Re: 2.1.101 patch to boot on toshiba Portege 660CDT laptop

H. Peter Anvin (hpa@transmeta.com)
26 May 1998 20:54:52 GMT

Followup to: <355B663E.A224D40@menuett.rhein-main.de>
By author: Jens Maurer <jmaurer@menuett.rhein-main.de>
In newsgroup: linux.dev.kernel
>
> In addition to that, Alan Cox correctly pointed out a few months
> ago that the patch is rather unclean. Therefore, I developed a
> nicer patch (attached below) which checks if we are on a 486 or
> better and if so, disables the caches around the A20 toggle.
> This is actually against 2.1.58, but seems to patch and compile
> cleanly for 2.1.101 as well. Note that I no longer have access
> to such a broken laptop and therefore need YOUR help to get it
> tested.
>

This is the wrong approach. ALL 486+ CPU's apply A20M before the L1
cache, so the only thing that would make this solve the problem is the
possibility that you're slowing the machine down.

You're much better off trying to implement an A20M delay verification
(put a counter in the low 64K and compare to the corresponding word in
the HMA; loop and increase the counter until they no longer match.)

-hpa

-- 
    PGP: 2047/2A960705 BA 03 D3 2C 14 A8 A8 BD  1E DF FE 69 EE 35 BD 74
    See http://www.zytor.com/~hpa/ for web page and full PGP public key
        I am Bahá'í -- ask me about it or see http://www.bahai.org/
   "To love another person is to see the face of God." -- Les Misérables


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu