IBM officially unveiled the company’s new PowerPC processor at the Microprocessor Forum on Monday. While IBM would not confirm that Apple could be a customer for the new chip, analysts continue to see the potential for the chip in Macs.
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Microprocessor Report senior analyst Tom Halfhill sees Apple as an obvious potential customer for the PowerPC processor announced Monday by IBM.
“They can’t say Apple, but we can,” Halfhill told MacCentral Tuesday at the Microprocessor Forum. “Speculatively of course.”
Peter Sandon, senior PowerPC architect at IBM, remained quiet on specifics about potential customers for the new processor. But, he gave no reasons why the new PowerPC 970 couldn’t be used in a Macintosh and plenty of reasons why it could.
The PowerPC 970 is adapted from IBM’s successful Power4 server processor. The big differences between the PowerPC 970 and IBM’s PowerPC 750 family — known to Mac users as G3s — are that the PowerPC 970 includes a vector processing unit, a far deeper instruction pipeline, far higher clock speed, a high bandwidth memory bus and, most importantly, 64-bit processing.
“While many are doing very well developing 32-bit processors,” Sandon said, “we feel that developing a 64-bit processor with 32-bit compatibility will enable more applications to take advantage of 64-bit operation.”
Put simply, 64-bit processing allows a processor to work on more data with each clock cycle. Sandon said that another advantage from 64-bit operation is the ability to add more than 4GB of RAM to a system. However, code must be created specifically for 64-bit operation to see an advantage.
The PowerPC historically has been a 32-bit processor, and the vast majority of code created for it, including the Macintosh OS and applications, are 32-bit code.
IBM made its way around this problem by adding a 32-bit native mode to the processor that essentially changes the PowerPC 970’s instruction registers, allowing it to run as a 32-bit processor. Sandon stressed that this was not any sort of emulation.
“All 32-bit applications can run as is on the 970,” Sandon said. “Changes are needed to make a 32-bit OS run on the 970, but the list of changes is small.”
Sandon said that IBM has a 64-bit version and a 32-bit version of Linux running on the PowerPC 970 in the lab.
Halfhill gave a little history about previous three abortive forays by PowerPC into the 64-bit realm in the mid 1990’s.
“The history is not very stellar,” Halfhill said, “but they’re going to try again.”
Halfhill noted that he brought up the history to show that the PowerPC has always had a 64-bit instruction subset that has been rarely used. Moreover, the PowerPC processor family has included rules governing 32-bit and 64-bit processing from the beginning.
Halfhill added that it might be no coincidence that IBM and AMD are both developing 64-bit processors.
The PowerPC 970 brings a Single Instruction Multiple Data processing unit to IBM’s side of the PowerPC house. Motorola first added this feature, called AltiVec to the G4.
Sandon said that the SIMD unit on the PowerPC 970 uses the same set of 162 instructions that Motorola’s AltiVec uses. This means that applications optimized for AltiVec will perform normally on the PowerPC 970. Halfhill added that all applications optimized for AltiVec on the Macintosh should see performance boosts on the PowerPC 970, if it indeed is used by Apple.
“From my analysis,” Halfhill said, “it (IBM’s SIMD) is virtually compatible (with AltiVec). Why would IBM add this if it wasn’t for Apple?”
The PowerPC 970 is “Book E” compatible, meaning that it takes instructions from the set most recently agreed upon between Motorola and IBM for compatibility.
Sandon said that the PowerPC 970’s design is adapted from IBM’s successful Power4 server processor. Physically smaller, the PowerPC 970 sacrifices some execution units — including the Power4’s second processor core — for 64-bit compatibility and the SIMD unit.
While the Power4 core has two processor cores and massive caches for MP implementations, the PowerPC 970 has only one processor core, an SIMD unit and a 512K on-die L2 cache. The cache includes error correction. The PowerPC 970, as described today, has no connectors for an L3 cache.
The new processor also has a 64K L1 instruction cache and a 32K L1 data cache.
The PowerPC 970 has a much deeper instruction pipeline, allowing the PowerPC 970 to operate at higher frequencies.
Where the Power4 operates at 1GHz, the PowerPC 970 will run between 1.4GHz and 1.8GHz — the fastest Motorola G4 operates at 1.25GHz.
The PowerPC 970 will be manufactured using IBM’s 0.13-micron copper manufacturing process coupled with IBM’s Silicon on Insulator technology. SOI allows the gates of the transistors on the processor to operate more efficiently, allowing the processor to operate at higher frequencies using less power and generating less heat. The Power4 is produced using IBM’s older 0.18-micron copper process.
At 1.8GHz, the PowerPC 970 will consume 1.3-volts and dissipate 42-Watts. At 1.2 GHz, the PowerPC 970 will consume 1.1-volts and dissipate only 19-Watts. For comparison, a 1GHz G4 consumes 1.6-volts and dissipates 21.3-Watts.
Sandon said that the PowerPC 970 has 52 million transistors, compared to 33 million on the latest G4s from Motorola.
The PowerPC 970 will also support a high bandwidth memory bus, potentially running at up to 900MHz. Sandon said that this achieves a theoretical memory bandwidth of 7.2 GB/Sec., but with overhead this is reduced to 6.4 GB/Sec.
Microprocessor Report editor in chief Peter Glaskowsky said that the PowerPC 970’s memory architecture is proprietary. One of the hurdles that Apple would have to jump to use IBM’s latest processor would be to design a memory controller for the part.
Apple typically designs their own memory controllers, and Glaskowsky said that this would not be a barrier for Apple if the company were committed to using the PowerPC 970.
The PowerPC 970 is estimated to outperform the Power4 at 1.8GHz, generating 18 million RC5 keys a second. For those addicted to SPECint 2000 benchmarks, the PowerPC 970 is estimated to produce 937 at 1.8 GHz.
Sandon said the IBM lab has PowerPC 970 samples today. He expects the PowerPC 970 to sample to customers by the second quarter of 2003, with the processor expected to enter production in the second half of 2003.