Tuesday, September 6th 2016

SMT and Power Management Behind "Kaby Lake" and "ZEN" Windows 10 Restrictions

Microsoft recently sparked a stir when it was reported that the company will support upcoming CPU architectures by Intel and AMD only on Windows 10, with the keyword being "support" and not "compatibility." This means that Microsoft will offer customer-support and likely serve updates to Intel "Kaby Lake" and AMD "ZEN" machines only running Windows 10 (and its enterprise variant Windows Server 2016, based on the NT 10 kernel), and not older versions of Windows. The processors themselves are compatible with any x86 operating system, Windows or *nix, 32-bit or 64-bit. HotHardware dug out the likely causes of this decision.

Apparently, new power-management and SMT features are behind the decision. With its "Kaby Lake" microarchitecture, Intel is introducing a new power-management feature called Speed Shift Technology. This lets the processor adjust its clock-speed to match processing loads at response time of 15 ms. This likely requires OS-level hooks, so the on-die power-management components can poll for processing loads and accordingly raise or lower clock-speeds 66.66 times each second, at no CPU cost. In its ZEN microarchitecture reveal, AMD too spoke about fine-grained, multi-domain clock-gating (≠ power-gating) on its "ZEN" based processors, such as "Summit Ridge."
AMD "ZEN" processors introduce simultaneous multi-threading, a feature that exposes each physical core as two logical CPUs to the OS, for better utilization of on-die resources. Intel's implementation of SMT is the HyperThreading Technology (HTT), and has been around for over a decade. AMD's SMT implementation isn't identical to that of HyperThreading, with the two threads on a CPU competing for resources in a method unique to AMD. This can't work without the OS kernel and scheduler being aware of the method. You'll remember that Microsoft had to update the kernel and scheduler of Windows 7 in a similar way, to optimize it for "Bulldozer."

These, HotHardware argues, could be the likely reasons why Microsoft is limiting support for the new CPU microarchitectures to Windows 10.
Source: HotHardware
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57 Comments on SMT and Power Management Behind "Kaby Lake" and "ZEN" Windows 10 Restrictions

#1
Naito
People will still kick and scream over this.
Posted on Reply
#2
Frick
Fishfaced Nincompoop
So it'll work with older versions, but with slightly worse power management?
Posted on Reply
#3
Chaitanya
Frick
So it'll work with older versions, but with slightly worse power management?
Yeah probably, also device manufacturers: Intel and AMD will simply stop providing drivers for older version of windows.
Posted on Reply
#4
Xajel
Yeah, I still remember when Intel first introduced HyperThreading performance was not that great, and some apps actually suffered from lower performance as both the OS and Applications needs to be designed to benefit from it...

As Most Apps are optimised already for SMT ( thanks to Intel ), it's only a matter of OS optimise now for the new architecture which I suppose is different than Intel implementation of the original SMT, maybe few changes for applications also to benefit more from AMD's architecture and maybe also using AMD's new instructions ( which BTW I don't know what the use of these new ones )
Posted on Reply
#5
RejZoR
Wait, they are mentioning Speed Shift for i5 6500. While being slightly worse with it than with i5 7500, there seems to be some support. Does this mean older CPU's will also support Speed Shift to some degree? Wondering as a 5820K owner...
Posted on Reply
#6
bogami
If that would only resolved a problem .. I solved this by constant 4.8 Gh (i73770K normal 1.6Gh in game) operating frequency. no response and not to fall during the game not to mention survival in games FPS ...
Because I do not play on batteries and consumption is not so crazy , such as on 4. GPU does not bother and each generation got consumption improved.
Posted on Reply
#7
RejZoR
Actually it's the deeper C states (like C6) that cause this massive delay. SpeedStep by itself isn't as problematic. If you limit it to going down to C1 only, you'll still be saving power while eliminating most of the delay. C2 or C3 are still an option, but they'll already cause some delay.
Posted on Reply
#8
laszlo
step by step:
-shall i understand that win10 already could support new cpu arch?-i think no as when launched(July 2015 but surfaced Oct 2014 as beta test) amd didn't had the zen...
-this mean M$ will issue an OS update for this SMT?- yes
-could they make this update for older OS? -yes
-will they do?- no

why? - is another way to force implementation of win10....

Posted on Reply
#10
RejZoR
Ok, so 5820K doesn't have one at all.
Posted on Reply
#11
Frick
Fishfaced Nincompoop
laszlo
step by step:
-shall i understand that win10 already could support new cpu arch?-i think no as when launched(July 2015 but surfaced Oct 2014 as beta test) amd didn't had the zen...
-this mean M$ will issue an OS update for this SMT?- yes
-could they make this update for older OS? -yes
-will they do?- no

why? - is another way to force implementation of win10....


