I would think that it shut down due to a kernel panic, but I don't have all the details. From what I read, it started to load, and then panicked, which could lead to a shutdown sequence initiated by the kernel.
PRAM is (physically) 'poor mans' NVRAM': it is Battery-backed RAM (BBR), and sending the
open-apple + option + P + R command tells the firmware to
clear its contents. You clear corrupted PRAM just as you did to resolve this, and in no other manner. The
actual components (
i.e. the physical RAM ICs) aren't corrupted:
Only the memory record is corrupted.
Real NVRAM generally falls into two categories: Bubble Memory (if anyone remembers this), and NAND memory, which
may be on newer models of Apple HW, but is not used on any PowerPC model.
Essentially, you have SRAM, or DRAM, or SDRAM, that has a battery for power when the system is off, and relies on main power when the system is on; else it would quickly kill the battery. Thus, the more often the system is running, the less you use your battery, and conversely, the less-often that your system is running, the more you rely on the backup battery.
Most systems use a flat cell battery, similar to those used in watches, and clocks. Some systems have a cylindrical battery module, and a few have a battery that is soldered into position (usually not Apple systems). The original Mac, through the Mac Plus, used a AA battery, behind a cover, on the rear of the unit, behind the monitor, that you could access without opening the system.
PRAM has been around
that long, and is essentially a successor to the RTC cards in the Apple II days. The //gs used a
form of PRAM that held system settings, for slot definitions and arrangements, screen colour settings, etc..
As the systems evolved, more and more settings were allocated to PRAM, with the following being
typical, although possibly not an absolute list:
32-bit addressing (Classic, System 7-specific for M680x0 systems).
Alarm clock setting (Classic only; not OSX).
AppleTalk settings (may be Classic-only).
Application font (Classic only; not OSX)
Autokey rate and delay.
Battery/Power management scheme (for laptops).
Caret blink rate (may be Classic-only).
Charmap settings.
Desktop pattern (Classic only; not OSX)
Disk cache (An important setting, that if corrupted causes all sorts of mayhem.)
DVD region settings (stored for universal application access; you cannot change the value).
Highlight colour (Classic only; not OSX)
Lockdown firmware password (not all models).
Menu blink count (Classic only; not OSX).
Monitor configuration and display settings (Classic only; not OSX)
Mouse and trackpad settings, including click rate, tracking, acceleration, etc..
Network settings (Classic only; not OSX)
RAM disk (Classic primarily; RAM Disks in OSX are handled differently)
Recent kernel panic logs.
Screen resolution and colour depth.
Serial printer settings (may be Classic-only).
Serial-Port configurations and settings (may be Classic-only).
Sound input settings.
Speaker output volume.
Startup disk (a very important setting).
System sounds (Classic only; not OSX)
Time, date, timezone, and region settings.
Virtual memory (Classic only; not OSX).
The actual PRAM values differ based on the
model of Macintosh, so some or many of these may not apply to a specific case.
Another command, similar to
open-apple + option + P + R is the command
to reset NVRAM, and is reset with
open-apple + option + N + V. This too, may be model-specific, and not all Mac models can execute this command.
NVRAM holds more low-level information, such as:
Boot beep, error beep
Open Firmware
POST (Power-on Self Test)
ROM diagnostics
Tied to PRAM, it stores the values for:
aapl,tdm-units
ASVP
auto-boot
boot-args
boot-command
boot-device
boot-screen
boot-script
boot-volume
console-screen
default-client-ip
default-gateway-ip
default-mac-address
default-router-ip
default-server-ip
default-subnet-mask
diag-device
diag-file
diag-switch
fcode-debug
input-device
input-device-1
little-endian
load-base
logger-base
mouse-device
oem-banner
output-device
output-device-1
pci-probe-mask
playform-uuid
prev-lang
ram-size
real-base
real-size
screen-#columns
screen-#rows
scroll-lock
selftext-#megs
skip-netboot
use-generic
use-nvramrc
virt-base
virt-size
Some systems may store other values, and these are valid for NWR (Open-Firmware) Macs. OWR Macs, from the Platinum G3 desktop, and Platinum G3 tower systems, back to the original Macintosh, do not have these NVRAM-specific settings, and rely on PRAM settings.
Resetting PRAM usually
also resets NVRAM, but I believe that resetting NVRAM only using the
open-apple + option + N + V command does not always affect PRAM. (See
this article on NVRAM
While it is
possible in theory to have faulty PRAM chips, in thirty years of repairing Mac HW, I have
never once seen that problem. I have had to replace my share of batteries, which is wise to do every so often (
e.g. five-year to ten-year intervals in my case).
For Ubuntu on PowerPC, you may want to read
this FAQ.
Note that I disagree with using 12.04, from various personal experiences of it panicking, or drivers not working. 10.04 LTE is really the widest, best-supported Linux PPC flavour;
YDL 7 would be my second choice.
