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ARM as a desktop processor
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Clinically Insane
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Mar 15, 2010, 01:16 PM
 
I'm probably doing the math wrong, but according to ARM, their A8 processor consumes only 300mW, and are guaranteed to not exceed 700mW; this is at 1GHz.

The latest "Extreme" Core i7 consumes over 350W during peak performance; so that means the ARM A8 is roughly 500 times more power efficient.

So you could have 500 1GHz ARM processors consuming no more power than an 8 processor Core i7 running at 4GHz per core.

Seems like a good idea to me, assuming they can shrink the ARM core and fit 500 of them in a computer.
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Mar 15, 2010, 01:21 PM
 
I think we'll start to see ARM make it to the desktop if the new 'Smartbook' category catches on. I, for one, hope it does and am thinking about getting an AlwaysInnovating Touch Book (though I'd like to see them update the hardware first); 10 hours of battery life! If Smartbooks catch on, then people will get used to the software that runs on them (not Windows other than Windows Mobile), and maybe it will make it to the Desktop.

Apple is actually probably in the best position to do this as they've already got OS X running on ARM.
     
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Mar 15, 2010, 01:31 PM
 
I tend to prefer using my legs for that kind of power. But maybe that means I need to do more pushups?
     
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Mar 15, 2010, 01:40 PM
 
Wow, that was pretty awful.
     
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Mar 15, 2010, 02:35 PM
 
Yeah, shame on you Oisin. I expected something more poetic.
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Mar 15, 2010, 03:08 PM
 
Not sure I could handle yet another architecture shift from Intel to ARM. Would be amusing to go back to a RISC based architecture.
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Mar 15, 2010, 03:17 PM
 
Originally Posted by olePigeon View Post
The latest "Extreme" Core i7 consumes over 350W during peak performance; so that means the ARM A8 is roughly 500 times more power efficient.
Where'd you get that figure from? An entire i7 980X system at full tilt consumes just 170W.

Also it's not 500 times more power efficient since it's not doing the same amount of work at 700mW as the i7 is doing at 100W. It's just smaller and less capable.

Why don't we use hundreds of ARM cores? Single threaded performance. Even a lot of things that are considered to scale well (like H.264 encoding) on current chips are using tricks/shortcuts that only work up to about 20 cores.
( Last edited by mduell; Mar 15, 2010 at 04:29 PM. )
     
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Mar 15, 2010, 03:22 PM
 
Originally Posted by The Final Dakar View Post
Wow, that was pretty awful.
Apologies. I was on my way out the door and in a hurry.

It won’t happen again. Until next time, that is.
     
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Mar 15, 2010, 04:44 PM
 
Originally Posted by mduell View Post
Where'd you get that figure from? An entire i7 980X system at full tilt consumes just 170W.
Intel's Core i7 processors - The Tech Report - Page 14 (I guess that could be the whole computer and not just the CPU?)

Originally Posted by mduell View Post
Also it's not 500 times more power efficient since it's not doing the same amount of work at 700mW as the i7 is doing at 100W. It's just smaller and less capable.
That'd be an interesting test if you could underclock an i7 to 1GHz and pit it against an ARM processor. I don't know enough about their respective technologies to make an informed opinion on it, so I'll trust your judgment.

Originally Posted by mduell View Post
Why don't we use hundreds of ARM cores? Single threaded performance. Even a lot of things that are considered to scale well (like H.264 encoding) on current chips are using tricks/shortcuts that only work up to about 20 cores.
Sounds like a software limitation. Wouldn't be a problem with BeOS.
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Mar 15, 2010, 06:37 PM
 
I wonder what chip real estate would be required for 200 ARM processors, as compared to a single desktop Intel chip. I also wonder what the cost difference would be.
     
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Mar 15, 2010, 07:45 PM
 
@olePigeon
Actually, you can buy ARM `desktops' today for as little as $100. If you want more connectivity, you have to spend $250. They contain 512 MB RAM and you can plug in either harddrives or use SD cards for storage.

Of course these plug computers are designed to function as micro servers, e. g. you could build your own router/firewall or NAS. Since they run Linux (or FreeBSD apparently), you can also create RAID by connecting them to external enclosures via eSATA, for instance.

To answer your questions: desktop apps typically need single-core performance and no, `BeOS' wouldn't really change that. I suppose you could use ARM cpus in supercomputer environments (the PowerPC 450 used by IBM also started out as an embedded processor and is still used as such). These machines, however, have workloads that are easily parallelizable. This is not true for desktop apps.

Regarding ARM on `desktops,' the main obstacle, obviously, is the lack of Windows support. Top notch ARM cpu designs are approximately on par, performance-wise, with Intel Atoms. I'm fairly certain Intel Atoms wouldn't be popular at all if it weren't for the lack of Windows support: they're more expensive, consume much more power (especially if you add the chipset) while having comparable performance. In a sense, ARM cpus have just gotten `fast enough' for main stream computing.
Originally Posted by Eug View Post
I wonder what chip real estate would be required for 200 ARM processors, as compared to a single desktop Intel chip. I also wonder what the cost difference would be.
That depends on the exact ARM core you're thinking of: the (rather primitive) Cortex M1 (which is designed to make 8 bit (!) cpus obsolete) has 12,000 gates. This means, the Cortex M1 consists of roughly 50,000 transistors.

