Disorganised, but interesting. Russian COmputers...

As some of you may know, I'm mad-keen on Russian calculators and computers - see my site Museum of Soviet Calculators at http://www.comcen.com.au/~adavie/slide/calculator/soviet.html Although I dropped off this list some time ago, and remain off, I thought I'd write and give a "brief" summary of information to hand. The data here comes from my many Russian "agents", and mostly is the first time that any of this has been presented in the West. It's long, some is missing, but it's really fascinating, no? PLEASE DO NOT POST THIS DATA ON YOUR WEB PAGES. It is my intention to build a site on Soviet computers - to complement my calculator site - and I would be reluctant to ever again share information if the rug is pulled from under me! After all, it takes a lot of time and effort to dig up information. Copying it is easy. I do welcome feedback/questions on this info - I can pass on specific requests to my sources. Before presenting the data, a brief plug - I have two handheld Russian programmable calculators for sale - the MK-85 and MK-85M (both viewable on my site). Please contact me privately, at adavie(a)mad.scientist.com if you're interested in purchase. Cheers A And now, for the interesting (disorganised) stuff... mostly unedited ------------------ 13.05.99 in our collection Sinclair-compatible of computers one more copy has appeared. Externally it looks so: the system block of weight 6,8 kg with the remote keyboard! It was assembled by the radioamateur in 1993. All local boys played on this computer. I expected, that its appearance will be more aesthetic and beautiful, namely: the keyboard and motherboard in one case with the remote disk drive of 5 inches and separately power unit on 12V and 5V. And there was, that almost all in one box and rather heavy because of a power unit and using of metal for the plating of the case. Besides the buttons on the keyboard are not closed by the decorative panel, there are no labels on 2 buttons, and the system block will not sustain a long road because of bad fastening... But, most important, that all this design works! The machine is connected to a socket SCART of the TV set. And most interesting is made in disk operational system. It refers to as DISK SERVICE. It is very simple in work and is intended only for game use, though probably partial use and for the decision of practical tasks. In a basis of system nonfile architecture, and blocks lays. DISK SERVICE divides a flexible disk into 16 blocks. One game or condition RAM can be stored only in each block which existed in the computer at the moment of pressing the button NMI. Naturally, it is possible to save and to load game, and also to read of directories of a disk! At the moment of recording of game on a disk the machine requests a name of the program and writing it on a disk. At reception a directory the computer looks through each block and gives out the list of games. Due to an opportunity of reception of the list of games (the directory of a disk) DISK SERVICE is better, than DISK MO! NITOR. Besides DISK SERVICE faster loads and reads blocks. On all other parameters it considerably concedes DISK MONITOR, because last has opportunities of the built - in toolkit and debuggings of the programs. Thus in our Russian gallery of microcomputers there are following computers: 1). "Leningrad-1" without the disk drive (is ready to travel to Sydney) 2). "Baltic" with the disk drive and operational system DISK MONITOR (I prepare to sending. I do not like its heavy power unit and unreliability at work with the disk drive - I removing now). 3). "Baltic" with the disk drive and operational system DISK SERVICE. To me has got to it about 49 disks with the information in a format DISK SERVICE. Probably, I should it result in more pleasant condition, to reduce of weight and other. Or to leave all in an initial condition. What do you think in this occasion? 4). Byte without the disk drive. Was let out in Belarus. While I have faulty copy, but, now I undertake efforts on its repair or search of working model. 5). "Anqstrem". In a basis - 13 microcircuits. Somewhere at home at my parents the system board lays. When I shall hold it in hands, ladies acknowledgement(confirmation). But to this payment are necessary still keyboard, case and power unit. And only then it will be the working computer. Besides this payment can be and faulty. What you think in this occasion? When I shall hold her(it) in hands, I shall inform acknowledgement. But to this board are necessary still keyboard, case and power unit. And only then it will be the working computer. Besides this board can be and faulty. What do you think in this occasion? 