale's 90 nm shrink (despite Freescale's history of delayed process shrinks compared to the competition), when IBM has already solved its 90 nm problems and could ship a laptop oriented single-core G5 970FX chip (perhaps up to 1.9 GHz) in fairly short order comparatively.

We shall see in 2005.

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