The Computer
Guy's TroubleShooting
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The
Startup
Process
- How
your Macintosh starts up. How that
process can go wrong - the "Sad
Mac", the "Flashing ?", stalls,
freezes and error
messages.
Updated
8/28/99
|
Understanding a
process and it's design can improve your chances
of diagnosing and solving a problem. (not only
with computers, but autos and plumbing,
also)
|
- THE STARTUP PROCESS Part 1 of 2
- Power On - to - Welcome to Macintosh
- Startup Diagnostic
- As soon as the Mac is turned on, it runs a diagnostic
test stored in ROM (Read Only Memory). Part of the
Macintosh Operating System is in ROM as well. This part
of the Operating System is now software in iMacs and
G3s.
- The startup hardware diagnostic checks the memory,
boot blocks, and other componants. For example, the
diagnostic checks a specific location in the boot sector
that is written when the system is properly shut down. If
the computer was not shut down correctly the last time it
was on, the diagnostic will see this, display the
"Improper Shutdown Dialog Box" and perform a quick test
of the file structure of the hard drive. The improper
shutdown warning can be disabled in the General Control
Panel. If the diagnostic tests fail, the Macintosh will
halt startup and display the "Sad Mac" or a Flashing ?
DIsk Icon or System Folder icon.
- If you see any of these icons, there is a hardware or
software problem. The most common causes are:
- &emdash; Corrupted Boot Blocks
- &emdash; Corrupted System File
- &emdash; Corrupted System Enabler
- &emdash; Corrupted Font
- &emdash; Corrupted Finder File
- &emdash; SCSI Chain Errors
- &emdash; Faulty, conflicting, or incorrectly
installed memory chips
- &emdash; Faulty, conflicting, or incorrectly
installed expansion cards
- &emdash; Physically damaged hard drive or hard drive
interface
- &emdash; Corrupted or conflicting storage device
driver(s).
- &emdash; Physically damaged motherboard
- &emdash; Physically damaged power supply
- &emdash; Inadequate electrical power
- If a Macintosh boots and gives a "Sad Mac"
immediately, the problem is probably caused by either
faulty RAM, hardware or corrupted boot blocks. If the
"Sad Mac" occurs later in the startup sequence, there are
other problems.
- Power Key pressed or Power button/switch pressed
- Failure: grey desktop does not appear, no startup
chime
- Cause: PRAM battery dead, power cord loose, dead
power supply, keyboard not plugged in, keyboard
defective
- 1. Gray desktop pattern appears on
screen.
- A. The motherboard is tested
- Symptom: Sad Mac Icon
- &emdash;Cause: damaged motherboard or powersupply,
improperly seated card or ROM, conflicting ROMs
- &emdash;Repair: Reseat memory SIMMs, reseat Nubus or
PCI cards, find Authorized Service Center.
- B. The RAM is checked.
- Symptom: Sad Mac Icon
- &emdash;Cause: damaged RAM SIMM/DIMM, improperly
seated RAM Module, improper RAM SIMM order
- &emdash;Repair: Reseat all SIMMs, verify
configuration with GURU (Newer Technology) or Apple Spec
Database, remove SIMMs one at a time (on in pairs) and
test.
- C. The ROMs on Nubus or PCI cards is read and becomes
part of the system.
- Symptom: Sad Mac Icon or white box at top of
grey screen or splash screen of added video card
- &emdash;Cause: improperly seated card, conflicting
ROMs (normally happens at majorSystem Upgrade or computer
upgrade)
- &emdash;Repair: Remove cards and restart -
manufacturer may have ROM upgrade available (chips or
software)
-
- 2.. The SCSI bus is reset or initialized.
- Why: This is to make sure the bus was not left in a
bad state at shutdown or due to a crash.
- Symptom: Sad Mac Icon
- &emdash;Cause: improper termination, excessive cable
length, duplicate SCSI ID numbers, defective SCSI device
or cable.
- &emdash;Repair: Correct the problem. (See SCSI
Problems)
-
- 3. The SCSI port is checked.
- The Mac checks SCSI IDs (from 6 to 0) to find
attached drives and devices on the inbuilt SCSI chain. A
table is created tracking all connected disks and
devices. This is repeated for systems containing two or
more SCSI chains. For Ultra and Ultra2 SCSI ports the
device can have 15 ID's (from 14 to 0).
- For connected drives, the ROM boot code will use the
SCSI Manager to check SCSI partition information to
locate the driver . Partition information is checked to
ensure that the device is valid.
