This Polish computer was first introduced in fall 1983. As pretty much every
sophisticated piece of hardware from the Eastern Block, it was copied from
a western computer. The ROM is based on the TRS-80 model II, so the Meritum can be considered as a TRS-80 clone. It was mainly used in schools and is considered as the precursor of the polish computing industry as it was the first computer to be produced in Poland.
In fact the Meritum is not entirely Polish but rather a miracle of the eastern block industry : the keyboard and case is polish, disk-drives made in Hungary (some sources say Germany) and memory from Bulgary. 8'' disk-drives are said to be the Robotron K6500 ones...
The keyboard is quite special : left, right and down keys are situated on the right part of the keyboard whereas the up key is placed at the opposite left side !! Quite practical... Much weirder, two keys are blank !!
The Meritum has 64 graphic symbols. The Basic takes 12k of the 14k ROM. It is a Tandy Basic modified to use polish letters (Model 2). Some keyboards have Cyrillic letters for the Soviet union instead of the Latin alphabet. The system uses a U880D microprocessor which is a East-German clone of the Z80.
There are two models, the Meritum model 2 having more memory (48k RAM) and higher resolutions than the model 1. It can be connected to external disk-drives and have a built-in disk controller. It can use polish alphabetical signs and has a parallel port.
The Model 1 which had no graphical resolution (only semi-graphic symbols), no colors, small memory and very high price, was not very popular and was considered obsolete even before being marketed !
A Meritum III was released and shown on Poznan fair 1986, but apparently wasn't produced.
Among planned but never created accesories were: network interfaces ( this was actually produced for the II model ), and a expansion graphics processor that would in these days be called nothing more than a graphics accelerator :) Unfortunately, Mera was forced to suspend the productions of Meritums in favor to computer terminals etc. The whole assembly staff of the Meritum line was five people, and East Germany could not meet the demands for the 5,25" disk drives that were needed for the Meritum II. Meritum was abandoned, as it couldn't compete with private imports of C64 and Atari computers.
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About these countries, a small correction: 1. Floppy disk drives were Hungarian (very high fault rate) and later German. Theoretically they could be Bulgarian, as Bulgaria manufactured FDDs and disks these times. Eastern German 5.25" FDDs were mostly quite nicely working clones of Japanese Teacs. 2. Keyboard and case is Polish, as well as some chips made by Unitra CEMI and rarely TOMI. Keyboard is reed switch-based. 3. Many Meritum units have K565RU* memory chips, Soviet, not Bulgarian (has Bulgaria made memory chips these times?). 64K units may have Japanese/western chips as it was easier to get through bureaucracy and buy expensive western parts than to buy dense RAM from SU and slash yourself performing quality control again (Soviet export-grade chips had terrible quality control). Generally in silicon, chips in computers from Eastern block are East German (Z80-land VLSI chips), Polish (TTLs, rarely SRAM) or Soviet (all kinds), in some cases western/Japanese. Rarely Romanian (CMOS).
"A Meritum III was released and shown on Poznan fair 1986, but apparently wasn''t produced." - it''s not true. I have one. Elwro probably produced about 100 computers. I suppose still exist about 5-6 pcs.
Thursday 6th September 2012
I have this computer with improved ROMs - experimental serial interface based network management software is added and memory is expanded to 64K. Not always Bulgarian - sometimes there were Soviet. I heard about a few ROMs in this computer: First one, asks "MEMORY SIZE", it''s the first one. Next one, asks "OBSZAR PAO", it''s the most common one. My version asks "MEMORY SIZE" and displays "OETO-POL.SL.NET-BASIC" or something like that - it''s an experimental networking system, maybe one shown in technological exhibition in Bulgaria (?Plovdiv?). Network extensions are started by NET command. Another version tries to boot from floppy and if it''s impossible jumps to monitor. I don''t know anything about it except I have a photo of it running (from internet auction).
Saturday 24th September 2011
Model 1 : 1983 Model 2 : 1985
BUILT IN LANGUAGE
QWERTY full-stroke keyboard, 57 keys, arrow keys NMI, CTRL, SHIFT (x 2), ENTER, CLEAR, BREAK. Two keys are blank
U880D CPU (east-german Z80 clone)
Model 1 : 16 KB Model 2 : 48 KB (up to 64 KB)
32 chars x 16 rows
Model 1 : 64 / 32 x 16, 128 x 48 Model 2 : 64 / 32 x 16 (semigraphic mode), 256 x 192 (4 shades of grey), 512 x 192 (monochrome)
Model 1: monochrome Model 2: at least 4 colors
SIZE / WEIGHT
37.2 (W) x 23.8 (D) x 7.8 (H) cm
Power Supply (DIN5), Paralell interface (DB26), Serial Interface (DIN5), Tape-recorder (DIN5, 500 baud) Model 2 has an external disk drive connector (DB26)