RISC

gdea73

I thought the concept of a RISC-based microarchiteture was cool, especially if it meant that its assembly would be far simpler and better optimized.

Though as far as I know RISC machines are only used for highly specialized applications. Which makes sense, as not only would they run different operating systems but their entire architecture is completely incompatible with Intel's x86. That being said, is it possible to obtain or build a computer with a RISC CPU just to mess around with?

Just thought it might be cool. My knowledge on RISC, as well as either x86 or RISC assembly, is admittedly limited, just haphazardly wanted to learn about it.

This summer if I have any time at all I plan on learning to develop applications, not necessarily for RISC because that'd be sort of useless, but to learn an actual programming language would be beneficial to my understanding of software and stuff. I'd like to learn Java, perhaps, or C.

But in the meantime I have unrelated busywork to do. And a crapton of it. Wonderful.

noone

Speaking of RISC architectures, the Nintendo 64 has a RISC processor if I recall. Kind of a shame, it had decent processing ability in comparison to its competitors, but sucked in every other aspect.

DeepFriedCookies

noone wrote:

Speaking of RISC architectures, the Nintendo 64 has a RISC processor if I recall. Kind of a shame, it had decent processing ability in comparison to its competitors, but sucked in every other aspect.

MIPS, actually. Multiple computer systems also had that, including servers from Compaq and SGI.

gdea73 wrote:

I thought the concept of a RISC-based microarchiteture was cool, especially if it meant that its assembly would be far simpler and better optimized.

Though as far as I know RISC machines are only used for highly specialized applications. Which makes sense, as not only would they run different operating systems but their entire architecture is completely incompatible with Intel's x86. That being said, is it possible to obtain or build a computer with a RISC CPU just to mess around with?

Just thought it might be cool. My knowledge on RISC, as well as either x86 or RISC assembly, is admittedly limited, just haphazardly wanted to learn about it.

This summer if I have any time at all I plan on learning to develop applications, not necessarily for RISC because that'd be sort of useless, but to learn an actual programming language would be beneficial to my understanding of software and stuff. I'd like to learn Java, perhaps, or C.

But in the meantime I have unrelated busywork to do. And a crapton of it. Wonderful.

PowerPC, ARM, MIPS, Power, Alpha, SPARC.. all of these are RISC processors. Intel's x86 also takes some manufacturing cues from RISC nowadays. RISC is good for low power nowadays, and it was good for the evolutions it gave the computer industry, but it's basically obsolete. I mean, if the system is doing a single dedicated task, RISC would make a better choice, but CISC became most popular choice for desktop workstations for a reason.

nightice

RISC is a philosophy, not an architecture. The lines between RISC and CISC have blurred somewhat over the years as the notion of what a general-purpose computer is has evolved. The best example you can see of that is in supercomputers - Cray's stuff in the 80s was all about quickly executing programs, for example, to the point where technicians would adjust wire lengths inside the computer by millimeters to retain the designed performance characteristics. There was a pretty massive paradigm shift in the late 90s to distributed computing on commodity hardware, agnostic of architecture, once the performance walls of "just make it faster" became more obvious. Sure there's room for performance improvement (clock speed, power consumption, increasing on-die cores and cache), but fundamentally there's only so many ways to implement a CPU. It's just cheaper to distribute your calculations nowadays and reap the absolutely obscene benefits of many machines working in parallel.

At the opposite end of that spectrum are microcontrollers used in embedded devices - we're talking 4 MHz and 128KB each of program and working space. That's sortof-kindof what the above poster was getting at with "a single dedicated task", the use case for a PIC or MSP430 is so vastly different that there are very good reasons to keep the CPU implementation as trivial as possible. Probably the same with DSPs, I guess, but I don't know enough about those to comment.

gdea73

wow I appreciate the enthusiasm with which you fill me in on the history of the RISC philosophy. Interesting how it all played out. I guess previously the way RISC was described I thought it would be superior to CISC, but I see this isn't necessarily the case. Forgot about MIPS, believe TiVo uses it, otherwise that's all I know.

stitch

Guest wrote:

PowerPC, ARM, MIPS, Power, Alpha, SPARC.. all of these are RISC processors. Intel's x86 also takes some manufacturing cues from RISC nowadays. RISC is good for low power nowadays, and it was good for the evolutions it gave the computer industry, but it's basically obsolete. I mean, if the system is doing a single dedicated task, RISC would make a better choice, but CISC became most popular choice for desktop workstations for a reason.

Sony's Cell processors in the PS3... Broadway in the Wii, the chip in the 360, all your iDevices and Androids, IBM Watson's massive use of POWER7 chips? I'd say it's hardly obsolete, it's just not found too much in the personal computing segment anymore since Apple dropped use of PowerPC back in 05.

DeepFriedCookies

stitch wrote:

Guest wrote:

PowerPC, ARM, MIPS, Power, Alpha, SPARC.. all of these are RISC processors. Intel's x86 also takes some manufacturing cues from RISC nowadays. RISC is good for low power nowadays, and it was good for the evolutions it gave the computer industry, but it's basically obsolete. I mean, if the system is doing a single dedicated task, RISC would make a better choice, but CISC became most popular choice for desktop workstations for a reason.

Sony's Cell processors in the PS3... Broadway in the Wii, the chip in the 360, all your iDevices and Androids, IBM Watson's massive use of POWER7 chips? I'd say it's hardly obsolete, it's just not found too much in the personal computing segment anymore since Apple dropped use of PowerPC back in 05.

Very true. But mostly because it's very power efficient. ARM uses almost a quarter of the power of an x86 chip, for example.. It's less RISC being superior, and more it being superior at the task it's handed. Desktops, laptops, anything running a multipurpose OS really benefits from CISC, but anything dedicated to a single task (Even including Watson, as amazing as it is) can really get an edge by using a RISC chip.

Basically there's a time and a place for everything, and although I don't think a truly RISC chip is a great idea for a desktop workstation, it still has it's place.

Anonymous

Almost all CPUs are RISC aside from x86. Motorola 68k and VAX (non-x86 CISC) have almost dwindled to non-existance. Given the complexity of decoding modern x86-64 instructions and the necessity to do so and push the micro-ops to the appropriate execution units, almost half of the logic area on the chip is the decode unit. Makes you feel kind of cheated? At least 80% of the die is memory (cache). So with RISC chips of similar die area, you'd get almost twice the logic (decode still isn't free) or you could reduce power consumption drastically. This is how modern ARM, MIPS, PPC, etc chips get far superior performance per watt.