*-----------------------------------------------------------------------*
*		   Falcon MC68040 CPU ToolKit v5.00			* 
*-----------------------------------------------------------------------*


ECBACK40.TOS & DCBACK40.TOS
---------------------------


Description:
------------

Use the ECBACK40.TOS program to force all FastRAM to use the 68040
'copyback' cache facility. This will make anything which uses FastRAM
much faster than normal, but ONLY THE VERY CLEANEST OF CLEAN SOFTWARE
WILL WORK FOR MORE THAN A FEW SECONDS!

DBACK040.TOS disables copyback mode, and returns FastRAM to the normal
'write-through' mode set up by the driver.


Installation:
-------------

Run the programs from the Desktop. Don't try to put them in the auto
folder or things will start to go wrong.

Do not set the TT-ram flags in these 2 programs. That would be bad. :)


Important information:
----------------------

This feature is not the same as the copyback option in the driver itself,
as the driver only uses copyback mode on a very small area of ram which
is normally reserved for system use. These programs act on all available
FastRAM (claimed or otherwise) and should be used with great care.

When copyback is active, any programs which attempt to do the following:

* Alter the 68040 cache registers
* Alter the 68040 PMMU registers
* Use self-modifying code (relatively frequent with 68000 TSR's)

..will cause data held in the computer's memory to deteriorate quickly
over time and the machine will very probably crash. You will normally be
able to tell which programs are clean enough to use copyback mode simply
by the fact that they won't crash inside the first 30 seconds of use.

I do NOT advise using the copyback mode unless you are desperate for
speed - things like raytracing can benefit from the extra boost this can
supply. For reference, POVRay v3.00 (my port) and Apex Alpha both work
perfectly from FastRAM with copyback mode active, but a large number of
other programs will prove to be highly unreliable!

If the machine crashes due to a program conflicting with copyback mode
then you should reboot, because otherwise the machine can become
destabilized and crashing will continue until the machine cannot be used
any longer. This is caused by the cache containing stale data that is not
matched by that held in real memory, which is normally described as a
loss of cache coherency. This can't happen unless a program attempts one
of the points listed above (unless there are unpatched DMA devices in use
on your system).