A microprocessor developed by IBM that that included logic for decoding x86 instructions into PowerPC-native instructions. The idea was to create a computer that would be able to run PowerPC applications, as well as Windows and DOS applications at near-native speeds. The chip was announced in Q4 1994 (Chiplist), and was killed late in its development in 1996 (ComputerGram). Not a whole lot of information about the chip is available on the Internet nowadays, but here are some various snippets (with varying degrees of credibility) that I scavenged:
- The logic for translating x86 instructions would likely reside in a coprocessor. If Intel decided to sue IBM, IBM could still sell PowerPC 615 motherboards without the coprocessor (BYTE).
- The chip would be pin-compatible with the Intel OverDrive sockets (Chiplist).
- The chip would have 64-bit instructions in addition to 32-bit instructions, like the 620 (VLSI).
- It would take five clock cycles to switch between x86 and PowerPC modes (VLSI).
- The chip was based on the PowerPC 604 (Code Names).
I found site mentioning the existence of a PowerPC 616, and another site mentioning a PPC/x86 hybrid processor with the code name Merlin (RISC Processors, Code Names). It was supposedly based on the 603, and developed by Somerset.
Many of the engineers that worked on the PowerPC 615 project were later hired by Transmeta to develop a new x86 based chip (the Crusoe).
References
- "An 80x86-Compatible PowerPC?" BYTE Magaine. June 1994.
<http://www.byte.com/art/9406/sec6/art6.htm>.
- Chiplist
<http://ce.et.tudelft.nl/~offerman/cl.2.64.8.html>.
- "Code Names Uncovered: Prozessoren."
<http://www.cupertino.de/pages/archiv/CodeNames/Processors.html>.
- RISC Processors.
<www.volny.cz/v.reif/risc2.htm>.
- "The circuit and physical design of the POWER4 microprocessor."
<http://www.research.ibm.com/journal/rd/461/warnock.html>.
- VLSI Microprocessors - A Guide to High-Performance Microprocessor Resources.
<http://www.fh-augsburg.de/informatik/professoren/maertin/rechnerarchitekturen/anhang/literatur/Allgemein/www2.ssd.sscc.ru/>.
- "Will Transmeta revive IBM's PowerPC 615?" Computergram International.
<http://www.findarticles.com/cf_dls/m0CGN/n196/21189735/p1/article.jhtml>.