An FPF11 can be used with a KDF11-B (11/23+), which is a Qbus machine. It can also be used in an 11/24, it derives only power from the bus (if I remember correctly). I would suspect that it might also work with an 11/23 (KDF11-A), since it has the same chip location for Floating point as the 11/23+, but I've never confirmed this. Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com | | Unix Support Engineering Group | (home): mbg!world.std.com | | Compaq Computer Corporation | addresses need '@' in place of '!' | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+