NOPE NOT A BIG RTE PERSON - BUT YES THERE WOULD BE MULTI SERIAL BOARDS IN SOME INCOMING PROCESSORS RAN IT ONCE AND PLAYED WITH IT... BROKE 1000 SYSTEMS DOWN AND SOLD THE PIECES. THE ONLY SYSTEMS THAT WE SUPPORTED SOFTWARE WISE WERE F AND THEN ACCESS THIS 21 WHATEVER IS THE SKINNY ONE! DOUBLE SIDED KEY - AND IF I REMEMBER WILL YANK IT UP OFF THE FLOOR IN MY OFFICE TOMORROW AND SEE THE # BUT SUSPECT 2108 AS ABOUT ALL I REMEMBER LIKING ABOUT IT WAS IT HAD THE BOOT BUILT IN ,GRIN!. WHAT I DID NOT LIKE WAS IT WAS NOT CORE MEMORY. SURE WERE FUN TIMES... ALTHOUGH THERE WAS ALWAYS A FOND SPOT FOR THE 21XX STUFF... I GOT REALLY OCCUPIED WITH THE 3000 AS A COMPUTER THAT I WOULD REALLY USE. IN THE EARLY DAYS OF RUNNING THE ACCESS THOUGH WHAT GREAT FUN AND THE 100 BOARD BBS/MULTI USER CHAT/VOTE AND POL/EMAIL AND MOST GAMES WE DID GOT MOVED TO THE 3000. ED - WHOSE KEYBOARD THINKS IT IS AN ASR 35 TELETYPE SO THAT IS HOW THE REST OF THE MESSAGE GOT FININSHED In a message dated 10/20/2017 7:37:48 A.M. US Mountain Standard Time, jwest at classiccmp.org writes: Ed wrote... ------ HP 21mx/whatever processor works with double sided key... (I forgot model#) ------ Given the way you phrased it, the correct replacement for 'whatever' is M series. E and F never used the double sided key. However, even that is not entirely correct. Older M's used the double sided key. Later M's used the single sided key that is the same as the E and F. And.... ------- It has ... of all things 3 tty boards in it? what is with that? Multi user without a mux? ------- Didn't you sell and support these things in a prior life? It was always far more common to see the 21MX machines with 'discrete' tty boards rather than muxes. There were only two mux boards, the one in 2000/Access which was very uncommon as far as 21mx's go... and the one that RTE commonly used which was also not super common to find in the wild. If you had a mux board, then I would have been a bit surprised. Multiple tty boards? Not surprised, that was the far more common thing.... more often than not, the 21mx's weren't really used/targeted for multiuser (except 2000 TSB of course). RTE did multiuser well, but... still was probably most often used in situations that really didn't require it. Mux's weren't super common. And.... -------- Has 2 memory boards think I remember 64k total. -------- 64kb or 64kw? Remember, the M.E.M. option is required to support more than 32kw. On the M, MEM was optional. I believe it was standard on E & F. And... ------- need to find a paper tape basic to play with. ------- There are plenty of those floating around. Google is your friend... I think MU-BASIC may have been the one I heard people using? See below for a better option.... And... ------ Any other advice? ------ You should probably start by reading an introduction to the 21MX to get some basic background on the machines... Go to: http://www.hpmuseum.net/exhibit.php?hwdoc=108 You should start with 02108-90004 followed by 02108-90002 Finally - for you (and anyone else) that has just a cpu or a cpu and minimal peripherals, the best thing you can use to play with the machine is Terry Newtons HP-IPL/OS. See http://www.infionline.net/~wtnewton/oldcomp/hp2100/ and http://newton.freehostia.com/net/hpiplos.html Yes, you can run BASIC like you mention above. But it is a very well done "Forth-like" system that is well developed/flushedout. So in addition to BASIC, you get oh-so-many-wonderful-things. I very highly recommend that anyone messing with 21mx/1000 systems take a good look at HP-IPL/OS. Best, J