Re: [gentoo-user] swapping processor problem

[Michael Mol <mikemol@gmail.com>]

On Tue, Nov 15, 2011 at 2:33 AM, Raffaele BELARDI
<raffaele.belardi@st.com> wrote:
> I have two gentoo boxes, X has an ASUS M2NPV-VM with AMD64 3500+ CPU, Y
> has a AMD64 X2 5600+ CPU. Since I need more juice on X I thought I could
> swap CPUs.
>
> After updating X's BIOS the system with the 'new' CPU boots up to the
> MythTv screen with no error but does not respond to the USB keyboard nor
> to the remote control keypresses. More precisely:
>
> - keyboard is fine at grub boot, I can select up and down or edit the
> entries
> - keyboard is no longer responsive at the init scripts start (when you
> can press 'I' to select services)
>
> My first thought was that X (and Y) WERE compiled with '-march=native'
> GCC flag and maybe the 5600+ does not execute properly the 3500+ code.
> But a quick search on wikipedia shows that 5600+ has a superset of the
> 3500+ so I should have problems putting the 3500+ in the Y box, not
> vice-versa.
>
> Any suggestions?

Play with your BIOS settings. Look for things like legacy USB support.
Also, double-check that all the relevant USB drivers (UHCI, EHCI,
XHCI, HID, etc) are either built-into the kernel, or are loaded as
modules. Consider rebuilding your kernel.

Just because one processor has a superset of the instructions of the
other doesn't mean there may not be other compatibilities. Some time
back, a thread on here discussed how to find out what -march=native
becomes, in terms of -march and a bunch of other parameters. I've
noticed parameters like cache line sizes and cache sizes, among a
couple others. I imagine a bungling of, e.g., cache line sizes could
break code that has heavy dependency on data locality and/or memory
models; it might have broken your USB drivers, for example.

But, really, I think BIOS settings and driver presence are the more
likely culprit.

-- 
:wq