- These steps are repeated for each drive connected. At
this point, there may be a number of drivers in memory,
but there are no volumes, since none have been mounted
yet. There can be one driver for each drive, some drivers
will handle multiple drives.
-
- Loading the PRAM
- Startup Disk
- After the diagnostic test, the computer looks for a
startup disk. Any disk can be a startup disk (hard disk,
floppy disk, CD-ROM, etc) as long as it contains a
"blessed" system folder. If there is a diskette in the
floppy drive, the computer will check it first for a
blessed system folder. If it doesn't find one, the
Macintosh will eject the floppy and scan the SCSI chain
for a blessed system folder, starting with the internal
hard drive (SCSI ID #0).
- A startup disk's System folder must contain both a
System File and a Finder File. Some models running a
specific OS version also require a system enabler. Once
the computer finds a blessed System folder, it will begin
loading the operating system (ignoring any other System
files on the disk). On startup, the mac loads the
operating system files contained in the System Folder;
ignoring any other system files on the hard drive.
- When the computer searches for a bootable system
disk; it checks each disk's boot blocks for a "blessed"
system folder. When a System folder is "blessed" (System
Folder will have a small icon on it, if not blessed it
will be a plain folder), the folder's identification
number (all Macintosh folders are given a unique number
when they are cr eated) is written into the boot blocks.
As the Macintosh checks for a System folder, it finds the
ID number in the boot blocks and then checks the
specified folder for a System File and a Finder. The
process of writing the System folder's ID number into the
boot blocks is known as "Blessing" the System folder. If
the computer does not find a blessed System folder, it
will display the "flashing disk" icon:
- After the computer finds the Startup disk, it
searches for any additional devices attatched to the
computer. This is similar to how the Finder "mounts"
volumes when it is launched. Without specialized disk
drivers or utilities such as SCSI Probe, any devi ce not
recognised at this time cannot be addressed by the
computer. This is why all periferal devices should be
turned on before the computer itself; so they can be
recognised by the initial startup sequence.
-
- 4. Determine the startup disk.
- The startup device will be
- 1) Floppy (except on iMacs or newer models that do
not include a builtin floppy)
- 2) Designated Drive (Startup Disk Control Panel)
- 3) Internal SCSI Chain ID 6, 5, 4, 3, 2, 1, 0
- 4) External SCSI Chain ID 6, 5, 4, 3, 2, 1, 0 4 (if
it exists)
- 5) Additional SCSI Chain ID 6, 5, 4, 3, 2, 1, 0 4 (if
it exists) 14, 13, ... , 0 (if an UltraSCSI chain)**
- ** Except of certain proprietary cards (ie, Avid)
that limit the number of recognized drives
- This device selection is modified by keyboard
commands:
- Eject Floppy and removables at Startup [Mouse
Button]
- Bypass internal or normal startup drive
[CMD]+[OPTION]+[SHIFT]+[DELETE]
- Boot from CD (Late model Apples) [C]
- Mac OS8 - Starting a 68040 computers from a CD-ROM
using the c key may not work when the CD's SCSI ID is
5.
- Boot from a specific SCSI Drive
[CMD]+[OPTION]+[SHIFT]+[DELETE]+[#]
(# = SCSI ID#)
- Some Hard Drives require a longer time to become
available than the computer does and need to be turned on
first.
- If there is a floppy available it will always be the
startup disk. During this process the disk chosen as the
startup disk is not known to be valid. The System file
and boot blocks are checked later.
There isn't a search for floppy devices, the floppy
driver is contained in the ROM and will notify the System
when it detects one.The first floppy found will be used as
the startup disk. If there are multiple floppy drives, the
others will be mounted by the Finder. During the startup
sequence there is only one volume mounted (at execution of
the Macintosh boot blocks). The others are mounted by the
Finder.
- The Startup Disk Control Panel allows the user to
choose which device the system should try to boot from
first. The drive number, driver reference number, and
driver OS type are stored in PRAM to allow a chosen
device to be the boot disk. Remember, however, that the
floppy drives still have precedence over SCSI devices. If
the drive number that is stored as the Startup Disk is
invalid, or has a read/write error, the next disk in that
chain (or the next chain, if availble) will be chosen as
the next bootable candidate.
- Symptom: Flashing ? Disk Icon until viable
boot drive is found
- &emdash;Cause: Damaged Startup Disk's Boot Blocks or
System File or missing System FIle or enabler.
- &emdash;Repair: Boot from Emergancy Device and
replace the damaged System File or enabler OR reinstall
System Software.
