ded@aplvax.UUCP (Don E. Davis) (07/25/86)
References: Ultrix-32m has a /sys/vaxuba directory and supports kernal routines such as ubago() and ubadone() even though the MVII is a Q bus rather than a Unibus machine. This makes it nice for those of us who have to port drivers from VAX 780's. Or at least it should. I've encountered a strange problem during DMA. Every now and then, a 4 byte DMA will fail. I'll get an interrupt from the MDB DR11W board saying the DMA has completed, but the contents of the target memory location will not have been changed (even though the board CSR says READY). One of the things I monitored during debugging was the address generated by the ubago() routine to my dgo() function. For several transfers in a row, it will give me an address of, say, 167734 (where 167 is a map register and 734 is the page offset). Then the address will change to 210734 and the DMA will fail. The change of address always seems to precede the failure of the DMA. I am locking pages in memory with vslock(). Has anyone seen anything like this before? -- Don Davis JHU/APL ...decvax!harpo!seismo!umcp-cs!aplcen!aplvax!ded ...rlgvax!cvl!umcp-cs!aplcen!aplvax!ded