Apple mac pro User Manual

Mac Pro Troubleshooting — General Information 141
DIMMs for Mac Pro must fit these specifications:
667 MHz, FB-DIMMs• 
72-bit wide, 240-pin modules• 
36 devices maximum per DIMM• 
Error-correcting code (ECC)• 
Important: For proper operation of Mac Pro computers, Apple recommends using only Apple-
approved Mac Pro FB-DIMMs. Refer to GSX for Apple FB-DIMMs service part numbers.
PCI Express Cards
The Mac Pro logic board includes one double-wide PCI Express graphics slot and three PCI 
Express expansion...

Mac Pro Troubleshooting — General Information 142
Cable, Connector and Signal MatrixCABLE DESCRIPTION
Service PN
LENGTH (mm)
LENGTH (in)
MLB CONN LOCATION
MLB CONN LABEL
MLB CONN DESCRIPTION
CONNECTOR 2 DESCRIPTION
CONNECTOR 3 DESCRIPTION
CONNECTOR 4 DESCRIPTION
CONNECTOR 5 DESCRIPTION
POWER / SIGNALS CARRIED
HDD SATA
P art of 922-7682
450
17.7
B -1
SATA
36-pin high-densit y
7-pin flat to HDD 1
7-pin flat to HDD 2
7-pin flat to HDD 3
7-pin flat to HDD 4
Serial A TA signals to/from all four HDDs and main...

Mac Pro Troubleshooting — General Information 143
Cable Connector Locations
Use the diagram below to find the location of the internal cable connectors on the logic board.
A        B       C        D        E        F        G       H        J   \
      K
A 
       B       C        D        E        F        G       H        J   \
      K
1 2 3 4 5 6 7 8 9
12 3 4 5 6 7 8 9
Thermal Calibration
Unlike in earlier Power Mac G5 computers, replacing a processor in a Mac Pro computer does not 
require running...

Mac Pro Troubleshooting — General Information 14 4
Block Diagram
The architecture of the Mac Pro is based on two dual-core Intel Xeon processors, the North 
Bridge memory controller and the South Bridge I/O controller, as shown in the simplified block 
diagram below. 

Mac Pro Troubleshooting — General Information 145
Resetting the Logic Board
System Management Controller (SMC) Reset
The System Management Controller (SMC) is a chip on the logic board that controls all power 
functions for the computer. If the computer is experiencing any power issue, resetting the SMC 
may resolve it. The SMC controls several functions, including:
Telling the computer when to turn on, turn off, sleep, wake, idle, and so forth• 
Handling system resets from various commands• 
Controlling...

Mac Pro Troubleshooting — General Information 146
Real Time Clock (RTC) Reset
The Real Time Clock (RTC) is a chip on the logic board that controls the date and time functions 
of the computer. If the computer is experiencing an issue booting, resetting the RTC may resolve 
it. Follow these steps to reset the RTC:
From the Apple menu, choose Shut Down (or if the computer is not responding, hold the 1. 
power button until it turns off ).
Unplug the AC power cord.2.  
Remove the battery for at least 20...

Mac Pro Troubleshooting — General Information 14 7
Diagnostic LEDs
The Mac Pro logic board includes a set of LEDs to help service providers troubleshoot the 
computer. The LEDs are located toward the rear of the logic board, under the memory cage, next 
to PCI card slot 1. You can view these LEDs by removing the computer’s side access panel and 
looking through the memory cage to the logic board below. LEDs 2, 3, 4, and 5 are normally off 
and will automatically illuminate if an error occurs. To read...

Mac Pro Troubleshooting — General Information 14 8
Use the following table to interpret the LEDs.
LocationNameColorNominalPress DIAG_
LED button 
to display
Indicates
Led 1Trickle PwrYellowOnYe sPower supply 
is providing 
trickle power
Led 2CPU B ErrorRedOffNoCPU B halts 
on an IERR 
(instruction 
error)
Led 3CPU A ErrorRedOffNoCPU A halts 
on an IERR 
(instruction 
error)
Led 4CPU B OTRedOffNoCPU B is over 
temperature
Led 5CPU A OTRedOffNoCPU A is over 
temperature
Led 6GPU PresentGreenOnYe sEFI has...

Mac Pro Troubleshooting — General Information 149
LED 2 CPU B (Lower Processor) Error 
LED 3 CPU A (Upper Processor) Error
Normally off. These LEDs come on if an error occurs or if the BootROM is corrupted. They do not 
depend on the DIAG_LED button being pressed.
Related symptoms include no video or the computer is hung up. If the BootROM is corrupted, 
the optical drive tray should eject, prompting for the insertion of a recovery disc to restore the 
BootROM.
Troubleshooting: 
With the computer booted,...

Mac Pro Troubleshooting — General Information 150
Replace the processor associated with the corresponding LED.• 
LED 6 GPU Present
Normally on when DIAG_LED button is pressed. 
If this LED is on, it indicates there is a graphics card installed and recognized by the computer. 
It does not indicate that the graphics card is fully functional. Some graphics cards require 
additional power to function, which is available from connectors on the logic board. For these 
cards, if the auxiliary booster power...