The first of a new generation of Mac systems based on the Common Hardware Reference Platform (CHRP) are about to arrive. Motorola has officially announced the first CHRP Macs and its new high-end line, called the StarMax Pro 6000, will be demonstrated for the first time this week at Macworld Expo in Boston.
In tests by Macworld Lab, the StarMax Pro 6000s pull far ahead of older machines, because they take advantage of CHRP's 66MHz bus speed (most Macs today use 40MHz to 50MHz buses). They also gain much of their speed from the PowerPC 750's (formerly code-named both Arthur and G3) new caching scheme, called "backside cache". Both backside cache and faster system buses help alleviate many of the performance bottlenecks of older systems, radically raising the overall performance bar for this new generation of Macs.
The PowerTower Pro G3 from Power Computing, another key system to be unveiled at Macworld Expo in Boston, will also be among the first to use the PowerPC 750 and showed outstanding results in our tests.
In most Macs today, the CPU and cache communicate through the system bus - which typically operates at 40MHz to 50MHz speeds. But the PowerPC 750's backside cache uses a separate, higher-speed cache connection reserved for CPU-to-cache (and cache-to-CPU) communications. The PowerPC 750's backside cache communicates with the CPU in 1:1, 2:3, 1:2, or 2:5 ratios. So, for example, a 300MHz PowerPC 750 can communicate with cache using a 300MHz, 200MHz, 150MHz, or 120MHz cache bus - several times faster than the previous limitation of the 40MHz to 50MHz bus speed.
Set to ship by the end of September, the StarMax Pro 6000/233, the 6000/266, and 6000/266 XL provide 512K of cache, which communicates with the CPU in a 2:1 ratio, for 117MHz and 133MHz cache buses, respectively.
The StarMax Pro 6000/300, expected to ship in October, will come with 1MB of backside cache communicating with the CPU in a 3:2 ratio, for a 200MHz cache bus.
In addition to improving raw performance, the CHRP specification also helps create a more open platform, since the Mac licensees will no longer be using Apple-designed motherboards - whose circuitry is often partially undocumented, requiring the clone makers to turn to Apple for help. Clone makers should be able to move at their own pace and not rely on Apple for assistance.
CHRP also uses industry-standard components, so the Mac makers (including Apple) have a wider choice of suppliers, can buy components at lower prices, and are less likely to be faced with a parts shortage. And CHRP allows the faster adoption of emerging technologies, such as the Universal Serial Bus and the FireWire high-speed peripheral bus, as well as of existing technologies that would give Mac owners more choices. For example, the CHRP specification supports the PC's ISA bus, which Mac makers could incorporate into their systems so Mac owners will be able to use any internal PC modem with their Macs.
The 233MHz and 266MHz StarMax Pro 6000 models will ship with 32MB of RAM, expandable to 1GB of EDO memory, and the 300MHz model will ship with 64MB, also expandable to 1GB. Thanks to its CHRP architecture, the Pro 6000 line can also use up to 96MB of synchronous DRAM (SDRAM), a faster type of RAM becoming prevalent in the PC market.
Motorola is providing an Ultra SCSI card to which you can connect devices at up to 40MBps, in addition to the Mac's standard 10MBps SCSI-2 connectors. A 100MB Zip drive is standard. Motorola plans to ship the systems with Mac OS 8 and not 7.6, contrary to several other news reports.