Backplane
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Backplane Signal Assignments

There are two 96-pin connectors.  I'll call them "left" and "right" assuming you are viewing the card facing the connector edge with the component side up.  Each connector is broken down into three 32-pin sections, labelled "A", "B" and "C".  Note that when viewing the pins coming out of the backplane, "C" is on top, "B" in the middle and "A" on the bottom (despite what the wire-wrap tags say)

Left A

1 L0 Rcard Buffered output
2 L1 Rcard Buffered output
3 L2 Rcard Buffered output
4 L3 Rcard Buffered output
5 L4 Rcard Buffered output
6 L5 Rcard Buffered output
7 L6 Rcard Buffered output
8 L7 Rcard Buffered output
9 L8 Rcard Buffered output
10 L9 Rcard Buffered output
11 L10 Rcard Buffered output
12 L11 Rcard Buffered output
13 L12 Rcard Buffered output
14 L13 Rcard Buffered output
15 L14 Rcard Buffered output
16 L15 Rcard Buffered output
17 MAR0 Rcard Unbuffered 2-state output
18 MAR1 Rcard Unbuffered 2-state output
19 MAR2 Rcard Unbuffered 2-state output
20 MAR3 Rcard Unbuffered 2-state output
21 MAR4 Rcard Unbuffered 2-state output
22 MAR5 Rcard Unbuffered 2-state output
23 MAR6 Rcard Unbuffered 2-state output
24 MAR7 Rcard Unbuffered 2-state output
25 MAR8 Rcard Unbuffered 2-state output
26 MAR9 Rcard Unbuffered 2-state output
27 MAR10 Rcard Unbuffered 2-state output
28 MAR11 Rcard Unbuffered 2-state output
29 MAR12 Rcard Unbuffered 2-state output
30 MAR13 Rcard Unbuffered 2-state output
31 MAR14 Rcard Unbuffered 2-state output
32 MAR15 Rcard Unbuffered 2-state output

Left B

1 +5    
2 Gnd    
3 IR0 Ccard Unbuffered
4 IR1 Ccard Unbuffered
5 IR2 Ccard Unbuffered
6 IR3 Ccard Unbuffered
7 IR4 Ccard Unbuffered
8 IR5 Ccard Unbuffered
9 IR6 Ccard Unbuffered
10 IR7 Ccard Unbuffered
11 PRIV Ccard raw mcode bits
12 Gnd    
13 +5    
14 L_FAULT Ccard High active, clocked
15 ENCODER0 Ccard Priority encoder 0
16 ENCODER1 Ccard Priority encoder 1
17 ENCODER2 Ccard Priority encoder 2
18 ENCODER3 Ccard Priority encoder 3
19 _STOP_CKS FPcard  
20 MEMREF Ccard High active, not clocked
21 LATCH_SZ Ccard Raw mcode bits
22 Gnd    
23 MSWP Rcard Unbuffered
24 MSWE Rcard Unbuffered
25 MSWD Rcard Unbuffered
26 MSWM Rcard Unbuffered
27 MSWV Rcard Unbuffered
28 MSWS Rcard Unbuffered
29 MSWC Rcard Unbuffered
30 MSWZ Rcard Unbuffered
31 Gnd    
32 +5    

Left C

1 A0 Mcard/Dcard Always buffered
2 A1 Mcard/Dcard Always buffered
3 A2 Mcard/Dcard Always buffered
4 A3 Mcard/Dcard Always buffered
5 A4 Mcard/Dcard Always buffered
6 A5 Mcard/Dcard Always buffered
7 A6 Mcard/Dcard Always buffered
8 A7 Mcard/Dcard Always buffered
9 A8 Mcard/Dcard Always buffered
10 A9 Mcard/Dcard Always buffered
11 A10 Mcard/Dcard Always buffered
12 A11 Mcard/Dcard Always buffered
13 A12 Mcard/Dcard Always buffered
14 A13 Mcard/Dcard Always buffered
15 A14 Mcard/Dcard Always buffered
16 A15 Mcard/Dcard Always buffered
17 A16 Mcard/Dcard Always buffered
18 A17 Mcard/Dcard Always buffered
19 A18 Mcard/Dcard Always buffered
20 A19 Mcard/Dcard Always buffered
21 A20 Mcard/Dcard Always buffered
22 A21 Mcard/Dcard Always buffered
23 CODE_PTB Ccard raw mcode bits
24 USER_PTB Ccard raw mcode bits
25 DBUS0 All cards Always buffered
26 DBUS1 All cards Always buffered
27 DBUS2 All cards Always buffered
28 DBUS3 All cards Always buffered
29 DBUS4 All cards Always buffered
30 DBUS5 All cards Always buffered
31 DBUS6 All cards Always buffered
32 DBUS7 All cards Always buffered

