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Appendix B: Challenge DMA with Multiple IO4 Boards
In late 1995 a subtle hardware problem was identified in the IO4 board that is the primary I/O interface subsystem to systems using the Challenge/Onyx architecture. The problem can be prevented with a software fix. The software fix is included in all device drivers distributed with IRIX 6.2 and a software patch is available for IRIX 5.3. However, some third-party device drivers also need to incorporate the sofware fix. This appendix explains the IO4 problem as it affects device drivers produced outside Silicon Graphics.
The issue in a nutshell: if you are responsible for a kernel-level device driver for a DMA device for the Challenge/Onyx architecture, you probably need to insert a function call in the driver interrupt handler.
- The IO4 Problem
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- Fixing the IO4 Problem
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