Re: RESET vector

[Konrad Kokoszkiewicz <draco@mi.com.pl>]

I already got some signals that there's something wrong with the new
kernel and fast RAM.

> I can reproduce the following problem on a TT030 with both 4MB of
> ST and fast RAM.
> 
> Whenever I do a warm start under MiNT, my fast RAM disappears. I think
> this has to do with the so called bugfix for TOS 4.04, where ramvalid
> is zapped.
> 
> 1) What's the complete story behind this patch attempt?

The complete story is, that cold reboot to MiNT with VM manager enabled
used to produce two bombs shortly after the kernel displayed its welcome
message. There were no such effects on Sven's Karlsson TT030 (I wasn't
able to check it that time, because I didn't have a TT yet); no such
effect occurred on Falcons while warm booting either.

It took me some time to discover, that it is kmalloc() what bombs. It did
it legitimately trying to access the address $00000004 from user mode.

Next thing to discover was, that the TOS 4.04 always sets the ramvalid
magic value, even if the computer has no fast RAM (most Falcons don't).
The VM manager checked this value and assumed, that the fast RAM is
present and it begins at address $00000000. Hence the bombs.

First I added a small patch program to the distribution to get rid of all
that, but last time I added this code to the kernel. It works fine on my
Falcon, but apparently causes problems on other computers.

Well, since this code is mine, I am to blame :| 

> 2) And why does it screw up *my* system which has TOS 3.06?

I have no clue. My assumption was (perhaps it's wrong) that
core_malloc(-1,1) returns a zero if there's no fastram. If so (a zero is
returned), the ramvalid is invalidated (inside the init_mem()).

--
Konrad M.Kokoszkiewicz
|mail: draco@mi.com.pl                  | Atari Falcon030/TT030/65XE |
|http://www.orient.uw.edu.pl/~conradus/ |  *** FreeMiNT 1.14.7. ***  |

** Ea natura multitudinis est,
** aut servit humiliter, aut superbe dominatur (Liv. XXIV,25)
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