ARM Launches Cortex-A5 Processor, To Take On Atom

bigwophh writes "ARM launched its new Cortex-A5 processor (codenamed Sparrow) this week, and while it's not targeted at the top end of the mobile market, it is a significant launch nonetheless. The Cortex-A5, which will likely battle future iterations of Intel's Atom for market share, is an important step forward for ARM for several reasons. First, it's significantly more efficient to build than the company's older ARM1176JZ(F)-S, while simultaneously outperforming the ARM926EJ-S. The Cortex-A5, however, is more than just a faster ARM processor. Architecturally, it's identical to the more advanced Cortex-A9, and it supports the same features as that part as well. This flexibility is designed to give product developers and manufacturers access to a fully backwards-compatible processor with better thermal and performance characteristics than the previous generation."

Comments

Summary is misleading

[fnj]

The Cortex-A5 is aimed at phones. The Cortext-A9 is the one aimed at netbooks. The article referenced in the summary makes this clear.

No, it's not...

[Anonymous Coward]

The Cortex-A5 is a slight improvement over the MPCore/Arm11/Arm9. That's nice for those who need it, but it's miles away from the speed of a Cortex-A9, which is really what's going to be needed to battle Atom.

And since the A9 has announced by ARM quite some time ago, this posting should have been written then not now.

In reality, it's not clear which niche the A5 is going to occupy. It's probably going to be useful in lower end smartphones only, since current higher end models are already using the faster A8.

Re:No, it's not...

[Locutus]

the Cortex-A8 is out now on the 65nm process as are all the other low power device CPU's except Atom. Atom is currently on 45nm to get in the ballpark as the others but power usage is still pretty high. Cortex-A8 on 45nm should be in the pipeline soon and along with it, Cortex-A9. Those are going to shack the Atom up on price/watt and performance/watt. This is why Intel is moving Atom to 32nm ASAP but it's very expensive for them because they have to price the Atom low while at the same time use very expensive 32nm process space which they normally use for high profit desktop/server CPUs. So in 2011, along comes Cortex-A5 on 40nm so Intel would have to start looking at 2?nm processes to keep competing. I believe the ARM dude talks about this somewhat.

Size is a big deal and right now, Cortex-A8 on 65nm is rather large for smart phones. they pack some decent power for netbooks so I'm not sure what the delay is on that front. Cortex-A9 on netbooks would be very nice but I think they are just sampling now so it won't happen til next year( 2010 ).

ARM is a thorn in both Microsoft and Intel's sides and there is probably massive amounts of pressure on OEMs and manufacturers to stay away from it. Atleast on the netbook side. Remember, the head of the Thai Manufacturers Association said they fear Microsoft when talking about Linux on netbooks. ARM is an enabler for Linux so it too is a threat to Microsoft. But I sure hope the market gets to make the choice some how, some way.

LoB

Good news for future iphone

[not-enough-info]

Looks like the Cortex-A5 has 50% more performance while using 1/3rd the power of the current generation ARM11 found in the iPhone. As a game developer this makes me hopeful that we'll see cellphones as a gaming platform without sacrificing useful battery life.

Re:Good news for future iphone

[TheRaven64]

If it's not superscalar, why does it need a branch predictor? It only needs to know when the first instruction fails a cache hit, so that any results can be held.

Uh, what? You need a branch predictor because it's pipelined. It has an 8-stage pipeline, which means that it doesn't know the result of an instruction until eight cycles after it was issued. If you come to a conditional branch, you need to decide whether to take it or not. For example, if you have some C code saying something like 'if (a == 12)' then you can't decide whether to jump to the else block until you've computed the value of a, which will be 8 cycles in the future. Without a branch predictor, you just stall for 8 cycles and do nothing. Given that compiled code averages about one branch every 7 instructions, that means that you would be spending most of your time doing nothing.

The branch predictor makes a guess about which branch to follow, i.e. whether to continue to the body of the if statement or jump to the else block. It then starts executing whichever branch if guesses. If it guesses correctly, then the pipeline stays full. If it guesses incorrectly, the pipeline is flushed and none of the results of the instructions after the branch missprediction are committed. The processor resets itself to the branch and continues down the right track.

