ARM CPU's

[kilo_17]

So, I've seen all this stuff lately about ARM CPU's, and was wondering what exactly is it? Will it make it's way into desktops? Is it better than modern AMD and Intel CPU's? Thanks for all your advice

 

[hunter315]

ARM CPUs are for mobile devices, they specialize in low power consumption and high performance/watt ratios. They are a different architecture style, they arent x86-64 like most desktop and laptop chips are so many of their techniques are necessarily applicable because once you get up to a larger size its no longer the most efficient way to do it, an ARM CPU could never handle doing large scale double precision number crunching like a desktop CPU could, but it also doesnt blow through power like a desktop CPU would.

 

[kilo_17]

So, ARM CPU's probably wouldn't make it to the desktop PC's, and are better for mobile devices? And a desktop CPU would perform better than an ARM CPU scaled to a larger size?

 

[jprahman]

A big advantage of ARM at the instruction set level is that ARM instructions are simpler than X86 instructions, as a result ARM chips use fewer transistors and are smaller. Because of the advantages of a RISC-based instruction set (the same type ARM uses), modern X86 processors internally use RISC instructions, however in order to accomplish this a large amount of decoding hardware must be employed. All the decoding hardware than modern X86 processors must use add up to a lot of heat output and power consumption.

I personally think that ARM CPUs in the future could rival X86 in raw performance. One reason they haven't overtaken X86 so far is that they've been held back to this point because all applications of ARM CPUs have been in embedded/ mobile applications where low power is a necessity. As a result the ARM chips to date haven't been very high performance compared to X86.

Once ARM designers get cut loose from the low power/ low heat restrictions and get a bump in their transistor budget I have a feeling that we'll see ARM chips that have the potential to become standard desktop CPUs comparable to what we have now.

After all the most powerful CPUs offered by the likes of IBM use the same RISC philosophy that ARM does, they just run much hotter and use more transistors. As to the floating point issue, ARM processors could be given additional vector processing instructions similar to AVX that would allow for better floating point performance.

 

[jprahman]

I have to add that an another barrier to the introduction of ARM CPUs in the market traditionally dominated by Windows is that first a OS that supports ARM must be released (Linux already does but it isn't widely used), and then programs must be compiled to run on ARM CPUs. The second step isn't a huge issue, usually involving changing a few compiler switches and rewriting small amounts of CPU specific code in a select few cases. The first issue is the biggest, right now Windows doesn't run on ARM, so first Microsoft will have to release a version of Windows that runs on ARM. Fortunately Windows 8 is reportedly going to have ARM support.

 

[palladin9479]

On x86 CPU's the decoding hardware is actually very very small. The largest part of the x86 CPU is the superfluous amounts of L2 (now L3) cache that Intel / AMD put on it, sometimes as much as 50% of the die space is nothing by cache.

ARM isn't a CPU, its an architecture. Any company can contact ARM and license the architecture and produce their own ARM based CPU from it. This allows an amazing level of refinement and specialization to whatever task the CPU is needed for.

 

[megamanx00]

There have been desktops with ARM CPUs. In fact, the ARM architecture was originally developed for Acorn Computers. The company spun off ARM holdings to license ARM architecture to others

http://en.wikipedia.org/wiki/Acorn_Computers

In some ways ARM is more efficient than x86 CPUs by Intel and AMD simply because of the nature of the x86 instruction set. It's one of the reasons that both companies have agreed to phase out older instructions that are no longer widely used. Modern CPUs are actually more like RISC CPUs with hardware instruction decoders that turn x86 instructions into ones they can use.

 

[kilo_17]

So then what exactly is x86?

 

[loneninja]

So then what exactly is x86?

Instruction set Intel created long ago, and own all rights too. AMD and VIA are the only two licensed to produce x86 compatible chips, and Windows along with the majority of modern software is designed to run on the X86 instruction set.

 

[kilo_17]

Sorry for all the questions, but what does the instruction set do? And why would Intel license x86 to AMD when AMD is a huge competitor?

 

[saaiello]

An instruction set, or instruction set architecture (ISA), is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O. An ISA includes a specification of the set of opcodes (machine language), and the native commands implemented by a particular processor.

Instruction set architecture is distinguished from the microarchitecture, which is the set of processor design techniques used to implement the instruction set. Computers with different microarchitectures can share a common instruction set. For example, the Intel Pentium and the AMD Athlon implement nearly identical versions of the x86 instruction set, but have radically different internal designs.

http://en.wikipedia.org/wiki/Instruction_set

Intel Legal crapola
http://jolt.law.harvard.edu/digest/patent/intel-and-the-x86-architecture-a-legal-perspective-2

Google and Wiki are really good you should try them.

 

[kilo_17]

Best answer selected by kilo_17.