Robotron A5105 (Robotron BIC)

Every country had its educational computer. United Kingdom had its BBC Micro series, Poland had Elwro 800 Junior, and East Germany had this. Because KC85 computers became obsolete even for teaching IT, engineers from Measuring Devices Manufacturing Plant "Otto Schon" designed the A5105, sometimes called BIC (Bildungscomputer - training computer).
This system was far better than KC85. First, it has comfortable keyboard. It can be expanded with FDD or cartridges, and is much faster than KC. Graphics chip allows to get 16 colors, but in its version with FDD, monochrome monitor was supplied.
To run CP/M, a common operating system in 1980s, KC85 needed a special driver which in fact was another computer running CP/M. A5105 runs CP/M with its floppy disk drive, but CP/M is started from FDD controller's ROM memory. This makes much easier to use the system (no need to SYSGEN a floppy), but harder to modify it.
The computer was manufactured from mid-1989 to April 1990, about 5000 units have been manufactured. Most units were used in schools, but some leftovers have been sold under "ALBA PC" brand. Not much of these have been sold, as it was year 1990 and MS-DOS-based PCs became popular.
Technically, BIC has more western components than KC85 and instead of TTL chips it contains 2 large gate array chips (like ULA in ZX Spectrum). Picture is generated using D7220 graphics chip with 128kB of video memory, 2 times bigger than system RAM.

Manufacturer Robotron

Origin East Germany
Year of unit 1989
Year of introduction 1989
End of production 1990
Speed 3,75MHz
RAM 64kB,
128kB video RAM
ROM 48kB (Basic) + FDD ROM
Colors: 16
Sound: 3 voices
SCP (CP/M compatible)
Display modes: Text:
 - 25x40,
 - 25x80
 - 320x200x16,
 - 640x200x4.

Media: Tape recorder
5.25" floppy disk drive (780kB)

Power supply:

Built-in in floppy disk drive

OR external:

Looking to the rear of computer (male connector):

| 12345 |
| 6789A |

1,2,3,4 - +5V 1,2A
5 - +12V 0,1A
6,7,8,9 - GND
A - -12V 0,1A

  Joystick ports
Serial port for plotter and printer (V.24)
2 general purpose I/O ports
External FDD
System bus expansion
Cartridge connector
RGB output
Local network
Possible upgrades: ???
Software accessibility: Very Easy (CP/M programs)

My unit is in a vey good condition, probably it has never been opened. FDD works perfectly, so it hasn't been used much. It is a Robotron FDD, these FDDs had bad trend to fail mechanically (plastic hub displacing). In this unit it is good.


Contents: Starting Make floppy disks Pinouts Links


After pressing power switch on disk drive, unit beeps and displays start-up screen. This time FDD scans for floppy. If no SCP bootable floppy disk is found, system goes to BASIC.
If a bootable disk is found, which is detected by presence of SCPX5105.SYS file (even empty file), SCP operating system starts from FDD controller's ROM.
It still can autorun program from floppy:
 - If AUTOEXEC.BAS is present and no SCPX5105.SYS is found, contents of AUTOEXEC.BAS are loaded as Basic program and executed.
 - If AUTOEXEC.SUB is present along with SCPX5105.SYS, SCP executes lines from AUTOEXEC.SUB. This is a typical CP/M file submission routine, so it requires the disk not to be write-protected.
 - If AUTOEXEC.BAS and SCPX5105.SYS are present, the system loads SCP with error.

Make Floppy disks

To format a 800K floppy disk, you must have a 360K disk (some 1.2M may work). Start computer with BASIC, then type:

call format

Select drive A, insert floppy disk, Enter, J (Ja - confirm formatting) - it will format 160 (80*2) tracks. If bad sector is encountered, it will be noted.
Now let's make disk SCP-bootable by typing in BASIC:

save "scpx5105.sys"

Empty file will be saved.

To get files to/from PC, you can use two methods:

1. These disks are the same as Robotron PC1715, so method with 22DSK may work.

2. Go to This page and download DOS14CPM  package. This is a a 1.44MB bootdisk to just use Norton Commander (German version included).
This disk boots its own DOS and drivers which allow to access CP/M disks as normal floppy disks. This disk doesn't support FAT32 or NT filesystems so better use it in old computer. After booting, you have a 2MB RAM disk, PKZip/unzip, Norton Commander (German) and configuration program SELECT.EXE which allows to choose CP/M disk format. The last disk letter is usually a CP/M floppy filesystem.
I've successfully used this solution in controller in which previous method doesn't work. In general, use older PCs with ISA controller cards, they are more likely to work.





A/V RGB connector:

  131211109 8 7 6 5 4 3 2 1
| * * * * * * * * * * * * * | <--B
| * * * * * * * * * * * * * | <--A

1 - +5V DC
3 - Audio GND
4 - GND
5 - GND
6 - GND
7 - GND
8 - GND
9 - GND
10 - GND
11 - GND
12 - SYNC?
13 - NC
1 - Lightpen in
2 - Intensity
3 - Audio out
4 - Mono BSYNC
5 - Mono Video
6 - Blue
7 - Green
8 - Red
9 - SSP - SCART blanking signal
11 - SSV - SCART aspect ratio ??
12 - NC
13 - NC


1 - Output
2 - GND
3 - Input
4 - NC
5 - Motor ON

Joystick (form documentation: UNTESTED, my A5105 has different connectors):

1 - Left
2 - Right
3 - Down
4 - Up
5 - Fire 1
6 - Fire 2
7 - +5V
Ground in shield.

Plotter serial port:

Connector is the same as printer but FEMALE.

A1 - GND
A3 - CTS
A5 - DTR
B2 - TxD
B4 - RxD

Printer serial port:

A1 - GND
A3 - CtS
A5 - Shield GND
B2 - TxD
B4 - NC.

Video output:

1A - Intensity
2B - GND
4B - Shield
5A - Video signal.

Monitor power:

1 - GND,
2 - +12V DC
3 - Protective GND





Links (most are in German. You have been warned.): - Information, EPROMs and documentation of many Robotron computers. Go there to download CP/M programs for Robotron and documentation. - Downloadable software for A5105. - Description in RobotronTechnik site. - Emulator. Not tested.