The branch predictor in the A5 gets about a 95% hit rate, so on average you have to flush the pipeline every 20 branches, which isn't too bad in terms of overhead. Superscalar makes no difference to the need for branch predictors. A superscalar chip is one that can issue more than one instruction per cycle. That means that independent instructions can be run side by side. This is quite nice on ARM chips, where a lot of instructions are predicated, as you can run both versions in parallel and only commit the one that was meant to be taken, but it's completely independent of the branch predictor.

It doesn't sound like it is necessarily slower, either, since you can get the same functions as the A8.

Nonsense. By that logic Atom is as fast as a Core 2 because you have the same instruction set on both. The A5 and A8/9, due to massive implementation differences, will execute different numbers of instructions per clock and not run at the same clock speed. The A5 will execute far fewer and runs at a lower frequency.

Wifi + LCD, not the CPU

[Gothmolly]

Its the Wifi/WWAN chips, and LCD screen which suck up the power, not the CPU. ARM is cool and all (pun intended) but if you make an ARM based Dell Mini 9, you're not going to end up with uber battery life, when you're on Wifi and running the screen bright.

Re:MS

[0123456]

Microsoft can really change things around if they decided to port Win7 to ARM, instead of offering only Windows CE.

But considering monopolies, I wouldn't expect that any time soon.

People generally use Windows on PCs because they have x86 Windows software they need to run.

How many people have a stack of ARM software to run on ARM Windows? If you're going to need new software anyway, why would anyone in their right mind pick Windows to run it on?

More info at Arstechnica

[IYagami]

http://arstechnica.com/gadgets/news/2009/10/arm-fills-out-cpu-lineup-with-cortex-a5.ars

http://www.brightsideofnews.com/news/2009/10/21/arm-announces-cortex-a5-for-the-next-15-billion-cellphones-and-mids.aspx

Re:First the Beatles; Now the ARM?

[SimonTheSoundMan]

Acorn Computers tried in the 80's and 90's. The ARM processors were faster than their x86 rivals, and OS was years ahead of the likes of Windows and Mac OS. As you say, some monopolistic software company would never allow ARM to take off. Lucky ARM is now the most common architecture on the market.

It's sad x86 is still here, the platform should have been done away with years ago.

Re:MS

[TheRaven64]

I've said this before. Aside from games, very little legacy software is CPU-bound. A modern emulator can get somewhere between 50-80% of the host native speed on emulated software, and not all of the code that is running will be emulated. Take a look at a typical Windows application. Most spend at least 50% of their CPU time in system library code. A half-decent emulator will just pass these calls to the native versions of the libraries, so for half of the CPU time you are running native code. A lot of recent Windows applications use some .NET code. This will be JIT compiled to ARM, so it's also native. The remaining code will be emulated, but the number of programs for which this will be too slow is very small.

Oh, and most people do not have a stack of x86 Windows software. They have one or two Windows programs that they depend on (or, at least, would not abandon without a lot of persuasion). You can bet that an ARM version of Windows would be accompanied by an ARM version of Office, and if MS really wanted to push it then they'd give a free download of the ARM binaries to people who owned the x86 version.

In terms of C programming environment, x86 and ARM are very similar. C does a terrible job at abstracting the differences between SPARC64 and x86 (for example), but it does a lot better at abstracting the differences between ARM and x86. Most software, unless it uses inline assembly or SSE / MMX intrinsics, is a straight recompile. The SSE and MMX intrinsics can be implemented in terms of NEON or slower scalar operations, so the code will compile, even if it doesn't get the same performance.

Re:Press Release

[Paladin128]

And it's full of misinformation:

1) The A5 is not meant to take on Atom. The A9 is.
2) The A5 is not architecturally identical to the A9. The A9 is an in-order, multi-issue core. The A5 is an out-of-order, single-issue core. The only thing similar is it has the Cortex A-series ISA.

What the A5 is is a CPU that completely obliterates the ARM11-derived cores, used in everything from NVIDIA Tegra to the Nintendo DS. It's an update of the ISA, and a more capable core, with better thermals. That's it. Whereas every low-end smartphone now has the same damn QualComm ARM11-based core, in a year, they'll all have the A5.