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Patch.DOC
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1990-01-26
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Patch2090 Version 1.0:
By: Khalid Aldoseri.
Patch2090 will fix the problems that the CBM 2090 and 2090A controllers
have when heavy DMA activity is present, i.e. when the display is hi-res,
and 4-bit planes (16 colors) while reading from Fast Filing System (FFS)
paritions. This problem is very evident with SCSI drives.
NOTE: Patch2090 will only work if you have autoconfig FAST memory
starting from $200000. (i.e. a standard mem expansion.) If you have both
'semi-fast' memory and normal fast memory, then the first command in your
startup-sequence _must_ be 'FastMemFirst' This can be found in the 1.3
release disks.
To use Patch2090 just run it:
run Patch2090
or runback Patch2090
There are several things you must make sure of first:
- You must add a line in your mountlist to every FFS parition with
the following: "MaxTransfer = 0x77abcdef". The number is critical,
make sure you have it correct.
- All FFS partitions must be mounted and accessed before Patch2090
is run.
- Patch2090 should be run as early as possible in the startup-sequence,
preferably right after all the FFS partitions have been accessed.
Once run, the program will keep checking as IO is done to the hard disk.
If the display meets the problem conditions (i.e. hires/16 colors) Patch2090
will automatically reduce the hd transfer rate in order to avoid the problem.
However, as soon as the display returns to normal, full hd transfer speed
will be restored.
Programs that are confirmed to have problems with DMA are DPaint and
ProPage and 16-color Workbench. My testing confirms that Patch2090 fixes
their problems.
Once you have run Patch2090, there is no way to remove it. You shouldn't
have to remove it anyway. :-) There is another version of Patch2090 that
has the facility to be removed from memory. I have not distributed this
due to the fact that if you don't know what you're doing, quitting Patch2090
will likely result in a colorful guru!
Note: Patch2090 can only be run once.
Please try this out with as many combinations as possible. Bug reports,
performance reports, suggestions, etc, etc. should be sent to my via easyplex.
Examples:
A Devs:Mountlist FFS entry:
FAST1:
Device = hddisk.device
FileSystem = l:FastFileSystem
Unit = 3
Flags = 0
Surfaces = 8
BlocksPerTrack = 33
Reserved = 2
Interleave = 0
LowCyl = 10 ; HighCyl = 775
GlobVec = 1
Mount = 1 <---- This makes 'Mount' access the partition
BufMemType = 1 as soon as it is mounted.
DosType = 0x444F5301
MaxTransfer = 0x77abcdef <---- Add this line to each FFS partition
#
Startup-Sequence:
FastMemFirst
Binddrivers
Mount FAST0:
Mount FAST1:
Mount FAST2:
runback c:Patch2090
etc.
I am not responsible for any 'complications' that might arise because
of this 'operation' to your Amiga. (grin)
If you have any problems with the installation of the program, please
email me on Compuserve.
This program is freely distributable as long as you don't modify either
the code or this doc file.
Lots of thanks to Larry Phillips for all his help with this.
Khalid Aldoseri.
CIS 75166,2531.