4. One boy offers me the microcomputer under the name "SPECTR-001". I while think. What this such? It is constructed on the basis of the Soviet 8-digital processor KP580BM80 (western analogue, if not changes to me memory, i8080). 32 kilobytes of the RAM, 2 kilobytes of the RAM. It Is assembled on the basis of the circuit of the microcomputer RADIO RK86 and programs compose to it. RADIO RK86 was developed by the Soviet radioamateurs. Its circuit was published in a magazine "RADIO", released on all territory of the USSR and all radioamateurs could quietly collect the computer on the basis of the publications and recommendations in this magazine. Thus, it was one of the first Soviet official computers assembled on domestic element base. Except for it was still MIKROSHA (circuit was published in a magazine "RADIO") and SPECIALIST (the circuit was published in a magazine "MODELIST-CONSTRUCTOR"). Then has appeared ORION with an opportunity of connection of the disk drive and other m! odels. Approximately in this the Soviet people have opened for self the ZX-SPECTRUM and have made the final choice for the benefit of it... And in the beginning there was a magazine "RADIO" with the circuit RADIO RK86 (86, probably, name of year of the publication of the circuit). Then this circuit began to be realized by an industry with small completions under other commercial names. One of them - "SPECTR-001". ------------- I continue translation of the article " BK - supercomputer " (part 2). " The Greatest damage for BK is put by amateur perfomance of half-competent enthusiasts - rationalizers. And already it is complex to result all park of these machines in the coordinated condition so that all available self-made devices have not turned to monuments of the vainly spent means and health. Nevertheless, we shall try.. WISHING to write the programs for BK - more than it is enough. ABLE it to make too burn by desire to apply the knowledge and skills on more wishing "hard". The enthusiasts already have included the tools and the circuits it long of desired "hard" wait.. So, what the processor 1801BM1 can? If to address to the directories and operation manuals, it is possible to find out the rather interesting items of information: "... The processor 16-bit... Address space 32 K ". And it, perhaps, most unintelligible for amateurs. Because in any textbook on circuitry it is possible to find the formula, from which follows, that 16 categories are 64 K of various addresses... The business here that with the help 16 bit of the bus of the address the processor addresses both to 16 bit of the data, and to the senior half of same data. Therefore 16 bit data (words) have only even addresses (or only half from 64 K possible), and the odd addresses allow the processor to address only to 8 - bit data (senior half of word of the data, or to senior byte). The reference to bytes is necessary for the processor to work with the texts, which symbols are coded in the KOI 7 and 8- bit data. Therefore in the processor one more additional line (17-th) address is stipulated, which allows to address and to younger byte of the data. This line refers to as WTBT (pin 40). That is, actually, the processor 1801BM1 has the 17-bit bus of the address, but two bits of this bus (0 bit of the bus of the address and WTBT) carry out actions essentially distinguished from actions of other 15 bits (1... 15 bit of the address), and we have an opportunity of the reference to 32 K of words of the 16-bit data, and on bytes - and to 64 K of 8-bit words (bytes) The basic mode of the processor: the work with the 16-bit data, therefore processor changes on the bus of the address only meanings in bits 1... 15, and the changes on a line WTBT and in the zero bite of the address occur only with detection in the program or special teams of work to bytes (younger), or with the requirement of the program to address to the odd address (that is to senior byte). It - basic features of the processor 1801BM1, which frequently serve for amateurs familiar on a magazine of "Radio" with the 8-bit processor 580 BM80, source of all misunderstanding. There is at the processor 1801BM1 one more interesting feature: it works with the general (common) bus. That is both address, and the data are transferred by the processor to other microcircuits on the same lines... And I are distinguished signals of the address from signals given only by that first in addition are accompanied by a signal of synchronization SYNC (SYNCronization, pin 41), while last - signals DIN (Data IN - data input,) or DOUT (Data OUT - conclusion of the data, pin 37) and, if necessary, signal WTBT. By anything other these signals from each other do not differ! And if we shall find a method, which will allow some data too