chlebana@physics.utoronto.ca (Frank Chlebana) (04/30/91)
I am using Programmed IO to read data from an external VME crate into local memory of the 4D/35S. The cpu executes load and store instructions from/to the bus extender registers to/from local memory. The bus extender I am using does not operate as a VME master, so I cannot use it as a DMAC. To do the transfer I use a similiar routine as bcopy(). Prior to the transfer splhi() is set, so the machine is virtually dedicated to the transfer. On the 4d/25s I was able to get the following transfer rates reads 4.3 MB/s writes 3.8 MB/s On the 4d/35s the rates are reads 2.6 MB/s writes 2.8 MB/s These are typical times for a 2047 longword transfer, where 1 MB==2**20. Am I missing some "trick" that can be used to increase the transfer rates when I access a VME slave? Can the 4d/35s initiate DMA from VME slaves?? Frank Chlebana chlebana@oldkat.physics.utoronto.ca