Wikipedia says [malarkey] again...

[BigEd]

Thanks for the pointer to the paper - there's a version at http://www.inf.fu-berlin.de/lehre/WS94/RA/RISC-9.html which is more legible for text (but not for the images). It's a pity that ARM wasn't on their radar.

I'll concede the LDM/STM. I think the delayed branches is a red herring - which is to say, in my view it's not an interesting critical property. I accept that I'm deviating from Patterson and that he coined the term and started the revolution!

As for number of addressing modes not being one, I think that might be a red herring. The important point here, in my view, is that there should not be any expensive addressing modes - for example, indirect modes.

The crucially practical points would, in my view, be:
- cheap implementation should be possible
- enough additional clock speed from the simple implementation to compensate for the lack of complex instructions
- easy compiler target

(As we both know, high-performance implementations become complex and are not cheap: the crucial point is that a simple implementation is sufficiently performant.)

Cheers
Ed

[Aaendi]

Do addressing modes have anything thing to do with RISC vs CISC? I noticed that ARM barely has any addressing modes, and they're all variations of register indirect.

[TMorita]

Aaendi wrote:

Do addressing modes have anything thing to do with RISC vs CISC? I noticed that ARM barely has any addressing modes, and they're all variations of register indirect.

Broadly speaking, most RISC processors only have one memory addressing mode, excluding multiprocessor synchronization primitives such as load-link/store-conditional.

AArch32 has two: LD/ST, and LDM/STM.

In a previous message, I explained why LDM/STM are not very RISC-like.

Toshi