LET'S (old topic)/and PDP-8I code/update - test-drb@ccmp.vtda.org

25 Nov 1999

-----Original Message-----
From: Christian Fandt &lt;cfandt(a)netsync.net&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Thursday, November 25, 1999 8:13 PM
Subject: Re: LET'S RESOLVE THIS ISSUE was (Re: Made a deal to get a
Vax6000,2Fujitsu Supercomputers and TOPS10???)

...
 Upon the date 06:11 PM 11/25/99 -0500, John B said
something like:

>>Some of us only see 1 or 2 interesting machines every year. And some of
>>us spend _months_ trying to track down an obscure option or manual for
>>our machines. And then we get people like this appearing...
>>
>
>You are not proactive ,.. sorry, that meant you actually have to financially
...
  commit to get
more minis! 
So, all of us who want to be proactive and save interesting machines will
become high rollers first :-/

no. just put out the money, time and space to house such units. We all know
that is not cheap. Fortunatly, I am able to fill a void and make some $$ in
the process.

and I wasn't refering to you., I know you have done some trips.

--------------------------------------------------------
now off that topic:

I got the 8I finally to lead a tape properly.. First a quick memory tester:

; 22 = FIRST ADDRESS TO START WRITING PATTERN TO
; 23 = CURRENT ADDRESS BEING WRITTEN TO.

    START
10    7200    CLA        ; CLEAR ACCUMULATOR
11    1022    TAD 22
12    3023    DCA 23    ; SET ADDRESS COUNTER
    MAIN
13    7064    LAS        ; LOAD ACC WITH SR CONTENTS
14    3423    DCAI 23    ; STORE PATTERN IN MEMORY
15    1423    TADI 23    ; LOAD WRITTEN DATA. (SHOUDL CAUSE A PARITY ERROR
HERE IS MEMORY BAD)
16    2023    ISZ 23    ; IF ADDRESS=0 , INC 23, SKIP NEXT INSTRUCTION TO
START LOOP OVER
17    5013    JMP 13    ; GOTO MAIN
20    7200    CLA
21    5011    JMP 11   ; GOTO START (RESTART)
22    0024    ; FIRST ADDRESS TO START WRITING PATTERN TO.
23    0            ; TEMP VAR, CURRENT ADDRESS TO WRITE PATTEN TO.

This routine will test all locations from 24->7777

Play with the SR and see if you can creat a pattern to cause the PDP-8 to
crap out. IF it does you know which location the problem occured at by
looking at the MA register.

The 8I ran this well.

I found out the problem was a bad solder joint on the paper tape reader
causing too much gain on certain holes.. (thereby causing bad reads at high
speed).

I am going to put up a bunch of little programs on my webpage so folks can
test devices without trying to get a paper tape up (will do TTY, and maybe
basic INST test, and some more core tests)

http://www.pdp8.com/

john

...
  --Chris
-- --