Obscure opcodes

Tim Shoppa SHOPPA at trailing-edge.com
Thu May 11 22:37:50 AEST 2000

>>        LDUB, MED, XFC

>Back to 11/04/34a/44/60/70:
>med 076600

The MED instruction is used in RT-11 to determine if the machine is an
11/60.  It's probably also used in the 11/60-specific XXDP diagnostics.
I don't think that it's used in any of the -11 Unices.

Note that MED is really a two-word-long instruction.

>ldub 170003

My 11/60 Processor Handbook also lists MNS (170004), MNP (170005), and
MAS (170006).  These are "11/60 FP11-E Maintenance Instructions" and
"This set together with the LDUB instruction should be used for diagnostic
purposes only" according to the 11/60 book.

Note that no version of DEC MACRO-11 recognizes MNS, MNP, MAS, or LDUB.

The MED instruction is recognized in MACRO-11 only as MED6X.  The "6X"
jibes with the rumored existence of experimental variants on the 11/60
processor, one of which is the multi-processor 11/64.

 Tim Shoppa                        Email: shoppa at trailing-edge.com
 Trailing Edge Technology          WWW:   http://www.trailing-edge.com/
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