to count as the address, the bus of the address is increased by 16 bits! (Repeated procedure - more for 16... Etc.). Thus we shall have an opportunity to be addressed to 231 16-bit words and to 232 bytes or to work from the RAM of volume 2 Gigabytes!!! (Here even by a bag RU7 will not do without!!!) Certainly, such of "gigabytion" for a amateurv, and majority of the professionals-homers is absolute by anything. Therefore to expand the bus of the address on 16 bits shall not be. If to be satisfied by expansion of the bus of the address on 8 additional bits, it will give us an opportunity to address 4 Mbytes. When the processor run out the program, it is consecutive (with absence of branchings) gives out numbers of addresses, since 0 (or from any other = to the address of a beginning of the program). If nothing will prevent, it will reach the latest address 177777, and it will leave on 0 and further will return to that address, from which began. That is the processor will bypass complete "CIRCLE" of addresses. For example, the processor 1810BM86 cannot itself (without the special program) to bypass a complete circle 1 Mb of addressed memory - for it it is same 64 Kb, as for the processor 1801. The part of such address circle by analogy to a geometrical circle usually refers to as as a SEGMENT. However, in the processor BM1 such segment addressation is not stipulated (though there are special microcircuits, controllers, the arbitrators etc., but this exotic is accessible a little). Nevertheless, to organize "artificial" (hardware-software) segmentation for 1801BM1 does not represent any difficulties. As it, as it is strange, is stipulated by the electrical circuit BK-0010! (It is interesting, where that disappeared so provident " the developer ", if instead of expansion the issue BK-0011 is begun composed with 0010 only on a network cord!? The bus of the BK-0010 address is hardware is already divided on 8 segments on 8 Kb or on 4K of addresses in each. Two younger segments occupies the RAM of the user (to which more all claims by critics). Two following are occupied by the screen. And in stayed four the microcircuits of ROM are placed, from which two are least spoiled by rationalizers only: the MONITOR and TEST DIAGNOSTICS (block MCTD). Fortunately for the owners BK-0010, it is possible to neutralize "fruits of rationalization" through a socket of a system bus XT3, and here the owners "advanced" BK-0010.01 was not lucky, they should open the machine to cut the pathes going to the out CE (pin 23) microcircuits of the ROM of a BASIC (of the microcircuit D818 and D819) and to establish a connection from released pins to a pin 23 microcircuits D820, which switching-off the rationalizers were compelled to leave, MCTD differently would not work. (The One who instead of sockets under the ROM in BK-0010 already rigidly has established a BASIC, it is necessary to repeat the described procedure. It is enough to them to take out the ROM from the socket). Though, if yours of BK on a guarantee or you it would not be necessary to enter the conflict " with a rationalization idea ", it is possible anything it to not do. The system "BK+" will work! Only operational system will determine absence of program management in the appropriate segment and independently "will cut down" some and your opportunities." To be continued.. My wife does not support my enthusiasmes for microcalculators and microcomputers. She forces me, that I held outside of an apartment and any stuff "did not collect". She asks, what for to me any old small computers, when I have one present. Andrew! Sometime she will finish me up to temperature of boiling, I shall become angry and I shall throw out either calculators or wife!: -). She should understand, that I and mine calculators is one and too! Love me - love also my calculators.. For now I should work confidentially.. ------------- I continue the translation of the article " BK - supercomputer " (part 3). "Now, if you were reserved in ten microcircuits of any triggers, counters, multiplexers and logic, and to them have 16 cases of memory of any type, it is possible to begin! The whole design will be connected to a socket of a system bus, therefore, certainly, the socket CH063-64/95-24-2 is necessary which enters into a complete set of delivery BK (if you already used it for connection of the printer, it is possible completely dismantle the block MCTD, and microcircuit from it to mount " by the second floor " direct on anyone of ROM of the basic scheme, to bend pins 23 and by establishing the additional switch, as on the circuit given in a magazine " Informatics and training " (90/4, page 72). By the way, to pull cable, as there it is recommended, there is no necessity...) It