path: root/Documentation/m68k/README.buddha
diff options
authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/m68k/README.buddha
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'Documentation/m68k/README.buddha')
1 files changed, 210 insertions, 0 deletions
diff --git a/Documentation/m68k/README.buddha b/Documentation/m68k/README.buddha
new file mode 100644
index 00000000000..bf802ffc98a
--- /dev/null
+++ b/Documentation/m68k/README.buddha
@@ -0,0 +1,210 @@
+The Amiga Buddha and Catweasel IDE Driver (part of ide.c) was written by
+Geert Uytterhoeven based on the following specifications:
+Register map of the Buddha IDE controller and the
+Buddha-part of the Catweasel Zorro-II version
+The Autoconfiguration has been implemented just as Commodore
+described in their manuals, no tricks have been used (for
+example leaving some address lines out of the equations...).
+If you want to configure the board yourself (for example let
+a Linux kernel configure the card), look at the Commodore
+Docs. Reading the nibbles should give this information:
+Vendor number: 4626 ($1212)
+product number: 0 (42 for Catweasel Z-II)
+Serial number: 0
+Rom-vector: $1000
+The card should be a Z-II board, size 64K, not for freemem
+list, Rom-Vektor is valid, no second Autoconfig-board on the
+same card, no space preference, supports "Shutup_forever".
+Setting the base address should be done in two steps, just
+as the Amiga Kickstart does: The lower nibble of the 8-Bit
+address is written to $4a, then the whole Byte is written to
+$48, while it doesn't matter how often you're writing to $4a
+as long as $48 is not touched. After $48 has been written,
+the whole card disappears from $e8 and is mapped to the new
+address just written. Make shure $4a is written before $48,
+otherwise your chance is only 1:16 to find the board :-).
+The local memory-map is even active when mapped to $e8:
+$0-$7e Autokonfig-space, see Z-II docs.
+$80-$7fd reserved
+$7fe Speed-select Register: Read & Write
+ (description see further down)
+$800-$8ff IDE-Select 0 (Port 0, Register set 0)
+$900-$9ff IDE-Select 1 (Port 0, Register set 1)
+$a00-$aff IDE-Select 2 (Port 1, Register set 0)
+$b00-$bff IDE-Select 3 (Port 1, Register set 1)
+$c00-$cff IDE-Select 4 (Port 2, Register set 0,
+ Catweasel only!)
+$d00-$dff IDE-Select 5 (Port 3, Register set 1,
+ Catweasel only!)
+$e00-$eff local expansion port, on Catweasel Z-II the
+ Catweasel registers are also mapped here.
+ Never touch, use multidisk.device!
+$f00 read only, Byte-access: Bit 7 shows the
+ level of the IRQ-line of IDE port 0.
+$f01-$f3f mirror of $f00
+$f40 read only, Byte-access: Bit 7 shows the
+ level of the IRQ-line of IDE port 1.
+$f41-$f7f mirror of $f40
+$f80 read only, Byte-access: Bit 7 shows the
+ level of the IRQ-line of IDE port 2.
+ (Catweasel only!)
+$f81-$fbf mirror of $f80
+$fc0 write-only: Writing any value to this
+ register enables IRQs to be passed from the
+ IDE ports to the Zorro bus. This mechanism
+ has been implemented to be compatible with
+ harddisks that are either defective or have
+ a buggy firmware and pull the IRQ line up
+ while starting up. If interrupts would
+ always be passed to the bus, the computer
+ might not start up. Once enabled, this flag
+ can not be disabled again. The level of the
+ flag can not be determined by software
+ (what for? Write to me if it's necessary!).
+$fc1-$fff mirror of $fc0
+$1000-$ffff Buddha-Rom with offset $1000 in the rom
+ chip. The addresses $0 to $fff of the rom
+ chip cannot be read. Rom is Byte-wide and
+ mapped to even addresses.
