ia32 kernel on amd64 box?

ia32 kernel on amd64 box?

[jlnance]

Hello All,
    Does anyone know if an ia32 kernel (specifically the one that comes with
Red Hat 7.2) will work on an SMP AMD Opteron machine?
    I know someone will want to know why I would want to, so here is the
explanation.  I want to evaluate the opteron port of Linux at work.  Buying
the Opteron machine is less risky if I can fall back to 32 bit Linux
if the 64 bit port does not work well.  This is particularly true since
the 64 bit servers do not seem to cost much more than similar Pentium
machines.

Thanks,

Jim

Re: ia32 kernel on amd64 box?

[Bill Nottingham]

jlnance@unity.ncsu.edu (jlnance@unity.ncsu.edu) said: 
> Hello All,
>     Does anyone know if an ia32 kernel (specifically the one that comes with
> Red Hat 7.2) will work on an SMP AMD Opteron machine?

Red Hat 7.2 may or may not work, I'm not sure we've tried back that far.
Red Hat 8.0 or 9 should work fine.

Bill

Re: ia32 kernel on amd64 box?

[Jamie Lokier]

Bill Nottingham wrote:
> Red Hat 7.2 may or may not work, I'm not sure we've tried back that far.

Why - is there anything at all missing from the AMD64's x86
compatibility, prior to activating 64 bit mode?

Or is it just that it should work, but you haven't tested it?

-- Jamie

Re: ia32 kernel on amd64 box?

[Timothy Miller]

Jamie Lokier wrote:

>Bill Nottingham wrote:
>  
>
>>Red Hat 7.2 may or may not work, I'm not sure we've tried back that far.
>>    
>>
>
>Why - is there anything at all missing from the AMD64's x86
>compatibility, prior to activating 64 bit mode?
>
>Or is it just that it should work, but you haven't tested it?
>
>
>  
>
How about peripheral compatibility?

Re: ia32 kernel on amd64 box?

[Bill Nottingham]

Jamie Lokier (jamie@shareable.org) said: 
> > Red Hat 7.2 may or may not work, I'm not sure we've tried back that far.
> 
> Why - is there anything at all missing from the AMD64's x86
> compatibility, prior to activating 64 bit mode?
> 
> Or is it just that it should work, but you haven't tested it?

Nothing's wrong from the x86 compat standpoint, it's more
device support I'm unsure about (and that I haven't tested
it.)

Bill

Re: ia32 kernel on amd64 box?

[Andreas Jaeger]

jlnance@unity.ncsu.edu writes:

> Hello All,
>     Does anyone know if an ia32 kernel (specifically the one that comes with
> Red Hat 7.2) will work on an SMP AMD Opteron machine?

Any 32-bit x86 kernel should work on an AMD Opteron machine.  The only
question is whether all drivers are supported.  Red Hat 7.2 might not
have support for all the hardware that is in an AMD Opteron ystem.

>     I know someone will want to know why I would want to, so here is the
> explanation.  I want to evaluate the opteron port of Linux at work.  Buying
> the Opteron machine is less risky if I can fall back to 32 bit Linux
> if the 64 bit port does not work well.  This is particularly true since
> the 64 bit servers do not seem to cost much more than similar Pentium
> machines.

SuSE Linux 8.2/x86 works on AMD Opteron systems and I guess current
Red Hat distributions do work also,

Andreas
-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.inka.de
    http://www.suse.de/~aj

Re: ia32 kernel on amd64 box?

[Andi Kleen]

Jeffrey Baker <jwbaker@acm.org> writes:

> I was wondering the same thing about peripherals.  The
> README in aic79xx driver from adaptec states that the driver
> is supported on x86 only.  So I was wary to spec model 39320
> HBAs in x86-64 machines.  I'm sure Adaptec is using the term
> "support" in the most corporate sense possible, but what if
> it really does scribble the disk under SuSE 64-bit kernel?

The AIC 7xxx driver works fine. It should work on the same hardware as
79xx. 

The biggest AMD64 issue with drivers is normally IOMMU support, but
that only needs to concern you when you have more than 4GB of memory
and the hardware does not support 64bit Addresses. The Adaptec 
hardware supports 64bit addresses.

What's a problem is the "Adaptec RAID" - which uses the dpt_i2o driver.
That driver is not 64bit safe and doesn't work and is disabled.

-Andi

Re: ia32 kernel on amd64 box?

[Jeffrey Baker]

I was wondering the same thing about peripherals.  The
README in aic79xx driver from adaptec states that the driver
is supported on x86 only.  So I was wary to spec model 39320
HBAs in x86-64 machines.  I'm sure Adaptec is using the term
"support" in the most corporate sense possible, but what if
it really does scribble the disk under SuSE 64-bit kernel?

-jwb

Re: ia32 kernel on amd64 box?

[Andi Kleen]

Andreas Jaeger <aj@suse.de> writes:

> Any 32-bit x86 kernel should work on an AMD Opteron machine.  The only
> question is whether all drivers are supported.  Red Hat 7.2 might not
> have support for all the hardware that is in an AMD Opteron ystem.

Actually some things will not work with older kernels because the
Linux kernel does explicit CPUID model checks in a few places. But it
is relative obscure stuff and unlikely to be a problem in
practice.

-Andi