Dropping i386 non-PAE as a supported kernel flavour in Precise Pangolin

Tim Gardner tim.gardner at canonical.com
Mon Nov 28 16:40:53 UTC 2011

On 11/09/2011 02:43 PM, Tim Gardner wrote:
> Per discussion at UDS the kernel team is proposing to drop the non-PAE
> i386 flavour. The upgrade path for non-PAE users will be the PAE kernel.
> Those CPUs that do not have i686 and PAE support will be orphaned. To
> the best of my knowledge, these include Intel CPUs prior to Pentium II,
> 400Mhz Pentium M, VIA C3, and Geode LX. As far as I know, there are no
> laptop or desktop class CPUs being produced that do not meet these
> minimum requirements.
> Before I do something that is difficult to revert, I would like to hear
> from the development community why we should continue to maintain a
> kernel flavour that is (in my opinion) getting increasingly low
> utilization. It is my feeling that an extremely high percentage of users
> of the non-PAE kernel have a CPU that is PAE capable.
> If there is sufficient community demand (and support), I would be
> willing to sponsor the first non-PAE kernel upload to Universe.
> https://wiki.ubuntu.com/KernelTeam/Specs/PreciseKernelConfigReview
> We'll be conducting a similar survey for powerpc.
> rtg
> P.S. For those of you that are totally confused by this email, PAE
> (Physical Address Extension) was an addition to 32 bit x86 CPUs that
> allowed them to address more then 4GB physical memory.
> http://en.wikipedia.org/wiki/Physical_Address_Extension

Thank you to everyone who responded to this thread.

To summarize, no compelling hard evidence has been presented to change 
my original decision. I am opposed to supporting non-PAE CPUs for 
another 5 years.

Colin King has developed power and performance profiling data that 
indicate the differences between PAE and non-PAE are negligible. I've 
also discussed this with OEM regarding possible future LTSP projects and 
have concluded it will have no detrimental impact.

Every flavour maintained by the kernel team has an incremental impact, 
especially when it comes to test builds and the full packaging cycle. 
Every flavour must also be tracked by meta packages. Every flavour has 
its unique class of bugs; non-pae has a ginormous and ugly NX emulation 
patch that has consumed substantial maintenance resources in the past, 
not to mention all of the bugs complaining about memory holes and the 
4Gb limit.

The kernel team has limited resources. Obviously I want to apply what 
resources we have to the problems that affect the most important 
platforms. Furthermore, I anticipate new ARM flavours in the coming 
months which will take up any slack afforded by the loss of non-PAE.

It is my recommendation that folks running PAE incapable CPUs stay on 
Lucid (10.04), a release for which they'll still receive more then 3 
years of official support.

If you feel passionately that I've made an incorrect decision, then I 
suggest contacting the Ubuntu technical board.


Tim Gardner tim.gardner at canonical.com

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