It's correct, but you can make the same argument about everything.
Posted on Reply
#12
Ferrum Master
I wonder where is the cry. New mobo means new legal OS is needed. Case closed.

Older ones are fine with that they have. Whatever it may be. Use linux and live.

Those are good ideas and are helping with progress. There is no reason to support old code for M$. Take it or leave it.
Posted on Reply
#13
bug
Ferrum Master
I wonder where is the cry. New mobo means new legal OS is needed. Case closed.
Not new OS, just new drivers. However, Windows 7's support ended in 2015 and Windows 8 and 8.1 were never that popular. Add to that the fact that 10 comes with an updated driver model and it becomes pretty clear why backporting isn't worthwhile.
On the other hand, it's not exactly a joy giving up an OS you're comfortable with, just to be able to use that new CPU. Imagine what this does to companies having hundreds of stations. They get the new OS for free, but still have to do some retraining.
Posted on Reply
#14
laszlo
bug
Not new OS, just new drivers. However, Windows 7's support ended in 2015 and Windows 8 and 8.1 were never that popular. Add to that the fact that 10 comes with an updated driver model and it becomes pretty clear why backporting isn't worthwhile.
On the other hand, it's not exactly a joy giving up an OS you're comfortable with, just to be able to use that new CPU. Imagine what this does to companies having hundreds of stations. They get the new OS for free, but still have to do some retraining.
win7 support end 2020....

Posted on Reply
#15
Melvis
Soooooo do a update Microsoft? not that hard :slap:

Or just turn off HTT/SMT?
Posted on Reply
#16
Frick
Fishfaced Nincompoop
Melvis
Soooooo do a update Microsoft? not that hard :slap:

Or just turn off HTT/SMT?
Defintely not an option these days.
Posted on Reply
#17
Melvis
Frick
Defintely not an option these days.
Always an option these days, in this time 2016 it should be a walk in a park its only Microsoft been lazy like all developers are theses days, sad really.
Posted on Reply
#18
Ferrum Master
It is not a driver/module. It needs baked in kernel support to use that kind of feature.
Posted on Reply
#19
bug
laszlo
win7 support end 2020....
Mainstream support has ended in 2015. That means no more enhancements, which is essentially what we're discussing here.
Edit: I'm not even sure you can get extended support (i.e. security patches) as a home user.
Posted on Reply
#20
Ubersonic
bug
Not new OS, just new drivers. However, Windows 7's support ended in 2015 and Windows 8 and 8.1 were never that popular.
laszlo
win7 support end 2020....
Extended support (security patches) ends in 2020, mainstream support ended in 2015.
Posted on Reply
#21
Vayra86
In other words, a lot of noise about nothing.
Posted on Reply
#22
laszlo
bug
Mainstream support has ended in 2015. That means no more enhancements, which is essentially what we're discussing here.
officially last oem pc's sale with win7&8 will end on :

"End of sales
End of sales refers to the date when a particular version of Windows is no longer shipped to retailers or Original Equipment Manufacturers (OEMs). Examples of OEMS are Dell and Toshiba—PC manufacturers who often preinstall Windows software.

This table gives end of sales dates for specific Windows operating systems.

Client operating systems and updates Date of general availability Retail software end of sales* End of sales for PCs with Windows preinstalled
Windows XP December 31, 2001 June 30, 2008 October 22, 2010
Windows Vista January 30, 2007 October 22, 2010 October 22, 2011
Windows 7 Home Basic, Home Premium, Ultimate October 22, 2009 October 31, 2013 October 31, 2014
Windows 7 Professional October 22, 2009 October 31, 2013 October 31, 2016
Windows 8 October 26, 2012 October 31, 2014 June 30, 2016
Windows 8.1 October 18, 2013 September 1, 2015 October 31, 2016"


extended support must provide all enhancements for specific sold hardware ;for sure these hardware won't have new gen cpu; point is you can't say one OS is obsolete once you still sell it....
Posted on Reply
#23
_Flare
So ONE big thing of the "Bulldozer-Fail" was obviously that too much of the CPU-Management was NOT IN HARDWARE, not only that, it needed the Software of other Companies: Microsoft etc.

To not rely on the Hardware-Solutions of your own engineers, OMG.

AMD i hope you did not make the same mistake twice !!!
Posted on Reply
#24
Frick
Fishfaced Nincompoop
bug
Edit: I'm not even sure you can get extended support (i.e. security patches) as a home user.
They do.
Posted on Reply
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