I believe the CMD controllers are supposed to be the fastest, something else to consider is that the Q-Bus itself is only something like 3.5MB/Sec (does anyone happen to remember the exact numbers). If I can find the time, I can run a test under RT-11 on my PDP-11 (Viking QDT). Zane -- -- | Zane H. Healy | UNIX Systems Administrator | | healyzh at aracnet.com (primary) | OpenVMS Enthusiast | | | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |