err, any refs for that? I really doubt it but could well be wrong. I'm not aware of any mainstream arch that can/could do that, that I can think of.

At least the IBM System/370 (not 360 as I said above) had assembly instructions that took memory addresses directly without a register or immediate being in the instruction.

Here is an example of such an instruction from the

"AP, Add Packed (Decimal) The data string located at the storage address specified by operand-2 (b2+d2) is added to the data string located at the storage address specified by operand-1 (b1+d1). Operand-2 remains unchanged."

http://www.simotime.com/asmins01.htm#AP

Now, how this was actually done in hardware I don't know, but I would not be surprised if hidden registers were involved. So, maybe this is not really an example that fits the original premise of this subthread, but I think it is interesting nevertheless.