Ubuntu

Issue with i9-10900TE while activating PAE on linux kernel 5.15.x

Asked by Olivier Artigues

Hi,

I've to compile a linux 32b kernel 5.15.86 RT56 for running on 2 different computers with Intel CPUs : one with an i7-9700TE and 32Gb RAM, and the other one using an i9-10900TE with 64 Gb RAM.

I need to activate the support of 64Gb of RAM (CONFIG_HIGHMEM64G=y) + PAE (Physical Address Extension) Support (CONFIG_X86_PAE=y)

Once the linux kernel is compiled, it is working correctly on the i7-9700TE CPU computer. No issue there.

But impossible to start it on the i9-10900TE CPU computer : black screen at startup without any keyboard, nothing. It is saying that such a result occurs when the CPU is not PAE compatible...

I've checked on the Intel description of the Intel i9-10900TE where PAE compatibility is set.

If I disable the PAE (Physical Address Extension) Support (CONFIG_X86_PAE=n) and set support of 4Gb of RAM instead of 64Gb (CONFIG_HIGHMEM4G=y), then the i9-10900TE CPU computer is starting correctly using the compiled linux 32b kernel 5.15.86 RT56, but with limited RAM support which is not what I'm expected.

I've asked the same to Intel community, but they asked me to post my query on Ubuntu community.

Could you please tell me why it is not possible to enable 64Gb of RAM (CONFIG_HIGHMEM64G=y) + PAE (Physical Address Extension) Support (CONFIG_X86_PAE=y) on an i9-10900TE cpu ?

I can provide the full .config kernel compilation file for checking, even if I don't know how to do that here ?

Best regards

Olivier

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actionparsnip (andrew-woodhead666) said : 		#1

Why would you want to? Why do you want a 32bit kernel. 64bit CPUs have been around for a long long time.... Why bother with this ancient architecture?

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Olivier Artigues (oartigues) said : 		#2

Currently our solution is sold using this "old" 32 bits architecture. It is like it.
The question is not why using such an architecture, but why it is not working using it.

Regards

Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#3

If the application installs using a deb then it should simply work and the relevant stuff will be pulled in.

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Olivier Artigues (oartigues) said : 		#4

I know this kind of workaround that a 32bits deb package may work on a 64bits environment with the proper librairies.
But our customers are using the 32 bits OS and it is not acceptable to change it to 64 bits once installed due to commissioning already performed.

That's why I would like to understand why this 32 bits kernel is working with PAE + 64Gb ram support using an i7-9700TE, but not using an i9-10900TE.
Could you please help me to understand the reason ?

Regards,

Revision history for this message
Manfred Hampl (m-hampl) said : 		#5

I assume that this question can only be answered by kernel developers. https://kernel.org/category/contact-us.html indicates that https://superuser.com/ or https://serverfault.com/ may be addresses that are better than this one.

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Olivier Artigues (oartigues) said : 		#6

Ok, thanks I'm forwarding it to kernel.org.

Best regards

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