By comparison, a Core 2 Duo has at least 291 million transistors -- that's a difference of three orders of magnitude.
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Mar 16, 2010, 12:27 AM
 
Originally Posted by olePigeon View Post
Sounds like a software limitation. Wouldn't be a problem with BeOS.
Haiku is an open source implementation of BeOS. It could be compiled for ARM if necessary.
     
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Mar 16, 2010, 02:38 AM
 
Originally Posted by olePigeon View Post
Intel's Core i7 processors - The Tech Report - Page 14 (I guess that could be the whole computer and not just the CPU?)
That's 275W for their system. Per the Anandtech article the CPU maxes out at about 135W.

Originally Posted by olePigeon View Post
That'd be an interesting test if you could underclock an i7 to 1GHz and pit it against an ARM processor. I don't know enough about their respective technologies to make an informed opinion on it, so I'll trust your judgment.
Blow the ever living snot out of it. It would also massively reduce the power consumption of the i7.

Originally Posted by olePigeon View Post
[Sounds like a software limitation. Wouldn't be a problem with BeOS.
It's an algorithmic limitation. BeOS isn't magically going to make the algorithm scale better.

Originally Posted by Eug View Post
I wonder what chip real estate would be required for 200 ARM processors, as compared to a single desktop Intel chip. I also wonder what the cost difference would be.
Cortex A8 is about 4 mm^2 on a 65nm process with L1 and L2 cache. Westmere-6C is about 240 mm^2 on a 32nm process but it's half uncore (connections and L3 cache) so each core is about 20 mm^2 with L1 and L2 cache. So one Westmere core is about the size of ~20 ARM cores on the same process size.

200 ARM cores would be un-fab-ably large even on a 45nm process (400 mm^2 plus interconnects is well over 600 mm^2). Even in the gigantic GPU chips with their lower clockrates and often dismal yields are only ~400 mm^2.
     
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Mar 16, 2010, 04:32 AM
 
It's weird how we went from desktop vs workstation to all desktops having workstation(or close) power. And now we're moving to lower performance and simpler processors for the desktop/laptop.

I wonder if the power in most high end processors are better off in servers/graphics workstation class computers, something most average users probably don't need.

Personally i wonder if having a single 'workstation' class computer per household and multiple thin clients(ala iPad) all running on a VPN served up by the 'workstation' ? or some other hierachy ?

To be completely honest, the 'heaviest' lifting i do on my Mac is compiling projects and encoding video and some image editing.

To me, performance has passed a point where i see value in more(at least in desktops and laptops).. it happened almost 3 years ago with the intel iMacs. Maybe a move to blue ray or some other performance heavy function would validate these powerful machines ?

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Mar 16, 2010, 08:38 AM
 
It would be cool to see an ARM running classic Mac OS (9, 8, 7, whatever).

Remember, we used to used processors slower than 500MHz on desktops every day before 2000.

A desktop doesn't need to be a workstation (multi-core, super-computer 3D rendering machines). For video, email, and surfing, how much processor does one really need? If our OS vendors dropped all the eye-candy and processor-wasting crap from their OSes, we wouldn't complain.
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Mar 16, 2010, 08:47 AM
 
arstechnica has a nice article on this: it explains rather well why building cpus with excellent single thread performance is hard and why you wouldn't end up with something a lot more efficient if you used an ARM-based cpu instead.

While ARM cpus are more efficient than Atoms at similar performance levels, I haven't seen plans of ARM to evolve beyond their core markets. This is good. There is no reason we should use one architecture for everything. I'd rather have two, three architectures that do what they're supposed to do well than one that tries to do everything. However, it may very well be that for some part of the market (think MacBooks, AppleTVs and Mac minis), an ARM cpu has enough processing power to satisfy the needs of the customers. Then, however, customers will have to use the iPhone OS -- an OS that by design is focussed on `single-tasking*' rather than extensive multitasking.

* I know that the underlying OS has no problem to multitask. But up until now most apps can't run in the background. iPhone OS 4.0 is rumored to bring multitasking to the iPhone OS, but we'll have to see if that turns out to be true. Even if it does, I think I won't have 20-30 simultaneous windows open at the same time as I frequently do on my main machine.
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Mar 17, 2010, 08:22 AM
 
I was embarking on an experiment before Apple announced the iPad. i wanted to get a Mac from the early 90s (MacOS7-ish) and see if it could accomplish everything i needed from a computer (with the exception of high-end gaming and video encoding obviously), on it. Apart from the single processor and low RAm, the OS was tiny by todays standards.

Intel and AMD just announced processors with even more cores....and i actually couldn't care less about that benchmark/metric/measure anymore.
     
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Mar 18, 2010, 06:25 PM
 
MIPS per Rupee still matters. Intel beats them all in this respect.
     
   
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