This code is resonsible for testing the computers integrity on startup, initializing devices, and providing code for input/output functions that allow the Operating System proper to be found, loaded, and executed.
Open Firmware(OF) stores a number of setings in non-volatile battery backed storage(NVRAM) that can be used to configure the boot process. OF also has a built in 'monitor' that allows us to interact with it in order to display and modify these parameters with no other operating system loaded.
This monitor can be accessed by holding down a combination of four keys simultaneously during the boot process. To do this, reboot or reset the machine and hold down the Command, Option, 'O', and 'F' keys simultaneously. You need to hold these keys down when you hear the boot-chime until the Open Firmware prompt appears. The boot-chime can not always be heard however, depending on the state of the sound device. NOTE: The "command" key is the one with the apple and clover leaf symbols printed on it. The "option" key should be right next to it and has a funny two line symbol and "alt" printed on it, at least on this keyboard.
To see all settings, type "printenv" at the OF prompt.
-- BEGIN PASTE -- 0 > printenv -------------- Partition: common -------- Signature: 0x70 --------------- little-endian? false false real-mode? false false auto-boot? true true diag-switch? false false fcode-debug? false false oem-banner? false false oem-logo? false false use-nvramrc? false false use-generic? false false default-mac-address? false false real-base -1 -1 real-size -1 -1 load-base 0x800000 0x800000 virt-base -1 -1 virt-size -1 -1 pci-probe-mask -1 -1 screen-#columns 100 100 screen-#rows 40 40 selftest-#megs 0 0 boot-device enet:0,bootme,,,2 hd:,\\:tbxi boot-file boot-screen console-screen diag-device enet enet diag-file ,diags ,diags input-device keyboard keyboard output-device screen screen input-device-1 scca scca output-device-1 scca scca mouse-device mouse mouse oem-banner oem-logo nvramrc boot-command mac-boot mac-boot default-client-ip default-server-ip default-gateway-ip 192.168.2.1 default-subnet-mask default-router-ip boot-script aapl,pci Use PRINT-AAPL,PCI to view ASVP 30313037 333f3030 35363e33 medusa 74727565 snakebitecpu0 70617373 6564 snakebitecpu1 70617373 6564 ok -- END PASTE --
The right hand column shows the default setting, while the left hand column shows the current settings as set up for use in the cluster.
Note in particular the 'boot-device', and the 'default-gateway-ip', settings. These are described in detail in bootsettings.html
[ We are able to tell Open Firmware what device to boot from. Most convenient for us it to boot from the ethernet device, thus allowing us to control the booting from a remote machine on the network. This remote machine will then become our cluster control server. ]
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