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

jwsmobile jws at
Sun Jul 19 19:59:17 CDT 2015

On 7/19/2015 2:43 PM, Armin Diehl wrote:
> 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 
> machine.
> 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.
The 1300 manual on the bitsavers site is nearly identical to the 
Microdata "great white" manual.  The CPU hardware is identical.

I saw a listing of the Microdata 1600 Basic four firmware and it is a 
modified and cleaned up version of the Microdata 1630 firmware.

The Microdata 1600 itself is a microprogramned system, and can emulate 
anything you want to take the time to write the code for the 1600 
microcode to emulate.  I have firmware to run 1130, Data General Nova 
and a number of other firmware sets.

It also ran the Reality firmware which is a totally unique virtual 
system.  Pick Systems extended the Intertechnique version of the 1600 to 
run an enhanced Pick system, and Microdata extended the design to also 
expand the performance and make another 1600 based cpu to run their 
Reality system.  The Reality system is of course the Pick system as well.

The unmodified as designed 1600 supports 64k of core, and that is what 
the Basic four had for memory.  They implemented a macro code which 
resembled the 1630 code, but had some of the really bad design decisions 
fixed.  The main problem with a multiuser system using teh 1630 is that 
the subroutine calls placed the return address at the address referenced 
in the instruction, and began execution at the first byte beyond that.  
That made multiprogramming very messy since the return addresses were 
actually in the code being executed.

The basic four instructions also had a sense of executing code from 
either the first 32k of memory, in a privileged mode, and in the last 
32k in a user mode.  I didn't see the OS to know how that actually 
worked.  But there were comments in the code indicating that the last 
32k could be swapped.

> 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)
>>>> >

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