is best to use microcircuits of series 1533, 555, 176 and 561. With presence of microcircuits only 155 series should be found two bus shapers of a type 1533AP6 (555AP6) or series 580 to not overload the bus A/D. (All system managing signals it is necessary "buffered", for example, by microcircuits 1533LN1, 555LN1 or any logic). Pins of a socket XT3 for A/D00... A/D15 accordingly: A31, B31, B29, B30, B28, A28, B27, B32, B26, A27, B25, A26, B24, A25, B23, B7. On these lines it is necessary to establish Latch of the address. For it it is possible to use two cases IR22, IR23, IR27 (it is possible two cases TM9 and one of TM8 and so on). The address latches a system signal SYNC (pin B22 XT3). It switches off the third condition on an output of the registers of latch of the address. ( If in latch TM8-9 is used, they are reset by a system signal RESET with inclusion BK). The latch of the address is necessary to fix segment, to which the processor addresses to generate all necessary signals and their sequences for interaction of the processor with expansion and for organization of "internal" work of the Expansion. As in BK is hardware there are 8 segments, which to us need to be operated programmly, for it it is necessary to use three hi of the digits of the address: A13, A14 and A15 (other digits operate expansion within the limits of a segment). Segments with RAM of the user and screen is better for not touching. A segment with ROM of the monitor too... It is necessary to remember, that without the monitor BK turns in "well-to-do'hard only"!.. But this segment is used in half of opportunities - only for reading. It is irrational. The ROM 1801PE2 microcircuits are arranged in such a manner that when there is a reference of the processor in their segment and thus the signal of reading (DIN) is active, the microcircuit gives out the data on the bus, and then and signal for the processor RPLY (RePLY - response). With absence of a signal DIN the microcircuit does not react to the address of the segment, and with absence of a signal RPLY the reaction of the processor is rigidly determined: it counts 64 steps of the synchro-generator and works further under the special program of a MISTAKE of the REFERENCE or LAG. That is the segment ROM of the MONITOR is completely free for record: ROM in any way and nothing prevents and cannot be as - or "is spoiled" by signals on the common bus. Therefore we shall establish in this segment one more latch - latch of the data, which will serve (programmly) a command word of "artificial" segmentation or WORD of MANAGEMENT of other segments for their use, similarly to a segment of the monitor, - both for reading, and for record. This latch is similar to latch of the address and differs only by that the signal for latching is formed of a signal of decoding of the reference on record in a segment of the monitor, that is with presence of levels 100 on the hi bits of latch of the address and active level of a signal DOUT (pin B21 of a socket XT3). Then (not later, than for 60 steps of the synchro-generator) the circuit of management should give out a signal RPLY on pin B20 of a socket XT3, differently processor lags." To be continued... ------------- I continue the translation of the article " BK - supercomputer " (part 4). " For what the 16-digit latch of a word is necessary, if we already have agreed to use expansion of the address only on 8 categories? Business that it is meaningful to use the following behind the monitor two segments each separately. And data you see all the same 16-digit. Therefore younger byte of the data we shall use for management of the segment, nearest to the monitor, and senior byte - for management of the following segment. (The latest segment 111 is better by anything, except the ROM MSTD or BASIC to not occupy, as in these microcircuits the automatic blocking is stipulated in the field of addresses of the system registers 177600... 177777 - Any amateur perfomance here, as is spoken, is fraught...). The segments 101 and 110 form two SEGMENTS of ACCESS to the expansion controlled by the processor with the help of the address, which has stayed 13 lines, and system signals. Each of bytes of a word of management allows to include in each of segments of access any of 256 (2 in a degree 8-256) 8 Kb of segments of expansion. (As against the processor 1810BM86, here segments of access are not blocked in any way, therefore transfer of the data from one part of the program in other should be carried out differently). If each of segments of access will use own bank, we shall receive expansion of volume in 4Mb (8K x 256 segments x 2 banks - 4Mb), but if to be satisfied by one bank for both segments of access, we, losing half of