Digital Foundry: Microsoft gives more CPU power to Xbox One developers

ElTorro

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May 15, 2013
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#1
http://www.eurogamer.net/articles/d...es-more-cpu-power-to-xbox-one-developers-blog

Up until recently, both Xbox One and PlayStation 4 have reserved two entire CPU cores (out of eight available) in order to run the background operating system in parallel with games. Since October, Microsoft has allowed developers access to 50 to 80 per cent of a seventh processing core - which may partly explain why a small amount of multi-platform titles released during Q4 2014 may have possessed performance advantages over their PS4 counterparts in certain scenarios.

However, there's no such thing as a free lunch, and the additional CPU power comes with conditions and trades attached - however, there is the potential for many games to benefit. Firstly, developers need to give up custom, game-specific voice commands in order to access the seventh core at all, while Kinect's infra-red and depth functionality is also disabled. Secondly, the amount of CPU time available to developers varies at any given moment - system-related voice commands ("Xbox record that", "Xbox go to friends") automatically see CPU usage for the seventh core rise to 50 per cent. At the moment, the operating system does not inform the developer how much CPU time is available, so scheduling tasks will be troublesome. This is quite important - voice commands during gameplay will be few and far between, meaning that 80 per cent of the core should be available most of the time. However, right now, developers won't know if and when that allocation will drop. It's a limitation recognised in the documentation, with Microsoft set to address that in a future SDK update.
It's an interesting theory, but the timing of the presentation (August 2014 - two months before the new feature was added to the SDK) suggests not. Speaking to a prominent developer, one potential explanation is that differences in code compiler efficiency might favour Microsoft's console right now. How the availability of a seventh processing core will affect game performance going forward remains to be seen. Certainly, the whole point of Ubisoft's presentation is that moving CPU tasks to GPU is the future, and in this respect, it is the PS4 that is in the driving seat. Based on the single example Ubisoft's presentation provides (and it's worth stressing that all of these numbers are derived from just one piece of code), PS4 is almost twice as fast.
 
Jan 31, 2008
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#10
Aren't those dsabled to mitigate chip fail rates or something? It's late(early) and I cant think of the terms, but wouldn't there be some 7th cores that are theoretically damaged because they were disabled for that very reason?
 
Jan 14, 2010
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Mar 26, 2013
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#17
which may partly explain why a small amount of multi-platform titles released during Q4 2014 may have possessed performance advantages over their PS4 counterparts in certain scenarios.
Except that this additional CPU power was only available to devs in November SDK, so I highly doubt November games would use these new yet unproven November SDK features.
 

ElTorro

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#18
Yeah 50 to 80% on one core explain multiples fps difference
The difference is not trivial either, though. 9% more clock speed on all cores, variable CPU time on a 7th core, and allegedly better compiler performance should add up enough to give it some significance. That's not huge, that's not even much, but it is above negligible.

The article doesn't even imply this at all, in fact, it implies the exact opposite.
Yeah, especially improvements in the OS reserve are to be expected on the PS4, especially since it is very likely doing less in the background than the XBO. The only thing that won't change is the clock speed.
 
Oct 21, 2012
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#19
I fully expect Sony to follow suit, it's not like there is a lot running in the background. AMD apus was a mistake.
Yup pretty much, 8 x86 week cores makes no sense whatsoever for Game development... There shouldn't be a need to keep up with 6-7 threads to handle game logic, just because your IPC performance is +10 years old.
 
Nov 14, 2013
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#20
I'd suggest that the system disable voice command as soon as the game launches from the dashboard. Having voice command just idling until the word 'Xbox' comes into play seems to be a waste of power. Forcing the developer to have to delicately balance their abilities with an unimportant aspect of the X1 seems like a slap in the face.
 
May 2, 2014
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#21
Yup pretty much, 8 x86 week cores makes no sense whatsoever for Game development... There shouldn't be a need to keep up with 6-7 threads to handle game logic, just because your IPC performance is +10 years old.
What would have been a good CPU that is cheap enough though?
I doubt they could've gone with a high end CPU money wise.
 
May 3, 2011
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#23
its unlikely an sdk update in october effected any titles that released this christmas unless the the game was updated to take advantage of these capeabilities in a post release patch.

It's good news though more control / performance is always better.
 
Jun 7, 2004
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#24
Not concerned about performance verses PS4 but i am interested in MS continued effort to balance Xbox one for optimal results. Fascinating, thanks for posting this.
 
Mar 15, 2014
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#25
I can see the compiler optimisations making a big difference, but the extra CPU availability sounds problematic: devs can use more of the tin, but the OS might grab it back at any moment to process voice commands. You can use the extra power, but your code needs to run fine without it.
 

ElTorro

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May 15, 2013
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#26
Last I checked it's usually a good idea to read the article or at the very least the quotes in the OP so that a discussion about the information provided can be had.
Especially since nobody ever quotes the entire article. That would be unfair towards the author, and probably not even legal.
 
Aug 24, 2011
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#27
What would have been a good CPU that is cheap enough though?
I doubt they could've gone with a high end CPU money wise.
Not to mention that different seperate more ''high end'' processor would have also raised other costs of the console. They would have needed bigger case, more cooling etc. Going by sales and how especially Sony is probably already profiting from hw they made the right choice.
 

cyberheater

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Mar 10, 2005
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#29
I can see the compiler optimisations making a big difference, but the extra CPU availability sounds problematic: devs can use more of the tin, but the OS might grab it back at any moment to process voice commands. You can use the extra power, but your code needs to run fine without it.
A modern multi core scheduling game engine should have no problem with that.
 
Oct 21, 2014
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#34
I dont find the use of another core to gain of 4-5 fps stupid. I find very likely it to be the cause, in fact.

It can be like a 1.5+GHz overclock on specific scenarios.

Why is people laughting about that?
 
Oct 24, 2005
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#38
Wow so, Xbox One has 10% faster CPU and now an extra core that's another 12.5%.

So 22.5% more CPU power.

Now the performance advantages in GTA:V and AC:U makes sense.
 
Oct 6, 2010
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#41
I can't really see devs get anything realm meaningful from this boost until MS updates the tools so devs could see how much of the 7th core is available. Hopefully they'll get it locked to a certain percentage.
 
Jun 13, 2012
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#42
I can't really see devs get anything realm meaningful from this boost until MS updates the tools so devs could see how much of the 7th core is available. Hopefully they'll get it locked to a certain percentage.
Most devs develop to lcd. Right now, that means x1 gpu and ps4 cpu, worst of both worlds. First party stuff, tho...
 

cyberheater

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Mar 10, 2005
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#44
I can't really see devs get anything realm meaningful from this boost until MS updates the tools so devs could see how much of the 7th core is available. Hopefully they'll get it locked to a certain percentage.
There are probably call back functions available to programmers to determine that or thay could write there own.
 
Jul 26, 2013
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#47
Wow, I didn't realize this was already released. I was under the impression that these CPU gains were coming, not already here. Explains some of the AC Unity stuff I guess, but I wonder what this means for future games.
 
Apr 7, 2013
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Saskatoon, SK
#50
Not that they ever would, but it'd be interesting to see some of those early 3rd party games(Ghosts, BF4, AC4, MGS) remastered on this kind of "new" Xbox. Would the games be closer to PS4 performance or beating it in some cases?