IBM BDM-610000049 - Manual (Page 62)

52 CMX158886 cpuModule BDM-610000049 Rev G
Bridge Link (CN4)
The Bridge Link connector allows devices that requires Legacy/ISA interrupts to interface with the cpuModule.
When ISA devices are installed in the system (via a PCI to ISA bridge card), the Bridge Link connector provides
Legacy/ISA DMA request signals, as well as a serial interrupt signal which permits access to all available system
interrupts.
Multiple devices may utilize the serial interrupt signal, SERIRQ, which is decoded on the cpuModule. Only one
device may use the DMA request and grant signal pair.
Facing the connector pins, the pinout is:
Table 34 Bridge Link (CN4)
Pin Signal Function
1 GND Ground
2 DMAREQ Legacy/ISA DMA Request
3 SERIRQ Serial Interrupt Request
4 DMAGNT Legacy/ISA DMA Grant
3 1
SERIRQ GND
DMAGNT DMAREQ
4 2