volume, receive an opportunity any 8 Kb by blocks of this bank, that is much more attractive, as and 2 Mbytes to fill by any useful data with "poor" periphery are not obviously possible, and hardly it is required to somebody for the "home" purposes. Now we shall look, what we can insert into this of 2Mb bank?.. Even having 16 pieces 565RU7, we use only quarter of volume of this bank. But it is a rather interesting quarter! It makes equally 2 digits words of management. That is, if bank to choose by these quarters, we shall have in bank four SEGMENTS of CHOOSING on 512Kb each. And in each of them we can arbitrary choose blocks on 8Kb or WINDOW. The choice of windows will be carried out with the help of the 6 bits of each byte of a word of management for each of segments of access in any segment of choosing. Where it is necessary to insert these two bits of management of segments of choosing? They should be placed in most younger and in the grown-up bits of each byte of a word of management. Such accommodation will be well coordinated with logic of work of the counter of commands, i.e. with its use for scanning of data in the next windows will not occur switching of segments of choosing. And use for the same purposes of other register will allow to carry out scanning with switching of segments of choosing or without it, depending on desire of the programmer. It is necessary to distribute duties between these segments. " ( To be continued...) I offer to your attention the survey article on some computers of family Sinclair collected in USSR. Review included the basic, most popular models. However, some models, for example, is industrial made, in the review are absent. The facts touching my favourite computer Baltic partially are deformed. On Baltic it is possible to start 3 (!) Operational systems - standard Basic, built - in original Disk Monitor and from disk to load CPM! Besides it is rather easy to connect to it any periphery, though it and does not have the allocated system trunk. Thus, it is interesting, though also rather disputable article. Here it is necessary to remember, that the article is written by the inhabitant of Moscow region. Since 1987, at shop "Pioneer", then on Sokol, in Pokrovsko-Streshnya and still god knows, where in Moscow, and now at station of the underground "Tushinskaya" has appeared about ten basic models Spectrum-compatible PC (personal computers). These models and their various versions make now by basic park household PC in former USSR, due to their simplicity, cheapness and huge quantity of the excellent programs. To a radioamateur, and at times and professional, it is difficult to understand advantages of one models before others, as practically there is no information on subtleties both complexities in setup and operation, and also compatibility with the software. The problem also is, that nowadays, the selling of some models PC has appeared in a circle of interests of their developers. As a rule, the information on such of PC - is advertising, and the shadows parties are not shined. The first mass model has become PC "Moscow". This of PC till now remains by the most high-grade recurrence of model "ZX Spectrum" from the point of view of machine cycles and organization of memory (however it complex in manufacturing and setup, and also requires large number of completions, which are necessary for bringing in). It is necessary also to note, that in the television frame at "Moscow" 312 lines, that corresponds to the standard, instead of 320, as at the majority of other models. Only in this model braking the processor is stipulated with a video-out and reference in addresses with 4000H up to 8000H (16384 - 32767 decimal). However complexities in set-up do PC "Moscow" not enough attractive for beginning radioamateurs. The following step PC was "Baltic" (name has taken place because, that printed-circuit-board and circuit have developed in Vilnius). The basic advantage of this model is the simplicity and high safety in operation. On a printed-circuit-board there are few of corrections, and the computer is simple in adjustment. But the presence of microcircuits K556RT4 and K155RE3 necessary for organization of machine cycles and work of the videoprocessor, which are necessary previously for programming, imposes some restrictions on availability. The rigid organization of machine cycles and essential differences in organization of work of memory, and also increased thereof up to 4 MHz clock frequency of the processor, makes this model less compatible programmly. For these reasons nowadays "Baltic" is distributed a little. By essential step was the occurrence of model " Moscow 128 " (developed, most likely not in Moscow). It is the first model, where is