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AST RESEARCH TECHNICAL BULLETIN TB-0151A 04-11-86
AST COMMUNICATION BOARDS WITH THE IBM AT AND COMPATIBLES
AST communication boards use IRQ2 as a factory default interrupt
setting. The IBM AT, the COMPAQ 286, and the COMPAQ DESKPRO 286
have two interrupt controller chips: 8259's. IRQ2 is on
Interrupt Controller, CTLR2, and is a cascading interrupt. A
cascading interrupt has to travel a longer route before it is
serviced. Because of this, there may be differences in timing
between a cascading and non-cascading interrupt. Problems may
occur if the interrupt takes a longer time to be serviced than
the communication software expects.
For this reason, AST suggests that the AST board is set for an
unused non-cascading interrupt.
The following AST communication packages use IRQ2: AST-5251/11,
AST-5251/12, AST-3780, AST-3770, AST-BSC, AST-BSC CLUSTER, AST-
BSC GATEWAY, AST-SNA, AST-SNA CLUSTER, and AST-SNA GATEWAY.