Explain ARM and Alpha please

[smp]

I'm not too familiar with these architectures, if someone could explain them to me.. thanks. I heard from someone that ARM is a much better architecture than x86, but I wasn't too clear on thier reasons. I did understand that they run cooler and are potentially capable of speeds as high as what we have, only that the instruction set is much more effecient, therefore faster? I know that ARM and Alpha are different, I also know that there are other architectures, if someone is familiar with this sort of thing, please let me know, I'm all curious about this stuff. Oh, and any other ones too, thanks..

 

[kylef]

ARM was designed by Acorn Computer (a British company) essentially from scratch in 1983-1985. The ARM1 was actually the first commercially available RISC microprocessor (the Berkeley RISC I was academic), but unfortunately the system in which it debuted was not completed until 1987 (the Acorn Archimedes). By that time other RISC platforms were available. Acorn Computer, VLSI Technologies, and Apple formed ARM Ltd. in 1991. Due to the small RISC core which utilized a relatively small number of transistors, the ARM chip was well suited for low power applications and embedded devices. The ARM instruction set is currently supported by 3 major operating systems: ARM Linux, MS PocketPC (WinCE), and EPOC (of Psion fame), all of which are targeted at small-scale, embedded applications.

The most famous device currently using an ARM processor is the Compaq iPaq, which uses a 206 MHz Intel StrongARM processor running the MS PocketPC operating system. This little processor consumes about 0.4 watts of power and is rated at about 700 MIPS. Intel renamed the processor (which it acquired from Digital Equipment Corporation in 1997) "XScale" in 2000 and now offers an entire product line based on this technology.

 

[smp]

Thanks for the informative reply...
But how come we're not seeing ARM in commercial PC's? And what about Alpha?

 

[AnoTech]

Well, I can't post a technically profficient synopsis like the other guy did, but
based off what he was saying..

It looks like supporting the ARM instruction set in a widely used O/S, just wasn't
in ARMs future. He also mentions it's performance @ low power. It looks like it
was engineered specifically for a "tiny" career.

Perhaps ideas used in the ARM creation might be applied to todays technology? Might
already be in the works...


ano

 

[kylef]

Since about 1992, ARM has always been targeted at the low-power, embedded market. The instruction set for many years was kept intentionally simple to keep the transistor count down to save power. The trend in desktop processors seems to be the opposite (more features in the instruction set). Also, it can't be stressed enough that people use whatever instruction set gives them the most access to software, and x86 has been by far the most dominant ISA in that regard. PowerPC, SPARC, and Alpha are probably the next 3 as far as software availability is concerned. In the embedded market, supporting legacy code hasn't traditionally been as important because there simply isn't that much code to begin with. And since ARM is the traditional instruction set for many embedded applications, it has an advantage there. It hasn't been until very recently that people have seriously considered running x86 code in embedded systems (e.g., Transmeta).

As for Alpha, I just read recently that Intel acquired the rights to the Alpha from Compaq. I don't really know much about the Alpha's instruction set architecture, other than it is a RISC architecture similar to MIPS. To be completely honest, Alphas had very good floating point performance but were NOT Mhz to Mhz faster than competing processors. The Alphas managed to get higher clock speeds (they beat everyone to 500 Mhz back in the day) by creating huge multi-stage pipelines, similar to what Intel is doing right now with the Pentium 4. They WERE "faster" in SPEC benchmarks than their competitors but not by a margin suggested by their clock speed advantage.

Note: the above statement regarding the relative performance of the Alpha is MY opinion, and is no doubt controversial. So please don't state it as fact when arguing with others about the relative benefits of different instruction set architectures unless you like living on the edge

 

[smp]

Thanks.. that was really in depth, appreciate it.

 

[Gunbuster]

If your really wacky you can get a ARM desktop Omega