On 03/07/11 23:57, allison<ajp166 at verizon.net> wrote: Actually, Tony is totally correct. There was an EAE for the PDP-11 as well, and it is a Unibus device, with a few registers in floating space. You load some of them with the arguments, and then read out the result at another register a little later. It was produced before the EIS came about, and probably only sold with the 11/20 and 11/15. But it should work on any Unibus machine. FIS first came on the 11/40. The same opcode space was then reused for the FPP on the 11/45 and onwards. 11/23 never had FIS, but the 11/03 did. 11/23 had an optional FPP chip, however (and CIS). In fact, the only two machines to have FIS was the 11/40 and 11/03 (and I know the 11/35 as well, but that is just a derivative of the 11/40). Why the 11/03 got FIS is beyond me, but maybe they didn't have enough transistors to implement the FPP, but wanted something, and reused that design instead, since you at least have some software that supports it. I'm pretty sure the FIS for 11/03 was an option, though, and not included in every machine. The FIS for the 11/40 definitely was. As far as integer multiply/divide goes, the 11/40 had EIS as well, but it was optional. Just like FIS. Johnny