Path: utzoo!attcan!uunet!mcvax!unido!fauern!faui44!mlelstv
From: mlelstv@faui44.informatik.uni-erlangen.de (Michael van Elst )
Newsgroups: comp.sys.amiga
Subject: Re: KS clearing RAM (was Re: Infinite loop in a directory)
Keywords: ASDG board, Micron Boards.
Message-ID: <632@faui44.informatik.uni-erlangen.de>
Date: 9 Sep 88 13:03:35 GMT
References: <8818@swan.ulowell.edu> <964@esunix.UUCP> <144@antares.UUCP> <21346@tut.cis.ohio-state.edu>
Reply-To: mlelstv@faui44.UUCP (Michael van Elst (kdebugger))
Organization: CSD., University of Erlangen, W - Germany
Lines: 42

In article <21346@tut.cis.ohio-state.edu> stellrec@deneb.cis.ohio-state.edu (barry stellrecht) writes:
>
>I have also use ASDG's VD0: with a Micron chassis & 2Meg ram board, and it has
>survived changekick every time I did it.  (The Micron does have a write protect
>_jumper_ but that is only for a memory test program, and I've never used it)

Hello netpeople,

there is a simple explanation for this effect. A kickstart change does
always a coldstart of exec. Then chip-memory is cleared during the
memory test. Chip-memory is too partially overwritten at boot time because
you need some chip-memory buffer for the disk and some memory for the system
stack.
Ranger-Memory (addresses $c00000 up to $dbffff) are not cleared on coldstart
but I have not seen a memory expansion there for the A1000.

With other memory expansions you are always 'expansion-memory'
(addresses $200000 up to $9fffff). Simple expansion cards (added with
AddMem or a similar program) are not cleared at all except for the
AddMem program that might write into this memory to check if the
memory is available. I know of a version of AddMem that does this type
of destructive memory test.
Autoconfiguration cards may have a selftest program in an EPROM that
clears memory but I haven't seen anyone.

When VD0: is startet, that is after a MOUNT and the first access to it,
all free memory is searched for valid data and then allocated (I think
via AllocAbs call).

If something has overwritten part of the VD0-Disk you get a clean
one. So all is lost.

Conclusion, usually VD0: survives everything if it is located in
external memory and is started as the first command in your startup-
sequence.
VD0: in CHIP only survives warm starts (i.e. ExecBase is not corrupted).

				Michael van Elst

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