ARMv7a architecture gets 40-bit addressing and virtualization support | Hacker News Reader

ARMv7a architecture gets 40-bit addressing and virtualization support

eetimes.com

8 pointswmf6 comments

Heres linus's take on it - "Paul (no@thanks.com) on 8/24/10 wrote: > >'ARM Ltd. announced extensions for virtualization and 40-bit >addressing to the ARMv7a architecture, two of the key new >aspects of ARM's upcoming Eagle core.' Oh gods. Please don't say that it's another PAE mess. It's a major pain, and having to specially map all the physical pages that you can't fit directly in the virtual address space leads to some nasty issues.

I hope they have a plan to move it towards a real 64-bit architecture. But it sounds like ARM is doing the whole "do all the mistakes x86 ever did" thing.

And the funny thing is, ARM people think that x86 is the ugly architecture. But with x86 cleaning its stuff up, and ARM apparently convinced it needs to do all the mistakes x86 did, we'll soon see ARM as the real cesspool.

                      Linus"

from http://realworldtech.com/forums/index.cfm?action=detail&...

Yeah, PAE wasn't a good idea when Intel did it in 1996 and it's not a good idea now for ARM, but Linux already has highmem support so I'm sure ARM highmem patches are imminent and people who need more than 4GB RAM will use them.

Still there's a good reason not to use 64 bits: interconnections, transistor count, die size. You can't have a CPU that sips milliwats of power and make an architecture of a 50 Watts beast.

But to the extent they want to compete with Intel and AMD in server space they're going to have to go all in to a full 64 bit design. What is the Eagle design for? Is there any other target market that needs a PAE half-measure like this?

Thank goodness some CPU designers have some common sense. There is no advantage whatsoever to 64 bit addressing. You are just pushing a bunch of zeros around forever. That's not to say 32 bit is enough. 40 bit shows the designers have some sense and aren't just pandering to ignorant masses who think that because 2*32 = 64 that means something.

Eh, not if involves using the equivalent of PAE. 40bit addressing in that requires applications to utilize a window to use memory. And pointers get invalidated when the window is moved. Hurrah for CPU designers shoving immense workloads onto the software devs, especially application programmers.

Reply on news.ycombinator.com