Re: copy lfs build to older CPU

On 9/22/25 11:55 AM, Rainer Fiebig ([email protected] via lfs-support 
Mailing List) wrote:
> Am 22.09.25 um 16:37 schrieb Thomas Seeling ([email protected] via
> lfs-support Mailing List):
>> Hello dear list,
>>
>> I experimented (again) with moving a completed build of 12.4 64 bit to
>> an older machine.
>> My build machine has an i7-6700, and I unpacked this to an older i5-3350
>> after it successfully finished.
>> At first glance everything seemed to look fine until I tried to compile
>> ethtool (to gain WOL capability).
>> The `configure`  script went through but while compiling the source I
>> got an "illegal instruction" abort from gcc.
>> That was a bit surprising. I compiled the `gmp`  package as recommended
>> with ` --host=none-linux-gnu`.
> Also thought of libffi?
>
> Rainer

libffi is also a very good one!

Another one I want to bring up is OpenJDK. If you are using the JDK 
binaries that we provide, you should be okay. If you built it from 
source though, you'll need to recompile it on the older system, because 
OpenJDK also tends to build in support for CPU features automatically.

I work around this for BLFS by using a Qemu VM with CoreDuo set for 
i686, and Athlon64 set for x86_64 systems. Qemu hides those extra CPU 
instructions.

- Doug

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