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Intel's RISC-y Business
Esther Schindler writes "With the Xeon 7600 line, Intel is finally using the 'R' word: RISC. With the new chips, Intel is targeting the mission-critical market dominated by Sun SPARC and IBM Power, a first. Can the Xeon E7 processor deliver Intel's final blow to the RISC market, which includes its own Itanium? 'With the launch of the E7 earlier this year, it seemed Intel was finally ready to make its final push, calling out RISC by name. "The days of IT organizations being forced to deploy expensive, closed RISC architectures for mission-critical applications are nearing an end," said Kirk Skaugen, vice president and general manager of Intel's Data Center Group, in a statement announcing the E7 line. Bold words.' Andy Patrizio interviews several experts; what do you think?"
A non-entity outside a few X terminals and RAID controllers.
I've always been curious about this kind of statement. I hear it a lot. While I understand the complexities of silicon implementation (finding instruction lengths and decode are a PITA), I've always thought the ISA itself was rather elegant. Yes, there is cruft that could be dropped and AMD did some of that with X86-64, but overall, the day-to-day instruction set is mostly orthogonal and has a fairly regular encoding. GPR shifts, MUL and DIV are a bit quirky and the lack of a packed 64-bit integer multiply is an almost unforgivable sin, but overall, I rather like it.
What are the things you would like to see changed? We need specifics to have an interesting discussion. :)
Limited number of registers
Instructions that require certain registers or a certain subset of the registers
No three register operations. This impacts pipelining because it is not possible not overwrite one of the source registers.
Variable instruction length makes decode a headache
Lots of really bad stuff that isn't used much by modern code by still must be maintained for compatiblity: segments, 286 protection, IO instructions, etc.
I've wondered sometime what attitudes would be if a more likable contemporary instruction set had won. VAX and 68000, for instance, are much more palatable to program but they have performance flaws that are probably worse than x86.
As far as x86-64 goes, isn't that mainly because AMD trotted out a 64bit processor that was backwards compatible with 32bit programs and whomped Intel's 64bit processors which required specially compiled programs to work with?