Linear Power Supply (Conversion Equipment Corp) from a basic four 510

Armin Diehl ad at
Sun Jul 19 16:43:32 CDT 2015

Yes, that is all correct. The first machines used by Basic Four (later 
MAI) were Microdata machines. Basic Four released BB1 (Business Basic 
Level 1) and BB2 on these machines. These were the “blue” ones, e.g.

Schematics for these are available at

Later they delivered BB3 and BB4 based on the 1300 series cpu that may 
have been developed by MAI (or are these “only” optimized Microdata 
designs ?). These are the “Orange” ones like this one:

I have scanned the schematics for the 1300 cpu, they are in the Service 
Manual System 200/410 starting on page 166:

I have two of these, one system 210 equipped with a 14” harddisk (Priam 
6650-30) and a system 510 equipped with 2 trident t80 drives.

Business Basic was their “operating system” on these machines. The basic 
had multi user and multi tasking capabilities as well as support for 
keyed, indexed sortfiles, ….

Later they ported this on the S10 (2x z80 cpu, one main and one video 
cpu). MAI bought the hardware design as well as the CP/M 2.2 
implementation on that machine. BBM (Business Basic Micro) could be 
booted from a copy protected floppy. This implementation had all the 
capabilities BB3 had (multiuser and multitasking worked as well). Later 
they added a harddisk to this system (is was originally equipped with 2 
80 track floppies)

The first machine they completely developed by themselves where the MAI 
2000, based on a 68010 cpu. They licensed Unos from Charles River Data 
Systems and implemented their business basic on this Unix compatible 
realtime system.

I have a working model 2000 and started to write a emulator for that 

Regarding the 1300 CPU, i would really know more about compatibility / 
similarity between the 1300 and the Microdata 1600. Both are 
microprogrammed and it may be (and I assume) that there are differences 
on the microcode level. May me the macrocode (correct ? I mean the level 
interpreted by the microcode) supports some similar code.

My eprommer can not read the 512x8 roms were the microcode is stored. I 
have already build a avr based reader on a breadboard to read out the 
proms but before removing the roms from the cpu board I want to have a 
backup of the readable part of the harddisk.

I have tried to boot the 210 beginning of this year, after a lot of 
retries the system booted to the basic prompt but while starting to 
write a dump program the machine hung and did not reboot.

Have to do more tests without the harddisk (but what can I do without 
the cpu documentation ?).

On 07/14/2015 09:46 AM, jwsmobile wrote:
> It is the follow on to the Microdata 1600 that Basic four used in its 
> first business machines.
> He has two machines and at least a disk for the system, I think.
> Basic Four became MAI.  They were noted for having a multi user basic 
> system for business very early on.
> Also it survive(s) today with a lot of installations in the 
> Hospitality industry.  Many of the fleabags you check into will have 
> MAI systems if they have terminal type systems.
> These systems were probably very near the 1600 hardware wise. They 
> appear to have the 130pin 1600 backplane connector.  I think Basic 
> four took slow steps away from Microdata's hardware, but eventually 
> progressed with all their own manufacturing, as well as moving on thru 
> bit slice designs, and eventually microprocessor based systems.  I had 
> a friend who worked there in the very early stages of their 68000 
> systems.  All while maintaining the Business Basic compatibility.
> It is quite interesting to see the photos of the boards, and I am 
> still studying them trying to figure out how much they changed in this 
> design.
> thanks
> Jim
> On 7/13/2015 9:22 PM, dwight wrote:
>> I'm not even sure what the machine is. Can you give
>> a little more information on what it is?
>> Dwight
>>> >Subject: Re: Linear Power Supply (Conversion Equipment Corp) from a 
>>> basic four 510
>>> >To:cctech at
>>> >From:ad at
>>> >Date: Mon, 13 Jul 2015 18:28:56 +0200
>>> >
>>> >Thanks, yes you are right. And it is fixed now. Would have been more
>>> >easy with the schematics on hand.
>>> >
>>> >But the 510 does not seem to start, may be the mini test program i 
>>> have
>>> >(to boot from terminal) only works with the model 210 and not with the
>>> >510. (
>>> >
>>> >Would really like to have the cpu documentation, than it may be 
>>> possible
>>> >to write some test code. (1300 CPU Technical Manual and/or M1300 
>>> Series
>>> >CPU Organisation and Description Reference Manual)
>>> >


Armin Diehl
ad at

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