A number of MacCentral readers have noticed a starkly different set of processor and cache configurations between the international 500MHz iMac and the North American version. In addition, international models appear to be using the ATI Rage 128 Pro chip, where the North American version is using the newer ATI Rage 128 Ultra with 16MB of memory.
A check of configurations listed on ten different European Apple Store Web sites shows the 500MHz iMac using a 512K L2 cache at 200MHz — presumably the Motorola 750 processor (see first screen shot below). The North American version is listed as using a 256K L2 cache at 500MHz — using the IBM PowerPC 750cx processor (see second screen shot below).
The assumption of a different processor on the international version is based on that fact that the U.S./Canadian product is using a cache equal in speed to the processor, which means the cache is built in to the chip. That would mean the use of the IBM PowerPC 750cx in the North American model, and the Motorola 750 processor in the international model.
The MPC 750 has a much bigger cache than the IBM processor, 512K, but instead uses a backside cache at speeds of half the processor or less compared to the IBM product.
In addition to an apparent processor difference, the 500MHz international iMac model is using the ATI Rage 128 Pro graphics chip with 8MB of RAM instead of the newer Rage 128 Ultra chipset with 16MB of RAM that the US model features.
Not only is the international 500MHz model US$29 more in price than the North American model, but potential customers are commenting they are getting what appears to be less of an iMac for almost the same price as their North American counterparts. The international version uses what many believe is a slower, less sophisticated graphics card with half the graphics memory and a Motorola processor, which is marginally slower in part because of the smaller cache size, according to Motorola specification data.
Just what exactly are the differences between the Rage 128 Ultra and the Rage 128 Pro is not fully known as ATI has yet to release detailed information on the 128 Ultra chipset.
The reasons for the two differences on the 500MHz iMac are unknown. Some MacCentral readers speculate the difference could be for international importation reasons related to certain components, or shortages of either IBM 750cx chips and/or Rage 128 Ultra chips. Others are guessing the specifications could simply be wrong on international Apple Stores sites.
An Apple spokesperson was not immediately available for comment on the discrepancies.