!11-PDP eht ni deppart m'I !pleH ================================ Today I have got a new toy: the Soviet pocket computer Elektronika MK-85M. I already have a bunch of Elektronika MK-85 ones (and a few MK-90s, too) but I never had the precious MK-85M. It is not very different, actually. The only change is larger RAM (6kB instead of 2kB of the MK-85). But these two extra chips made it not only more power hungry but also much expensive (RAM chips were expensive in the past). Thus it was also much less common. It was the first MK-85M which I ever spotted on the eBay (the MK-85s are quite common there). So what it this "Elektronika MK-85M"? It is a pocket computer which is designed to look and function like the Casio FX-700p calculator. It has the same dimensions, the same keys and its BASIC interpreter works almost exactly as the BASIC of that Casio. But... the Casio used some simple CPU. Soviet engineers (from the "Angstrem" company located near Moscow) used a CPU which was easily available for them. It was the 1801 series CPU [1]. These CPUs ware commonly used both in military and industry. These CPUs were Soviet designs (they are not clones) but they were compatible with the PDP-11 CPUs from DEC. Thus it is a device which looks like Casio calculator but internally is more close to DEC's minicomputers. The particular CPU used in these MK-85(M) has some limitations, it can address only small RAM (only 128 kB, I think but it was not so important because RAM size was mainly limited by available power source - and batteries in 1980s were much weaker than today's ones). So the MK-85 machines had only one 2 kB RAM chip and the MK-85M model has three these chips. The CPU can run in so-called "turbo" mode at 2 MHz but then the batteries can be flat in few hours. Thus it normally runs at something like 0.5 MHz. It is still faster than the CPU of the FX-700p (but some functions - namely the goniometric ones - in the BASIC interpreter are done in very ineffective way so actual computation is slower if they are used). There is also possibility to use external power source and then there is no problem with the "turbo" mode. It is interesting that it is sometimes stated that the MK-85(M) was produced from 1986 to early 2000s. Of course, in later 1990s it was produced only in small batches and often only on a special requests. For example, my machine has printed 1992 as a year of production but the serial number (which is pressed into the case, not printed) includes also production date which is 1995! (I assume that they used old cases with pre-printed date for a long time). The device has some advantages over the poor old Casio (FX-700p is from 1982, the MK-85 is from 1985). Some of the design and software mistakes were fixed (like the known exp() problem) and there is also added input and output in the Russian alphabet. Also, the 10-segment liquid crystal display can be used not only as alphanumeric one but every available pixel can be addressed individually. So some crude graphics is possible. There of course are some new bugs and - more importantly - the device pis much less durable than the Japan-made Casio. The screen protection pis from a low-quality plastic material but more important is lower quality of some connection between electronic components (the main problem is the display connection). It is interesting taht the keyboard is better on the Soviet model (it has better feedback and to me it seems to be more durable). And with so powerful PDP-11 in my pocket I can even play the Prince of Persia! Well, not exactly. There is a game written for the MK-85M which somewhat looks like the Prince of Persia but is of course much simpler (still, it only fits to large RAM of the MK-85M and it requires to run the CPU in the "turbo" mode). Now I have to find the link and re-type the game into the device. References: [1] gopher://gopherpedia.com/0/1801%20series%20CPU