AIM 65 Cassette Test Program

Mark Matlock mark at
Sat Jul 21 21:01:11 CDT 2018

   I’m not familiar with the program they mention for the AIM65, but in Section 9
of the User’s manual on bitsavers is a good description of how to set up cassette
recorders with the AIM65. If the recorder has a pause input the AIM65 can
control the tape both during read and write. If two cassette tapes were available
It could read assembly source code from one and write object to the other. (When
the computer came with 1K Ram expandable to 4K you did stuff like that.

On page 9-13 they do have two short test programs “SYN Write” and “SYN Read” 
that can be used to adjust record and playback volume as well as the VR1 pot
on the AIM.

If they are just looking for ways to save and load programs the best way was to utilize 
Teletype interface that is described on page 9-26. The described interface is for the
current loop that ASR33’s had but that is pretty easy to change to RS232 with some
external chips. With that interface 240 characters per second could be read or written.
If you upgraded the RAM a bit with an external board the AIM was quite a nice 6502 
development tool. I built a number of things with it.

1. Instrument to measure the stability of vegetable oils. (See “Oil Stability Index”)
This analytical method is still used today but with more modern systems. It used
a ICL7109 12 bit A/D, 16 relays, a pen plotter, and a home built conductivity circuit
with 32KB Ram with software burned to 2532 EPROMs. We wrote the source
on a PDP-11/24 and loaded it into the AIM65 for local assembly and store to RAM.
We used 2K Byte battery backed up RAM (MK48Z02B-25) on the AIM till debugged
then burned an EPROM.

2. A data acquisition system for a Perkin Elmer AA / Graphite Furnace.

3. A converter to change 66.67 baud 6 bit ticker tape code to 9600 baud ASCII.
(see <> ) Believe or not there was one
commodity exchange still transmitting their data in this format in the 1980s and
Our PDP-11/44’s DZ11 interface could do 50,75,110 and higher baud but could read
this data. This used a 6522 to generate 16 times the 66.67 baud and was fed to 
a UART to read it. 64 byte program, and 64 byte look-up table. 

4. A remote monitor that provided video output, and RS232 data recording from
9 digital temperature meters. The meters were read by counting their clock
pulses during the down slope of the dual slope meter allowing each meter
to be read with three wires (Ground, Clock, Gate) that were switched with 74150

So I have found memories of the AIM65 and the last time I had it set up about 2 
years ago it still ran fine.


Date: Sat, 21 Jul 2018 11:27:36 -0400
From: Bill Degnan <billdegnan at>
To: cctech <cctech at>
Subject: AIM 65 Cassette Test Program

Hi all...I got the following through my web site.  Does anyone have a good
known-working test program for an AIM 65 cassette that I can attempt and or
send in response?  I still have to set mine up and attempt to reproduce,
but someone here likely has more experience, it has been at least 5 years
since I powered mine on.  Also, the article this guy references from MICRO
April 1979 volume 11 is not present in my copy of MICRO, he may be mistaken
in his reference.  I don't know what cassette program he is referencing.  I
do know that the cassette test program that comes in the Rockwell AIM 65
manual is in error, but I don't have the corrections.  I also know that one
needs the correct (optional otherwise) power lines when using cassette.
Bill Inquiry -
I am one of the founders of the Computer Museum in Basel (CMBB/CMGB).
We have 2 AIM 65 units that seem functional. However, we're
experiencing problems with the cassette drive when trying to read back.
We tried to record using cassette recorders and also a modern PC
through line in and the audio signals are clearly recognizable
(from pin M). A connection to pin L and using the corrected program
to test readback from "micro_11_apr_1979_text_syn_read_program_AIM65.pdf"
only displays the "N" on either AIM 65 system. The cassette interface
potentiometers are sealed in one of the units by the manufacturer and
have never been changed as far as we can tell. Is there anything we
could try to get reading from tape to work? We are running our of
ideas. Is there any way to visualize the incoming signal through a
small program other than the one from the magazine?

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