+The IDE ports issue an INT2. You can read the level of the
+IRQ-lines of the IDE-ports by reading from the three (two
+for Buddha-only) registers $f00, $f40 and $f80. This way
+more than one I/O request can be handled and you can easily
+determine what driver has to serve the INT2. Buddha and
+Catweasel expansion boards can issue an INT6. A separate
+memory map is available for the I/O module and the sysop's
+I/O module.
+The IDE ports are fed by the address lines A2 to A4, just as
+the Amiga 1200 and Amiga 4000 IDE ports are. This way
+existing drivers can be easily ported to Buddha. A move.l
+polls two words out of the same address of IDE port since
+every word is mirrored once. movem is not possible, but
+it's not necessary either, because you can only speedup
+68000 systems with this technique. A 68020 system with
+fastmem is faster with move.l.
+If you're using the mirrored registers of the IDE-ports with
+A6=1, the Buddha doesn't care about the speed that you have
+selected in the speed register (see further down). With
+A6=1 (for example $840 for port 0, register set 0), a 780ns
+access is being made. These registers should be used for a
+command access to the harddisk/CD-Rom, since command
+accesses are Byte-wide and have to be made slower according
+to the ATA-X3T9 manual.
+Now for the speed-register: The register is byte-wide, and
+only the upper three bits are used (Bits 7 to 5). Bit 4
+must always be set to 1 to be compatible with later Buddha
+versions (if I'll ever update this one). I presume that
+I'll never use the lower four bits, but they have to be set
+to 1 by definition.
+ The values in this table have to be shifted 5 bits to the
+left and or'd with $1f (this sets the lower 5 bits).
+All the timings have in common: Select and IOR/IOW rise at
+the same time. IOR and IOW have a propagation delay of
+about 30ns to the clocks on the Zorro bus, that's why the
+values are no multiple of 71. One clock-cycle is 71ns long
+(exactly 70,5 at 14,18 Mhz on PAL systems).
+value 0 (Default after reset)
+497ns Select (7 clock cycles) , IOR/IOW after 172ns (2 clock cycles)
+(same timing as the Amiga 1200 does on it's IDE port without
+accelerator card)
+value 1
+639ns Select (9 clock cycles), IOR/IOW after 243ns (3 clock cycles)
+value 2
+781ns Select (11 clock cycles), IOR/IOW after 314ns (4 clock cycles)
+value 3
+355ns Select (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
+value 4
+355ns Select (5 clock cycles), IOR/IOW after 172ns (2 clock cycles)
+value 5
+355ns Select (5 clock cycles), IOR/IOW after 243ns (3 clock cycles)
+value 6
+1065ns Select (15 clock cycles), IOR/IOW after 314ns (4 clock cycles)
+value 7
+355ns Select, (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
+When accessing IDE registers with A6=1 (for example $84x),
+the timing will always be mode 0 8-bit compatible, no matter
+what you have selected in the speed register:
+781ns select, IOR/IOW after 4 clock cycles (=314ns) aktive.
+All the timings with a very short select-signal (the 355ns
+fast accesses) depend on the accelerator card used in the
+system: Sometimes two more clock cycles are inserted by the
+bus interface, making the whole access 497ns long. This
+doesn't affect the reliability of the controller nor the
+performance of the card, since this doesn't happen very
+All the timings are calculated and only confirmed by
+measurements that allowed me to count the clock cycles. If
+the system is clocked by an oscillator other than 28,37516
+Mhz (for example the NTSC-frequency 28,63636 Mhz), each
+clock cycle is shortened to a bit less than 70ns (not worth
+mentioning). You could think of a small performance boost
+by overclocking the system, but you would either need a
+multisync monitor, or a graphics card, and your internal
+diskdrive would go crazy, that's why you shouldn't tune your
+Amiga this way.
+Giving you the possibility to write software that is
+compatible with both the Buddha and the Catweasel Z-II, The
+Buddha acts just like a Catweasel Z-II with no device
+connected to the third IDE-port. The IRQ-register $f80
+always shows a "no IRQ here" on the Buddha, and accesses to
+the third IDE port are going into data's Nirwana on the
+ Jens Schönfeld february 19th, 1997
+ updated may 27th, 1997
+ eMail: