Preamble
I bought an used powermac, I was ever interested to this architecture: both the OpenFirmware and the powerpc processor fascinating me.
The machine was an old dual PowerPc @ 1GHz, equipped with 512MB of ram. The model was the one called PowerMac MDD (Mirrored Drive Doors).
Because it was an old and used machine, the machine had some problems:
- after few minutes, the system shut-down unconditionally, both under Mac OS X and Linux. I solved replacing the CPU-Board. I suspected that a temperature sensor drifted.
- time to time I noticed that some application under OS X crashed; some packages under linux were currupted. I solved replacing the memory.
Upgrading Mac OS X
When I tried to upgrade Mac OS X from 10.3 to 10.4, I had to use an USB stick (even the dvd reader didn't worked well) : first I copied the DVD image to the USB stick, then I faced the problem on HOW boot the machine from USB.
On a pc (I.E. a x86 one), it would be sufficient to select from the boot menu the USB stick as source. But in this kind of Macintosh, the things are different .... and more interesting !
OpenFirmware
Instead of the BIOS, these machine have "OpenFirmware". From an user point of view, OpenFirmware seems less capable of a BIOS. But OpenFirmware has its points of forces: for example it is an environment fully programmable, and it is also capable to access file inside a filesystem.
In this post I will introduce some OpenFirmware concepts, but definitely it has not to be considerable a course on OpenFirmware.
Access OpenFirmware
To access the OpenFirmware interface, you have to press 4 keys: CMD + OPTION + O + F. To access the BIOS interface usually it is needed to press one key (typically DEL !).
But there is another more interesting way to access OpenFirmware: via telnet ! This fact is enough to consider OpenFirmware a lot better than a classic BIOS !
To allow the telnet access to the OpenFirmware console, once you pressed the CMD-OPTIONS-O-F keys, you have to do the following commands:
0 > dev /packages/telnet ok
0 > " enet:telnet,192.168.10.47" io
0 > and ok). Pay attention to the space after " (double quote).Now to access OpenFirmware it is sufficient doing a telnet to the ip 192.168.10.47.
Devices tree
Usually on the OpenFirmware system, the hardware configuration are exported via an hierarchical structure which resemble a filesystem. This kind of structure is called device tree.
To see the device tree, you have to use the ls and dev commands. ls is like the ls unix command (or dir "dos" command); instead dev is like the cd command.
0 > dev / ok
0 > ls
ff87f638: /cpus
ff87f8e8: /PowerPC,G4@0
ff87fd10: /l2-cache
ff87ff48: /l2-cache
ff880ba8: /PowerPC,G4@1
ff880fd0: /l2-cache
ff881208: /l2-cache
ff881518: /chosen
ff881730: /memory@0
ff8819d0: /openprom
ff881b78: /client-services
ff882e60: /rom@ff800000
ff883060: /boot-rom@fff00000
ff883290: /macos
ff883398: /options
ff8834a0: /aliases
ff8854a8: /packages
ff885588: /deblocker
ff885f20: /disk-label
ff8869e8: /obp-tftp
ff8902c8: /telnet
ff890bc8: /mac-parts
ff892478: /mac-files
ff895430: /hfs-plus-files
ff89a4b0: /fat-files
ff89c2a8: /iso-9660-files
ff89d108: /bootinfo-loader
ff89ed78: /xcoff-loader
ff89f810: /pe-loader
ff8a0260: /elf-loader
ff8a1908: /usb-hid-class
ff8a4498: /usb-ms-class
ff8a70e8: /usb-audio-class
ff914c60: /sbp2-disk
ff917820: /ata-disk
ff919d60: /atapi-disk
ff91bef0: /bootpath-search
ff922870: /terminal-emulator
ff922980: /firewire-disk-mode
ff9383b0: /pseudo-hid
ff9384b0: /keyboard
ff938ba8: /mouse
ff939140: /eject-key
ff939610: /pseudo-sound
ff939940: /multiboot
ff94d758: /diagnostics
ff94d838: /nvram@fff04000
ff94e488: /uni-n@f8000000
ff94e960: /i2c@f8001000
ff94f478: /fan@58
ff9502f8: /i2c-hwclock@ca
ff950ae0: /temp-monitor@92
ff9511c8: /cereal
ff9518f8: /pci@f0000000
ff99cde0: /uni-north-agp@b
ff99d0f0: /ATY,PheonixParent@10
ff9b9048: /ATY,Pheonix_A
ff9baa50: /ATY,Pheonix_B
ff952b58: /pci@f2000000
ff9555e8: /mac-io@17
ff95c0c8: /interrupt-controller@40000
ff95c318: /gpio@50
ff95c548: /extint-gpio1@9
ff95c838: /programmer-switch@11
ff95cae0: /gpio5@6f
ff95cd00: /extint-gpio15@67
ff95cf88: /gpio6@70
ff95d1a8: /extint-gpio16@68
ff95d498: /extint-gpio14@66
ff95d720: /gpio12@76
ff95d938: /gpio11@75
ff95db50: /escc-legacy@12000
ff95ddc0: /ch-a@12004
ff95dfc0: /ch-b@12000
ff95e1c0: /escc@13000
ff95e448: /ch-a@13020
ff95ee70: /ch-b@13000
ff95f808: /i2s@10000
ff95fa38: /i2s-a@10000
ff95fd68: /sound
ff960600: /timer@15000
ff9607f8: /via-pmu@16000
ff963ec0: /pmu-i2c
ff964ce0: /i2c-hwclock@1d4
ff965590: /i2c-hwclock@1c8
ff965e10: /rtc
ff966508: /power-mgt
ff9bea18: /usb-power-mgt
ff966818: /i2c@18000
ff9672d0: /cereal
ff967a00: /deq
ff967b40: /ata-4@1f000
ff96a880: /disk
ff96b0c0: /ata-3@20000
ff96de00: /disk
ff97a580: /usb@18
ff9bc960: /hub@1
ff9bcb68: /mouse@1
ff9bce88: /device@3
ff9bd000: /keyboard@0
ff9bd390: /interface@1
ff982208: /usb@19
ff9bc630: /disk@1
ff953dd8: /pci@f4000000
ff989fd0: /ata-6@d
ff98d1b8: /disk
ff98d7f0: /firewire@e
ff9979f8: /ethernet@f
ff9beee0: /ethernet-phy
ff955038: /vsp@f9000000
ff955328: /veo@f9080000
ff955488: /veo@f9180000
ok
ff895430: /hfs-plus-files
ff89a4b0: /fat-files
ff89c2a8: /iso-9660-files
- HFS+
- FAT filesystem
- ISO-9660 (the one used in the cdrom)
Another interesting command is devalias, which lists some devices and their alias:
0 > devalias
pci0 /pci@f0000000
agp /pci@f0000000
pci1 /pci@f2000000
pci2 /pci@f4000000
ui2c /uni-n/i2c
ui2c-serial /uni-n/i2c/cereal
keyboard /pseudo-hid/keyboard
mouse /pseudo-hid/mouse
sound /pseudo-sound
eject-key /pseudo-hid/eject-key
nvram /nvram
enet /pci@f4000000/ethernet
fw /pci@f4000000/firewire
pci /pci@f2000000
usb0 /pci@f2000000/usb@18
usb1 /pci@f2000000/usb@19
mac-io /pci@f2000000/mac-io@17
mpic /pci@f2000000/mac-io@17/interrupt-controller
hd /pci@f4000000/ata-6@d/disk@0
cd /pci@f2000000/mac-io@17/ata-3@20000/disk@0
ide0 /pci@f2000000/mac-io@17/ata-3@20000/disk@0
ide1 /pci@f2000000/mac-io@17/ata-3@20000/disk@1
ultra0 /pci@f4000000/ata-6@d/disk@0
ultra1 /pci@f4000000/ata-6@d/disk@1
scca /pci@f2000000/mac-io@17/escc/ch-a
sccb /pci@f2000000/mac-io@17/escc/ch-b
ki2c /pci@f2000000/mac-io@17/i2c
ki2c-serial /pci@f2000000/mac-io@17/i2c/cereal
via-pmu /pci@f2000000/mac-io@17/via-pmu
rtc /pci@f2000000/mac-io@17/via-pmu/rtc
pi2c /pci@f2000000/mac-io@17/via-pmu/pmu-i2c
wireless /pci@f2000000/mac-io@17/@30000
ultra2 /pci@f2000000/mac-io@17/ata-4@1f000/disk@0
ultra3 /pci@f2000000/mac-io@17/ata-4@1f000/disk@1
cd1 /pci@f2000000/mac-io@17/ata-3@20000/disk@1
fan /uni-n/i2c/fan
veo0 /vsp@f9000000/veo@f9080000
veo1 /vsp@f9000000/veo@f9180000
last-boot /pci@f4000000/ethernet@f
screen /pci@f0000000/ATY,PheonixParent@10/ATY,Pheonix_A
ok
Give a more deeper look to the usb interface. From the device-tree list above, we know that under usb0 (/pci...usb@18) there is the apple mouse and keyboard. Instead under usb1 (/pci...usb@19) there is a disk.