-
- 5. Execute the Macintosh boot blocks.
- Once the Startup Disk has been determined, the boot
blocks are read from blocks 0 and 1 of the volume. The
boot blocks define various parameters in the system, such
as whether a debugger will be loaded, the name of the
startup program (not always the Finder), the size of the
event queue, the size of the system heap, and
others.
- After the boot blocks are read and verified, the
happy Mac icon is displayed . The happy Mac basically
means that valid Macintosh boot blocks were found.
-
Device Problems at Happy Mac
- Symptom: Flashing Happy Mac Icon replace by
Flashing ? Disk Icon
- &emdash;Cause: Damaged Startup Disk's System File or
System Enabler
- &emdash;Repair: Boot from Emergancy Device and
replace the damaged System File or enabler OR reinstall
System Software.
-
Symptom: Happy Mac appears briefly and
disappears, and then a floppy-disk icon (or system folder
icon on G3's and iMacs - which do not have a floppy
drive) appears with a blinking question mark.
- &emdash;Cause: Bad boot blocks, corrupted diskdata
structure, or corrupted system files.
- &emdash;Repair: Boot from Emergancy Device and
replace the damaged System File or enabler OR reinstall
System Software.
-
Symptom: Happy Mac flashes on and off; drive
does not boot.
- &emdash;Cause: Bad boot blocks or corrupted System
File or Enabler.
- &emdash;Repair: Run recovery program; reinstall Apple
System software.
-
Symptom: Happy Mac appears, but the drive seeks
repeatedly before bootinq.
- &emdash;Cause: Improper shutdown from a bomb, crash,
freeze or power outage &emdash; all file structures were
not properly updated before the crash. On the next
power-up, the Mac finds that the structureshave been left
in an unknown state and verifies them. This is the reason
for the long delay while the happy Mac is displayed. This
may cause no further problems.
- &emdash;Repair: Run Apple's Disk First Aid v8.2 or
newer to verify thedisk.
-
- Symptom: Flashing Happy Mac Icon replace by
Flashing ? Disk Icon
- &emdash;Cause: Newly installed CPU upgrade or
accelerator, PRAM is not consistant with new
configuration.
- &emdash;Repair: Zap PRAM with keyboard command or
TechTool (or similar utility) OR press the CUDA button on
motherboard. (See directions for upgrade or
accelerator)
-
- 6. Mount the Startup Device volume.
- If the mount fails, the process starts over at the
point where a startup, disk is being chosen (step 4
above) . The failing volume is removed from the list of
candidates.
- Symptom: Flashing Happy Mac Icon replace by
Flashing ? Disk Icon
- &emdash;Cause: Failure of designated Startup Disk's
Boot Blocks or System File
- &emdash;Repair: Run Norton Disk Doctor, TechTool Pro,
MacMedic, or Disk First Aid v8.2 or newer to verify
thedisk.
-
7. The System file is found and Working Directory
is created.
- The directory ID is set to the blessed folder. The
blessed folder is saved in the volume header as part of
the FinderInfo field. If the directory ID is wrong, the
System file won't be found, causing it to start over
again (at step 4).
- Symptom: Flashing Happy Mac Icon replace by
Flashing ? Disk Icon
- &emdash;Cause: Failure of designated System File or
Hard Drive Directory Damage
- &emdash;Repair: Run Norton Disk Doctor, TechTool Pro,
MacMedic, DiskWarrior or Disk First Aid v8.2 to verify
thedisk.
- If the Macintosh model is one that requires a system
enabler, it opens the enabler soon after it begins
loading the System file. If the enabler is not present, a
dialog will appear stating that the operating system is
not recent enough to run on the Macintosh.
- Symptom: Dialog box - This system is not
current and can not run on this Macintosh Model.
- &emdash;Cause: Missing or damaged System Enabler
- &emdash;Repair: Replace System Enabler, OR reinstall
System Software
- The System file is opened. If the file can not be
opened, the process starts over again (at step 4). The
Startup Screen is then loaded and displayed. If there is
no Startup Screen, the normal "Welcome to Macintosh"
message is displayed. Seeing a Startup Screen or
"Welcome..." means that the System file was found and
opened successfully. This is true for all but the Mac
Plus, SE, and other 64K ROM machines, where the Startup
Screen is displayed before the System file is
opened.
-
- David Anders The Computer Guy 206-286-8438
DavidA3292@aol.com
- Copyright © 1998 David Anders The
Computer Guy
-
- Top of
Page
- Startup
Part 2 of 2
Email your Corrections
and Comments.
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