Without the TMP on the Nicolet MEMA ARGONE ANDA ARGTWO LASH 1 ANGA A+MA ARGONE A+MA ARGTWO ( or A+MM ARGTWO to save in ARGTWO )
The link bit isn't used by LASH or adds on the Nicolet. It is only the carry out of an add. It is a little more clumsy to use as a carry. It can only be used as a condition of a skip or execute. ________________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Don North <no...@alum.mit.edu> Sent: Wednesday, December 23, 2015 11:21 PM To: cctalk@classiccmp.org Subject: Re: Has Anyone Written PDP-8 .XOR. Code Using the MQ Register (Without the EAE)? On 12/23/2015 10:50 PM, Don North wrote: > On 12/23/2015 7:14 PM, Christian Gauger-Cosgrove wrote: >> On 23 December 2015 at 13:44, CLASystems <clasyst...@gmail.com> wrote: >>> Ironically, the shortest and fastest seems to be avoidance of the MQ >>> altogether [thus making it work on ANY model]. >>> >>> TAD ARGONE >>> AND ARGTWO >>> CLL RAL >>> CIA >>> TAD ARGONE >>> DCA ARGTWO >>> >>> This works because .XOR. is addition ignoring the carry bits. So, knowing >>> they will happen, just allow them at first, then remove them. >>> >> Hmm, I just tried that in SIMH, and that doesn't XOR at all. > I think there was just a bit of brain fade in the original listing. From > DEC-08-FFAA-D PDP-8 Math Library circa 1968 > the XOR routine is as follows, transcribed to SIMH: > > sim> de 76 1234 > sim> de 77 4321 > sim> ie -m 100-107 > 100: CLA CLL > 101: TAD 76 > 102: AND 77 > 103: CIA > 104: CLL RAL > 105: TAD 76 > 106: TAD 77 > 107: HLT > sim> go 100 > > HALT instruction, PC: 00110 (AND 0) > sim> ex ac > AC: 5115 > > Which produces the correct result in the AC. Locations 103/104 were swapped in > order, and location 106 was left out. > And for completeness location 100 was added to initially clear the AC/Link. > > Don > FYI here is a link to find the document: http://manx.classiccmp.org/details.php/1,3191 I can't find it under dec/pdp8 on bitsavers, maybe I'm just not seeing it. Don
