Subject: JMS I Z 10?

From: [email-masked]
Date: 18 Jan 94 16:35:29 MDT

Greetings!

As I mentioned earlier, I've been fussing about on and off with building a
PDP-5 inside a Xilinx. One thing that's always stymied me, though, is handling
an indirect JMS through an autoindex register. I've not figured out how to
do it without using an extra register (I've toyed with using the accumulator,
but decided that clearing the accumulator was not a good side effect for the
JMS instruction).

Any software out there that actually does a JMS I Z 10?
-- 
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Roger Ivie      | Don't think of it as a 'new' computer, think of it as
[email-masked] |     'obsolete-ready'

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From: [email-masked] (Charles Lasner)
Date: 19 Jan 1994 12:56:32 GMT

>Any software out there that actually does a JMS I Z 10?

Yes, diagnostics.  The hardware guys were always testing odd cases that
weren't mainstream coding techniques.  Occasionally, some of their ideas
became part of the "regular" software!

I don't have a particular example, but here's a counter-example taken from
the -8/e EAE diagnostic:

In mode B EAE, the MUY instruction does *not* take its argument in-line
(as in mode A) but rather the next word is a *pointer* to the argument. 
The diagnostic places the MUY instruction into 00007 and dares the
hardware to screw up on both the DF and auto-index implications of the
reference to 00010 in the deferred state.

I *almost* used the notion of placing a DLD;xxxx sequence into locations
00016-00017 as part of a subroutine to pull in a DP list off a pointer,
but it doesn't work the way I want it to!  Unfortunately, they auto-index
(as expected!) the c(00017) but then copy the pointer address data into an
internal register.  Thus, it's only good if you want to "half"-increment
your way through a list of DP values.  (Perhaps this could be useful! 
Just wasn't to me at the time!)

cjl