Компьютер видеоигровой "Орель БК-08"
This "OREL BK-08" is a soviet clone of famous ZX Spectrum in very rare condition: it has been NEVER opened (factory sealed), never used, full original set, full description, original packaging, OTK (passed factory quality control) marking.
From a Google translation from the Russian
Original Site: http://witchcraft.org.ua/mnuspeccy/15-orelbk08
The central processor: UA880A (analog Z80A production GDR) or Z80A, with a frequency of 3.5 MHz. RAM 64 MB implemented in 8 chips KR565RU5V type.
RGB video output for connecting to a TV, the appropriate GOST 24838-47;
input / output for domestic cassette recorder, used as standard in long-term memory as a device;
two connectors for joysticks like Sinlcair / Kempston;
Connector bus system.
Address space CPU 0-3FFFH using software available registers can be displayed as a ROM, and on the addresses of RAM. The design fee includes the installation of two chipset ROM capacity of 16 KB each, but in practice only used one of them. Ability to select the source for a data read operation, while the recording is always done in RAM. This organization allows, on the one hand, to organize the loading of data into shadow RAM means BASIC-built system, but on the other hand, the contents of the shadow RAM may be affected by programs that do not take account of its presence. The data in the shadow RAM is not lost after a hard reset button RESET.
Keyboard BC - button, Reed, 67-key. Alphanumeric keypad zone coincides with the standard AT-keyboard set up the modifier keys. Pickup alphabetic keys - standard (QWERTY and QWERTY). Switching of layouts using special access keys RUS and P / A. Poll additional keys through the unused bits in the standard model keyboard port. The total number of software available keys - 56, other combinations of hardware emulates pressing Caps-Shift + and are designed to control the cursor and edit mode.
NMI processor can be initiated by the user by pressing the NMI, BC located on the body. This possibility, combined with the placement of the shadow RAM debug monitor is very useful in the development of programs in assembly language or machine code.
Other circuit design features
Wait states when accessing RAM available, which improves the system performance compared to the original ZX Spectrum or its clones such as the "Leningrad". RAM regeneration scheme does not depend on the contents of the register I processor, eliminating the known defect of the original model - the destruction of the image when recording in the register values 40H-7FH.
Accurate decoding of input-output ports (8 lines of address) favors the development of additional devices.
Request line INT automatically removed by signal interrupt confirmation, thus preventing problems with the duration of the query generation.
Number of clock cycles between interrupts is the same as the original ZX Spectrum - 69888.
Address signals to the keyboard output via K155LP9 buffers and not through the diodes, as on many other options ZX Spectrum. This will eliminate any interferences in the system bus from the keyboard.
Signals generated video controller running ROM (chip and K155RE3 K556RT4). Synchronization exactly matches the original ZX Spectrum.
BC is powered DC 24V (AC rectifier supplied). The body is placed BC pulse voltage generating primary supply voltage of +5 V and extra - +12 V. BC is not very sensitive to disturbance, occurring in the electric system, for example, when you turn on the refrigerator. The load capacity of the stabilizer on the +12 V is very small, but sufficient to supply the chip KR1818VG93, which was placed in the drive controller.
The package includes a set of basic BC Software: BASIC interpreter in ROM and a tape cassette with programs tst, MZ80 and RECLAMA.
Flash ROM contains the original version of the ROM ZX Spectrum, adapted to the advanced features of the IC. When loading the message "Basic System ver. 2.0."
Russification: the 7-bit encoding KOI-7 with a manual change output control codes. Modified ROM routines character input from the keyboard and display. Russian CG character tables are located in the upper address ROM, not involved in the original.
Implemented traditional ZX Spectrum input function words BASIC language press of a key, but the arrangement of the words on the keyboard is different from the original.
Handler NMI: instead of the default handler implements its activating shadow RAM, which causes an implicit transfer of control to code located in RAM.
Known errors corrected the original ROM were not. At the same time, the differences between BC architecture required to fix some other problems that were not apparent in the original architecture, but could cause partial corruption of data in the shadow RAM.
Small operating system designed for MZ80 run and debug programs in machine code and provides the following functions: control of the system input-output, load programs, launch programs, generate and copy the files (programs), debugging, service capabilities. 
The monitor is placed in the shadow RAM and activated by the user by pressing the NMI.
MZ80 opportunities as the debugger is not very diverse. For example, it lacks features such as disassembling the contents of memory or a step by step program execution.
Incorrect work with the contents of register R processor and features return to the interrupted program does not guarantee recovery after an NMI.
The program is designed to test the functioning of the main nodes BC: keyboard, control signal generator of color and brightness, sound generator, generator control signals color border, RAM and ROM, input and output signals of a cassette. 
Demo implemented on Laser BASIC.
BC provides only partial compatibility with the original. The main source of problems is the change in the contents of the top addresses of the ROM, which causes malfunction of programs (eg games Bomb Jack), using the ROM as the source address of an interrupt handler mode IM2.
The additional data
Here are the collected material from the set of deliverable computer:
Scanned principle and wiring diagrams (300dpi. Tiff and. Jpg);
Scanned manual (. Pdf);
Scanned Program Guide MZ80 (. Pdf);
Scanned guidance on the tst (. Pdf);
PC software, are available on cassette (. Tap).
The original description translated was:
Information about the item Description
Computer video game "Orel BC-08» ZX Spectrum-compatible personal computer. Domestic clone produced Dnieper machinehandel (Dnepropetrovsk, Ukraine).
-WTC telemonitora connector
--two connectors for connecting tape recorder (read & write)
--two connectors for the joystick type Manipulator (Sinclair and Kempston)
-the system connector.
Keyboard-gerkonovaâ, advanced, 67. Alphabetic keys – standard layouts (QWERTY and JCUKEN). Switching layouts are special service keys ENG and r/a. total number of program-accessible keys is 56. The remaining hardware emulating pressing the Caps Shift keyboard with numeric keys and are designed to control the cursor and edit mode.
Firmware ROM contains a version of the original ZX Spectrum ROM, adapted to advanced BC. When you download a message appears "the basic system of faith. 2.0 ".
Video signals are running ROM (K155RE3 and K556RT4 chips, synchronization corresponds exactly to the original ZX Spectrum).
There is a button, generating non-maskable interrupt. This feature, combined with the placement of the shadow RAM debug monitor may be useful when developing programmes.
Main technical characteristics
As the CPU uses BIS Z80A or its
Bits 8-bit microprocessor;
performance operations (type-register) per second-875000 ± 300;
capacity of RAM-65536 bytes;
ROM capacity-16384 bytes;
number of addressable pixels for display telemonitora-256h192;
the number of alphanumeric and special characters on the screen telemonitora-768 (24 rows of 32 characters per line);
number of colors on the screen at the same time, reproducible telemonitora-8;
number of brightness gradations-2;
the number of sound-1;
supply voltage-24V DC ± 20%;
Dise-power, not more 28 w.
Completeness of the lot
1. Computer video game "Orel BC-08".
2. power supply.
3. high-frequency Cable (for connecting the TV).
References of the computer include the following:
N 024706 XI 1994
It is complete with all the manuals (in Russian) and the original packaging which was unopened when it was received.
This exhibit has a reference ID of CH29848. Please quote this reference ID in any communication with the Centre for Computing History.
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