PCI Bridge Card

 The multiprocessor bus-to-PCI bridge is a special adapter that physically plugs into two sockets, one on the multiprocessor bus and one on the PCI bus. The circuitry on this card controls the movement of data between the processor complexes, memory cards and the I/O adapters on the Micro Channel and PCI buses. It implements a split bus design so that during slower I/O operations the multiprocessor bus can be made available for processor to memory transfers without having to wait on the I/O transfer.

PCI Bridge Card  FRU 75H9141 IPB Bridge card 
                                - use 33Mhz PCI bus clocking Date of 95

J3-6 Outlines only  JP1 Primary / Secondary Bridge  JP2 Program Enable

U1 Corollary PCIB 94C105A  U3 75H7487  1

JP1 is a three pin header. 1-2 is Primary bridge. 2-3 is Secondary bridge. 
JP2 is a two pin header 

PCI Bridge Card FRU 76H7134 Date of 94

CR2 Outline for LED CR3 LED JJ1 Primary / Secondary Bridge J3-17 Outline for headers U1,2 Corollary DPX 94C101B U3 Corollary CBC 94C102B U4,6 PALs

U5,21,24 PALs U12 1009-05 U13 1019-03 U14 1020-03 U15 1021-03 U16 1011-09 U17 1013-13

JJ1 Primary 1-2 (bottom) Secondary 2-3 (top)
 

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Symptom The PC Server 720 (8642) hangs or fails to boot. 

Fix  Inspect the EMC shield on the bridge card. Locate the metal clip (one of four) on the component side near capacitor C66. If the clip appears too close to capacitor C66, remove the EMC shield, and cut out the corner of the metal clip to increase the clearance from the capacitor
                (Recommended). 
                -OR- 
  Remove the EMC shield, and insulate the edge of the metal clip with electrical tape, and re-install the shield (Alternative). 
 --------------------------------------------------------------
| C-BUS II PCI BUS BRIDGE                ____   ____   ____    |
|   ASSY __________                     |    | |    | |    |   |
|     MADE IN U.S.A.                    |    | |    | |    |   |
|                                       |    | |    | |    |   |
|                                        ----   ----   ----    |
|                                        ____   ____   ____    |
|                                       |    | |    | |    |   |
|                                       |    | |    | |    |   |
|                                       |    | |    | |    |   |
|                                        ----   ----   ----    |
|     ____   ____   ____                                       |
|    |    | |    | |    |                                      |
|    |    | |    | |    |           ---  ---  ---  ---  ---    |
|    |    | |    | |    |          |   ||   ||   ||   ||   |   |
|     ----   ----   ----       _ _  ---  ---  ---  ---  ---  __|
-------------------------_____|_|______  ---   ---   ---   |
 |||||||||||| |||||||||||     | |      ||||| |||||||||||||||
 ------------ -----------     | |      ----- --------------
                             C66 C67

     Some bridge cards were undercut at the EMC shield attach point which  could cause a short to the C66 capacitor. 
 

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SUBJECT: INTERMITTENT HANGS - SERVER PC720(8642) 

SYMPTOM: 
Intermittent hangs / traps on Server 720 / 8642 

PROBLEM ISOLATION AIDS: 
Check settings of jumper J24 on system and manufacturing part number of PCI bridge card 

FIX: 
Bridge card 07H1107 (fru Part Number 71G0694) requires J24 on the system board to be open circuit 

Bridge card 75H7667 (fru Part Number 71G0694) requires J24 pins 1+2 to be Short circuit ( ie. the 2 pins of J24 nearest the back of the machine.) 

REASON : 
J24 pins 1+2 S/C sets the PCI bus speed to 33MHz. ( new Bridge card ) 
J24 pins o/c sets the PCI bus speed to 25MHz. ( old Bridge card )