Re: Re: Instal failiures on a Macintosh LC475
On Tue, 20 Sep 2005, Michael Tomkins wrote:
> Stephen R Marenka wrote:
>
> Did you confirm that you don't have one of the problematic 68LC040s? I
> had to swap mine out before the system was stable for any length of
> time.
>
> And we have a winner. The LC 475 is doing a memory swap and recording
> the contents of a broken FPU/CPU to swap/ramdisk(the m68LC040) and when
> the data comes back its rubbish.
>
> You cannot run a stable Linux distro on any of the problem chips.
...under linux 2.2. Once 2.6 becomes stable, it will be possible, and some
updates will need to be made to the doco (below).
> What happened with my Quadra 605 (A rebadged LC475 or the other way
> around) was the same, it would boot, install and then some time later it
> would hang, in a seemingly random way. Get a m68040 CPU and everything
> works out fine.
>
> Relevant section of FAQ http://mac.linux-m68k.org/docs/faq.php
> Section IV: Hardware Requirements
> "5. What about the 680LC40's?
>
> This little chip can be quite a problem for the uninformed. If you have one of
> these chips, you may have a defective one that does not support any kind of
> FPU (floating-point) emulation. According to Motorola's official errata, any
> chip with a mask revision less than 2E71M has the bug. Specifically, revision
> 2E23G, used in the LC 475, has been confirmed to be buggy. Running Linux on
> one of these machines is possible, but probably not worth it.
If you have a 2.6 kernel with FPU emulation, and enough RAM, you can
disable swap. AFAICT, this should avoid the problem of page faults and FPU
instructions on those processors.
> You'll need to recompile all of your binaries not to use floating point
> (gcc's -m-soft-float option works nicely) and you'll need to hack your
> kernel to cause it not to try to save FPU register states while
> task-swapping. All in all, a hellish task and probably not worth it.
No kernel hacking is required to eliminate FPU code from the 2.6 kernel
any more. A userland built -msoft-float and a 2.6 kernel configured for no
FPU (neither emulated or real), should permit swap to work also.
-f
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