Right A

1 ALUOP0 Ccard Raw mcode bits
2 ALUOP1 Ccard Raw mcode bits
3 USE_CARRY Ccard Raw mcode bits
4 ALUOP_SZ Ccard Raw mcode bits
5 IMMVAL0 Ccard Raw mcode bits
6 IMMVAL1 Ccard Raw mcode bits
7      
8 L_PTB Ccard NOR(decoded[LATCH],NCLKS)
9 Gnd    
10 L_FPL Ccard Front Panel L latch signal
11 Gnd Ccard  
12 _ER_MDR Ccard Decoded ER mcode bits
13 _ER_IMM Ccard Decoded ER mcode bits
14 _ER_FAULTCODE Ccard Decoded ER mcode bits
15 Gnd    
16 _SET_FLAGS Ccard Decoded MISC mcode , unclocked
17 Gnd    
18 INIT_INST Ccard Active high, clocked
19 Gnd    
20 _EL_PTB Ccard Decoded EL mcode bits
21 _EL_MAR Ccard Decoded EL mcode bits
22 _EL_C Ccard Decoded EL mcode bits
23 _EL_PC Ccard Decoded EL mcode bits
24 _EL_DP Ccard Decoded EL mcode bits
25 _EL_SP Ccard Decoded EL mcode bits
26 _EL_A Ccard Decoded EL mcode bits
27 _EL_B Ccard Decoded EL mcode bits
28 _EL_MDR Ccard Decoded EL mcode bits
29 _EL_SSP Ccard Decoded EL mcode bits
30 _EL_TPC Ccard Decoded EL mcode bits
31 _EL_MSW Ccard Decoded EL mcode bits
32 +5    

Right B

1 L_EI Ccard NOR(decoded[MISC],NCLKS)
2 L_MODE Ccard AND(raw mcode,CLKS)
3 L_PAGING Ccard AND(raw mcode,CLKS)
4 L_MAR Ccard AND(raw mcode,CLKS)
5 L_MDR_LO Ccard raw mcode (and'd w/ CLKS on Rcard)
6 L_MDR_HI Ccard raw mcode (and'd w/ CLKS on Rcard)
7 L_MSW Ccard NOR(decoded[LATCH],NCLKS)
8 L_C Ccard NOR(decoded[LATCH],NCLKS)
9 L_PC Ccard NOR(decoded[LATCH],NCLKS)
10 L_DP Ccard NOR(decoded[LATCH],NCLKS)
11 L_SP Ccard NOR(decoded[LATCH],NCLKS)
12 L_MDR Ccard NOR(decoded[LATCH],NCLKS)
13 L_SSP Ccard AND(LSP,OR(MSW[intrap],!MSW[mode]))
14 L_A_LO Ccard NOR(decoded[LATCH],NCLKS) 
15 L_A_HI Ccard NOR(decoded[LATCH],NCLKS) & LATCH_SZ
16 L_B_LO Ccard NOR(decoded[MISC],NCLKS)
17 L_B_HI Ccard NOR(decoded[MISC],NCLKS) & LATCH_SZ
18 FAULT_PENDING    
19 _L_PTE Ccard OR(decoded[MISC],NCLKS)
20 Gnd    
21 L_IN_TRAP Ccard NOR(decoded[MISC],NCLKS)
22 IN_TRAP Ccard FF on Ccard
23 Gnd    
24 NEXT0 Card Microcode next address
25 NEXT1 Card Microcode next address
26 NEXT2 Card Microcode next address
27 NEXT3 Card Microcode next address
28 NEXT4 Card Microcode next address
29 NEXT5 Card Microcode next address
30 NEXT6 Card Microcode next address
31 NEXT7 Card Microcode next address
32 +5    

Right C

1 _NP Mcard Unclocked, memref & page not present
2 _NW Mcard Unclocked, memref & write & page not writeable
3 _HALT Ccard Unclocked, decoded MISC
4 COMMIT Ccard Clocked, decoded MISC | INIT_INST
5 _TRAPO Ccard Unclocked, decoded MISC
6 _DO_BRANCH Ccard Unclocked, decoded MISC
7 _DO_RSHIFT Ccard Unclocked, decoded MISC
8 _RESET External  
9 Gnd    
10 E_MDR_LO Ccard Inverted raw mcode
11 E_MDR_HI Ccard inverted raw mcode
12 _IRQ0 External Active low
13 _IRQ1 External Active low
14 _IRQ2 External Active low
15 _IRQ3 External Active low
16 _IRQ4 External Active low
17 _IRQ5 External Active low
18 FP_RAM Pcard Toggle, high if RAM, low if ROM
19 _DMA_REQ External Active low
20 _DMA_ACK Ccard Unclocked, decoded MISC
21 FP_L0 Ccard Front panel select
22 FP_L1 Ccard Front panel select
23 FP_L2 Ccard Front panel select
24 FP_L3 Ccard Front panel select
25 _RW Ccard unclocked, 0 is read
26 MEMORY Mcard 0 for device, 1 for memory
27 _E_PTE Ccard Unclocked, decoded MISC
28 _FP_WRITE Pcard Debounced write pb, low active
29 EXT_CLK Ccard External clock
30 CLKM Ccard microcode clock
31 CLKS Ccard system clock
32 +5