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SubjectRe: Qs: 1->many Pentium CPU upgrade (kernel 2.2.5)
Igor Markov wrote:
>
> Hello,
>
> I have a few questions regarding the behavior of 2.2.5 and above
> during a hardware upgrade. The answers that I would be most happy to
> hear are "upgrade your hardware and everything will work just fine",
> but I am not very optimistic (call it a hunch ;-). It seems important
> to know the answers before buying new hardware, but I could not find
> them in FAQs or other online docs. E.g., SMP is typically covered
> either from the developer's point of view, while I mainly care about
> not losing my system during upgrade and being able to run independent
> processes on difft processors (e.g., using make -j2) afterwards.
>
> If you believe my questions are not appriate for this list,
> I'd be happy to receive suggestions as to better places to post at.
> Pointers to relevant docs are also welcome.

There is a more specialized list:

linux-smp@vger.rutgers.edu

but this one is Ok too.

>
> Since I am not subscribed to this list,please
> cc: imarkov@cs.ucla.edu
> when replying
>
> ---------- end disclaimers ---------------------------------------------
> ---------- begin content ---------------------------------------------
>
> I am running an out-of-the box (no kernel rebuilds/upgrades)
> RedHat6.0 on a Pentium 150 w 96Mb RAM and a 3.2Gb HD.
>
> The upgrade is motivated by two factors
>
> o the latest gcc/g++2.95.1 (http://egcs.cygnus.com) can finally
> compile my C++ code and I am not anymore confined to SunPro CC
> or MSVC++

You must have very special C++ code... Be careful that gcc 2.95 is reported
to miscompile the kernel.

> o our lab has a number of spare Pentium II/350 processors donated
> from Intel and the multi-proc. motherboards do not look too much
> pricier than uni-proc. ones.
>
> I plan to buy a motherboard for 2 or 4 processors, a new case and new
> memory (I've been told that my curr. 96Mb chips may not work well with
> new boards). I am going to keep the peripherals.

You will probably get a BX motherboard with a 100 MHz bus. So you need
PC100 SDRAM memory. If you currently are using EDO or FPM chips those won't
do.

>
> The questions are
>
> 1. I expect the current [binary] kernel to recognize a new
> motherboard and at least one new processor immediately after
> the upgrade. Will that work if the board has 2 or 4 processors
> installed?

You will have to recompile the kernel with SMP enabled or install
the SMP kernel rpm (something like kernel-smp-2.2.5-15.i686.rpm)

>
> 2. One of the 2.2 kernel reviews on the Web alluded to
> the possibility to turn SMP on w/o recompiling the kernel...
> is this really possible or was that my misunderstanding ?

Only if we have one previously compiled for SMP (see above).


>
> 3. If I need to rebuild the kernel, I would also consider downloading
> a newer one before rebuilding. Since I do not have problems with 2.2.5
> running on one processor, I am curious if there are any advantages
> in getting a new kernel. I do seem to have one of those Ethernet
> cards that caused sudden death in combination w SMP, but I am not
> using it since I have no Ethernet connection.
>
Newer kernels usually mean fewer bugs and/or more features. If yours work
fine
and there are no new drivers/bug fixes that interest you in a more recent
kernel
there is no particular harm in sticking with the one you have.


> 4. Any comments on choosing 2-processor vs 4-processor motherboard?
> (Since I am going to use the processors for faster builds, it seems
> I should be able to use 4 processors w no problem).
>

Only Pentium Xeon supports 4 way SMP boards and even then this are hard to
find.
Intel only sells them as part of complete systems.

> thanks,
>
> Igor
> P.S. Please cc: your replies to imarkov@cs.ucla.edu



Rui Sousa

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