Re: [PLUG] AMD vs Intel, 486DX4/100

[Greg Lopp <lopp@earthlink.net>]

Bill Jonas wrote:

> On Wed, 3 May 2000, Bill Jonas wrote:
>
> >Anybody know if those particular chips are pinout- and
> >pin-layout-compatible?
>
> I guess I should clarify.  I recently acquired an AMD 486DX4/100.  I've
> tried to get Linux going on it, to no avail.  The Debian rescue disk, a
> simple boot disk and a LILO boot disk (both created with Slack7), and
> even booting a DOS floppy and using LOADLIN.EXE all result in the same
> error.  (Recently, after checking out some info @ seagate.com and
> changing a BIOS setting, a hard drive boot will give this same error.)
> Right after the BogoMIPS check and the memory check, when the kernel
> displays, "Checking if this processor honours the WP bit when in
> supervisor mode... OK.", I get a kernel oops and a stack dump, led off
> by the error message, "Unable to handle kernel paging request at virtual
> address $ADDRESS".  The oops is then followed by
>
> Kernel panic: Attempted to kill the idle task!
> In swapper task - not syncing
>
> On the advice of a co-worker, I suspected that it might be the CPU.
> (The message is the same each time, tho' I haven't bothered to check and
> see if the registers are different.)  I checked out the Hardware-HOWTO
> (http://www.linuxdoc.org/HOWTO/Hardware-HOWTO-4.html), and it says, "A
> few very early AMD 486DX's may hang in some special situations. All
> current chips should be okay and getting a chip swap for old CPU's
> should not be a problem."
>

Just asked one of our HW guys about pin compatability - we happen to use
AMD 486 chips here but have documentation for both around.  The two chips
are pin compatible, but motherboards present an issue.....both chips run on
3.3V, but a few of the pins on an Intel chip still require 5V (for I/O bus
access?).  The AMD chip accomplishes these same duties, but by using 3.3V.
Those 5V pins in the AMD chip do not go anywhere.  So if your mboard was
designed for Intel, it should also work with the AMD.  If your mboard was
designed for AMD, knowing that the 5V isn't necessary, it might not provide
it - causing Intel chips to fail.  A long answer to a simple question, but
yes, pin compatible they are.

Is this a fresh system or is there an old chip/configuration that you can
revert to?


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