IBM Corp’s PowerPC 615, said to be capable of emulating iAPX-86 processors in hardware, is running in the region of Pentium speeds, according to a report that will appear in next month’s edition of Computer Business Review. However, executives tell our sister publication that overall performance is being hampered by the time it takes the chip to switch between iAPX-86 emulation and PowerPC modes – a problem that also affects applications on Apple Computer Inc’s PowerPC-based Macs that include some emulated 68000 and some native code. Apple says that the mode-switching delay is such a problem that some parts of the operating system that could easily have been rewritten in native PowerPC code have been left in 68000 code because the mode-switching delay would more than cancel out the benefit of running native. The processor – widely, though unofficially dubbed the 615 – has been developed over the past year to emulate the iAPX-86 instruction set in hardware. It was not clear which PowerPC is being used, although some sources have indicated that the speed could have been achieved using a PowerPC 601-based part running at 132MHz. While the emulated performance is believed to be good enough for IBM to launch the chip commercially, should it wish to do so, an IBM source said that the technical problem over mode switching was so serious that IBM did not know what to do next. It slows it right down he said. Meanwhile, and despite repeated official denials, sources also indicate that IBM is continuing with its efforts to get the MVS instruction set onto the PowerPC. This work is believed to be being undertaken by the same group working on iAPX-86 emulation, in Burlington, Vermont. The work is now the responsibility of the newly formed Systems Technology Architecture Group, which handles all of IBM’s chip design efforts.
