Intel's RISC-y Business 225
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?"
Re:finally??? (Score:4, Insightful)
Why we hate x86 (Score:4, Insightful)
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.
Hard to take the story seriously (Score:3, Insightful)
We live in a post-RISC world. Nearly every modern processor's "core" use the major innovations of a RISC chip. The size of the instruction set is of little importance; many so-called "RISC" architectures (such as Power) have a larger instruction set than the "CISC" x86_64.
The main issue that spawned the development of RISC (that instruction sets were getting so large and unwieldy that instruction decode would take the lion's share of a die's transistors) turned out to be less of a problem than anticipated. At the time, many CISC chips (VAX in particular) were implementing high-level programming features in the architecture's assembly language.
Nearly all of us have decided that efficient compilers have made a high-level, expressive assembly language unnecessary.
Another factor is that modern processors are superscalar, with multiple execution pipelines per core - one instruction decoder then feeds several pipelines, which further reduces the relative size of the instruction decode.
However, modern chips do implement (at least internally), other "core" ideals of the RISC processor:
- Numerous registers
- Load/Store memory access
- Multi-stage Pipelines
- One instruction per clock tick (ie. keep the complexity of an instruction down to what can execute in one tick - if something takes more than one tick, break it down into smaller pieces).
The one thing that the so-called "RISC" chips have historically been known for is dependability: The machines that use them don't crash. This requires more than just a good CPU: It requires good hardware in general, and a good operating system. The "RISC" vendors - such as Sun (now Oracle), IBM, HP and SGI, control the quality of the entire system - from the electrical components, to the chassis, to the airflow in the chassis. Even the datacenter's abilities (power, cooling capacity, airflow) are specified.
There are a lot of things that go into making a system that's mission-critical, and the CPU is a small part of the equation (and usually is the least troublesome). Putting an CPU on a motherboard doesn't give me guarantees about airflow, power reliability, I/O stability and speed, vibration tolerance, nonblocking I/O, and reliability - to say nothing about core OS stability.
Intel isn't interested in doing anything other than selling chips. Unless Intel is willing to take upon themselves a whole-system approach - covering everything from the chassis, cooling and airflow, power supply, motherboard, and core operating system - they'll never play in the league.
Making a mission-critical system is left to others who use Intel's chips, such as HP's high-end Itanium line, and SGI's Altix and Altix UV systems (using Itanium and x86_64).
Re:Itaniums is **NOT** RISC (Score:4, Insightful)
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?