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Q: What is "Nalle Puh"?
A: It's the Swedish name for Winnie the Pooh.
Q: Really?
A: Yup.
Q: But... Ehm. What does this program, "Nalle PUH", do?
A: It's a hack that intercepts some custom chip register accesses and
turns them into AHI function calls.
Q: How?
A: By using the MMU to mark the page at $dff000 as invalid.
Q: Invalid? Doesn't that mean you will get an exception each time the OS
or an application touches the registers?
A: Exactly.
Q: Isn't that kind of... slow?
A: You bet.
Q: How slow?
A: Unbearable.
Q: So the program is useless, then?
A: Not quite. It can be instructed to patch the OS and all applications that
read or write to the custom chip registers, so that next time the
instruction is executed, no exception will be generated.
Q: How?
A: A new chip register area is created at $80dff000. For the kickstart ROM,
all modules except audio.device will be patched to access this address
instead of $dff000. For applications, I simply guess when it's ok to
patch the instructions.
Q: Is that fool-proof?
A: Of course not. It's a hack. A proof of concept. Nothing more.
Q: Alright then. So what programs can be redirected?
A: I've tried the following programs, and they seem to work:
* audio.device
* Digibooster 1.7
* Musicline Editor 1.5
* Octamed Soundstudio 1.03c
* Protracker (version 2.3 and 4.0)
* THX Sound System 2.3d.
I've also tried the following, and they don't:
* Delitracker 2.32
* Newtracker
* PlaySID
(Note that Protracker disables multitasking and cannot be used with AHI
drivers that are not interrupt based.)
Previously, I wrote that Sid4Amiga also could be redirected, which is just
plain stupid, since Sid4Amiga already uses AHI. Duh! Sorry, Paul.
Q: Will you extend Nalle PUH so the all of those program work?
A: Unlikely.
Q: Pretty, pretty please!
A: No. The source code is available. Why don't you give it a shot yourself?
Q: Because <insert lame excuse here>.
A: Too bad.
Q: Suppose I do fix the program, is there anything else I should do?
A: You could certanly improve the instruction patching method. And it could
also be wise to set up a cachable Chip-RAM mirror so AHI won't have to
mix the samples from a non-cachable memory area.
Q: Hey! I found a memory leak: You don't close mmu.library! And you don't
clean up the MMU tables fully either.
A: I know. The custom chip register mirror must stay if applications were
patched. mmu.library must not be flushed from memory, or we loose the
mirror.
Version history:
0.1, 2001-04-23: * Initial release.
0.2, 2001-04-28: * Redirected logging to the listview in GUI mode.
* Minor GUI updates.
0.3, 2001-05-04 * Clears insr. caches when patching applications.
* Added a few more instr. patches (base relative).
This means that I had to move the register mirror
to $e00000. At least that area is unused on my A4000.
* The GUI does not touch the Paula registers on exit,
unless the user has pressed "Test" at least once.
* Final update! I've returned the sound card I
borrowed to write this hack. Thus, no more updates.
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Contents of driver/audio/NallePUH.lha
PERMISSION UID GID PACKED SIZE RATIO METHOD CRC STAMP NAME
---------- ----------- ------- ------- ------ ---------- ------------ ----------
[generic] 55972 55972 100.0% -lh0- e4e5 May 4 2001 NallePUH/MuLib/MuMin.lha
[generic] 2436 5488 44.4% -lh5- d41b Mar 27 2001 NallePUH/MuLib/MuMin.readme
[generic] 1813 6290 28.8% -lh5- 0625 Apr 14 2001 NallePUH/src/CompilerSpecific.h
[generic] 7097 19064 37.2% -lh5- 02ea Apr 22 2001 NallePUH/src/COPYING
[generic] 362 636 56.9% -lh5- 49a8 Apr 28 2001 NallePUH/src/Makefile
[generic] 5627 25744 21.9% -lh5- 4fdf May 4 2001 NallePUH/src/Nalle.c
[generic] 275 503 54.7% -lh5- 2ed6 May 4 2001 NallePUH/src/NallePUH.cd
[generic] 197 368 53.5% -lh5- b975 Apr 23 2001 NallePUH/src/NallePUH.h
[generic] 7989 24780 32.2% -lh5- 9303 Apr 28 2001 NallePUH/src/NallePUH.o
[generic] 938 3290 28.5% -lh5- a3d0 May 4 2001 NallePUH/src/NallePUH.res
[generic] 1131 4070 27.8% -lh5- e93d May 4 2001 NallePUH/src/NallePUHstr.s
[generic] 6989 6989 100.0% -lh0- cf9a Apr 23 2001 NallePUH/src/pooh11.gif
[generic] 32734 78004 42.0% -lh5- 10c5 Apr 23 2001 NallePUH/src/pooh11.o
[generic] 9736 50181 19.4% -lh5- 9c5c May 4 2001 NallePUH/src/PUH.c
[generic] 1413 3660 38.6% -lh5- e5a4 Apr 28 2001 NallePUH/src/PUH.h
[generic] 1699 3390 50.1% -lh5- 259f May 4 2001 NallePUH/src/README
[generic] 53967 125380 43.0% -lh5- 7113 May 4 2001 NallePUH/NallePUH
[generic] 1699 3390 50.1% -lh5- 259f May 4 2001 NallePUH/NallePUH.readme
---------- ----------- ------- ------- ------ ---------- ------------ ----------
Total 18 files 192074 417199 46.0% May 4 2001
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