To access a disk the full path is like:
/pci@f2000000/usb@19/disk@1/pci@f4000000/ata-6@d/disk@0 considering an ata disk)Adding ":nn" at the end of these "path", we identify a partition; as example the dir command will show the content of a filesystem inside the 2nd partition:
0 > dir /pci@f2000000/usb@19/disk@1:2,\
Size/ GMT File/Dir
bytes date time TYPE CRTR Name
82 3/21/ 5 4:25:52 ._Install%20Mac%20OS%20X
12292 10/10/ 5 22: 4:45 .DS_Store
8/ 4/14 17:53:21 .Spotlight-V100
8/ 4/14 18:49:47 .Trashes
3/21/ 5 0: 1:29 .vol
3/28/ 5 5:26:30 Applications
3/28/ 5 6:42:12 bin
3/23/ 5 2:36:40 dev
11 3/28/ 5 6:23:29 slnk rhap etc
3/28/ 5 4:21:28 Install%20Mac%20OS%20X
3/18/ 5 21: 4:34 Japanese%20-%20%u65e5%u672c%u8a9e
3/28/ 5 6:32:40 Library
11 3/28/ 5 6:23:29 slnk rhap mach
4313028 3/26/ 5 22:15:41 mach_kernel
3/26/ 5 1: 0: 2 Optional%20Installs.mpkg
3/28/ 5 6:23:29 private
3/21/ 5 3: 7:27 Read%20Before%20You%20Install.app
3/28/ 5 6:41:12 sbin
3/28/ 5 5:26: 8 System
11 3/28/ 5 6:23:31 slnk rhap tmp
3/28/ 5 5:30:43 usr
11 3/28/ 5 6:23:32 slnk rhap var
3/21/ 5 0: 1:29 Volumes
3/21/ 5 3: 7:27 Welcome%20to%20Tiger.app
3/28/ 5 5:19:56 HFS+%20Private%20Data
ok
To look inside a directory:
0 >dir /pci@f2000000/usb@19/disk@1:2,\System
Size/ GMT File/Dir
bytes date time TYPE CRTR Name
3/28/ 5 5:30:51 Installation
3/28/ 5 7:13:30 Library
ok
0 > dir /pci@f2000000/usb@19/disk@1:2,\System\Library\CoreServices
Size/ GMT File/Dir
bytes date time TYPE CRTR Name
82 3/28/ 5 6:55:33 ._Volume%20Name%20Icon
1445 8/ 4/14 18:49:47 tbxj chrp .disk_label
23 8/ 4/14 18:49:47 .disk_label.contentDetails
174276 3/28/ 5 6:55:35 tbxi chrp BootX
3/26/ 5 5:31:25 CharacterSets
....
Booting
To boot from a usb stick, we have to do:
0 > boot /pci@f2000000/usb@19/disk@1:2,\System\Library\CoreServices\BootX
- boot is the command to boot (which else ?)
- /pci@f2000000/usb@19/disk@1 is the path which identifies a USB stick.
- :2 this is the partition which contains the filesystem where is the boot loader
- , (comma) is a separator (which else ?)
- \System\Library\CoreServices\BootX is the path of the bootloader inside the filesystem.
- Note the use of the slash (/) as separator in the device tree elements, instead it is used the backslash as separator of the elements of a filesystem path
- the path of the disk and the partition number may vary depending of your configuration and disk partitioning.
To simplify a bit the things,we can use also the devalias aliases. For example we can do:
0 > dir usb1/disk@1:2,\System\Library\CoreServices
0 > dir hd:9,\
When using the "boot" command, instead of a fully path, you can pass "\\:tbxi". "\\" means the system folder, and ":tbxi" means a file type "tbxi". "\\:tbxi" is an alias for th Apple bootloader (which is under a system folder and it is marked as tbxi file type). But these are Apple/hfs+ specific things.
Conclusion
This post highlighted some concepts about the devices in the OpenFirmware. Also it has shown how boot a PowerMac from an usb stick.
In my opinion OpenFirmware is a very flexible firmware, and has a lot of capability.
I hoped to help a bit to understand how manage these capabilities.
Goffredo Baroncelli
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gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5