used "transparent" RAM, i.e. the mode, in which processor with the reference to memory is not braked. As the prototype of this model PC " Sinclair 128 " has served. But use of memory in critical modes, and also the absence musical co-processor has made this model by rather poor recurrence. The interface of the printer LX-print and original programmed joystick were stipulated in "Moscow 128" for the first time , connection two of Kempston-joysticks and high-grade TV-RGB an output also is stipulated. Unfortunately, this model has not received distribution because of small quantity of the programs designed only under "Sinclair 128", and complexities in setup shown, as "Failure in RAM". Most mass model Spectrum-compatible PC without the controller of the disk drive has become " Leningrad I ". Its basic advantages: simplicity, cheapness, small quantity of corrections on a printed-circuit-board, repeatability. Because of absence of the worthy competitors this model has got large popularity. Unfortunately, it was necessary to pay for simplicity by bad compatibility. A wrong choice of addresses of ports, and as a consequence - By-effects and complexity of connection of external devices. On a printed-circuit-board the system socket is not stipulated, and to connect any periphery very difficultly. Though the braking of the processor in a cycle Ml (with choosing of a code of the instruction of the RAM) also facilitates mode of operations of memory, but strongly harms to compatibility with the software. Nowadays this model gradually descends from the market, though also its followers are not deprived of many mistakes, admitted in it. the computer "Pentagon" or " Pentagon 48 ", nicknamed so for five-coal distributing of the earthen trunk on a contour of the printed-circuit-board. It was first model Spectrum-compatible PC, in which on one printed-circuit-board the computer and controller of the disk drive is located. "Pentagon" has borrowed from " of Moscow 128 ", in particular transparent RAM, addressing of ports, and lacks peculiar to "Moscow 128 " much. The dynamic memory in this model works on limiting frequencies, and the printed-circuit-board is divorced by the not best image, because of what it is necessary to strengthen bus of a power. n a printed-circuit-board there is no circuit of formation TV-RGB of a signal, and it should be done device of input from the tape recorder (on K561LN2), and as negative - absence of a system socket. "Pentagon 48 " is popular also now, though the machine with 128 kilobytes RAM is gradually superseded similar. Hardly later "Pentagon" in the market there was PC "Krasnogorsk". Is original model, in which for formation of television signals ROM K573RF2 (5) with the table programmed in it is used. In "Krasnogorsk" is used, though also transparent, but the mode, facilitated at the expense of a rigid machine cycle, of the RAM, on a printed-circuit-board is divorced the shaper TV-RGB of signals. This version PC has become attempt to correct lacks "Baltic" and " of Leningrad I ", but because of difficulty of purchase ROM with the table, complexity of expansion, because of absence of a system socket and wrong addressing of ports this model has not become same mass, as " Leningrad I ". Nowadays "Krasnogorsk" is distributed in the market very little. After occurrence in the beginning of 1990 "Krasnogorsk", by virtue of a number of the reasons, in the market household PC more than year did not occur of new models Spectrum-compatible of computers. The occurrence PC " Orion 128 " on the basis of the processor KR580IK80, with anything not compatible programmly, has not rendered essential influence on development household PC. However spring and summer 1991 in the market has appeared at once some new models. " Leningrad 2 " represents of improvements variant " of Leningrad I ", in comparison with it in new model is corrected addressingt Kempston-joysticks, though have remained mistakes of addressing "border" of a port FE (254). The videoprocessor forms 312 lines in the frame, the external bus is outside . " Leningrad 2 " is much better than the predecessor, but, on all visibility, same popular it has not become. One of the reasons it is the complexity of expansion, as well as at all previous PC, absence of controllers developed under specific model. The computer "ZX-PROFI" the first of developed at us of PC, in which besides a mode 48 and 128, is stipulated also use of operational system ???. The computer consists of two printed-circuit-board and is combined in enough to setup, but has the most complete set of periphery in one block. The authors and distributors will carry out correct market politics directed on a wide circulation to this model. But their mistake is that complex and expensive half-professional PC is not necessary to basic mass of the potential consumers. Advantage of this model is the mode "TURBO", and lack - Incomplete compatibility both with ZX Spectrum, and with ??? PC ROBOTRON 1715. In comparison with "ZX-PROFI" " Pentagon 128 " has appeared more simple and mass PC, though, as a matter of fact, it only crossing " of Moscow 128 " and "Pentagon48" without essential improvement. The machine is difficult in set-up, is critical to RAM, on a printed-circuit-board there is no place under musical co-processor AY-8912, but nowadays this computer, unfortunately, unique. "ATM-turbo" - Is pure commercial PC. The politics of its authors or manufacturers focused on protection of "copyrights", most likely, is directed on reception of the maximal profit to short terms. This, undoubtedly, original PC is most expensive also complex nowadays. In it some grafics modes (only in ???) are stipulated, but, unfortunately, these additions - presence analogue - digital converter, digital-to-analog converter and elements for the modem and automatic determinant of a telephone number on one printed-circuit-board, - Nowadays are not maintained in any way programmly. In the computer there is no sufficient flexibility and even of a system socket. Similar, the problems of compatibility with ZX Spectrum of the developers interested a little, and "???" it is possible to consider as ??? - compatible PC. On the present time last model is "Angstrem", in it a microcircuit 1515XM1 for the first time is applied. It is a set of counters, multiplexers and fine logic. Simplicity in manufacturing and cheapness, undoubtedly, will make in a near future this model popular. But essential step in it was only technological simplification with use 1515XM instead of a set of separate microcircuits. Among advantages it of PC - simplicity in setup, and among lacks small flexibility, in particular, impossibility of expansion of the RAM and deficiency 1515XM1. And what is farther? The information on quick occurrence new PC with two processors Z80 recently is received. From words of the authors, in it all problems of compatibility, and opportunity of expansion are solved, as almost. The printed-circuit-board in this model is similar on structure on Matherboard IBM PC, i.e. with several system sockets. It would be necessary to trust, that too not advertising. And it is desirable to the developers new PC to provide: availability, small set of elements, reliability, openness of architecture (ease of expansion), and from the point of view of compatibility - Correct addressing of ports, presence on a printed-circuit-board so-called " f a port FF ", correct situation and duration of a signal INT (inquiry of interruption). Well, and the one who does not want to wait (and whether will wait) occurrence "ideal" PC, it is possible to choose model on taste and pocket. Is desirable to you of good luck! " --------------- In 1982, the Englishman Clive Sinclaier has invented the 8-digit computer ZX-Spectrum, which was connected to the TV set and had the programming language Basic. Soon for it he has awarded a honourable rank sir, and in USSR this computer has become mass national computer and radioamateurs, which already have ceased to arrange programmed calculators: -), have begun to copy the electrical circuit ZX on soviet element base. The first popular circuit in 1986-1994 (time their greatest occurrences) was Leningrad. It was the simple circuit with the least quantity details and for the first time was thought up in Leningrad. Whence and name. In Minsk have begun to let out by an industrial image a Vector and Byte, ZX-Spectrum compatible too. There were more competently thought over models ZX - later Scorpion (it seems, Moscow) and Baltic (is developed in Tallin and distribution has received in Minsk). These circuits differed safety in operation, opportunity of connection of peripheral devices, including the disk drive. I personally itself have collected a little Baltik of computers and has set up them. At me till now is working Baltic with the disk drive. I know three operational systems for Baltic, including TR-DOS. There were also other clones ZX-Spectrum. As to 16-digit home computers, the soviet designers have let out BK-0010 with the programming language Focal and on the film keyboard. There were perfect updatings with Basic and contact keyboard later. Then I have learned, that BK-0010 and its clones were are copied from western model. For this reason it of all opportunities has not opened. :-( . Itself programmed on it and even modernized the circuit. But the epoch of ZX-Spectrum and BK-0010 irrevocably has passed. By it on change came IBM-PC-compartible. ------------------