ZX Nucleon 512KB is a new type of computer, respectively motherboard, software and largely hardware compatible with Pentagon 512KB from Russia. The motherboard is the same size as the ZX Spectrum 48KB Issue 3B, including important connector positions, and is therefore designed to fit into the original ZX Spectrum 48KB case or later replica box.

Pentagon, respectively Nucleon computers is the ZX Spectrum clones, but with some important differences. The main difference is that the Pentagon, respectively Nucleon does not know how to divide RAM into a slow and fast part, just like the original ZX Spectrum, all RAM is fast, The CPU is not stopped in any part of RAM. There is also a difference in timing, screen generation, interrupt generation, etc. Now these differences are calculated in a huge number of programs that arise from the 90s in the countries of the former Soviet Union, and that the vast majority do not work on the original ZX Spectrum correctly. This was the reason for the ZX Nucleon project.

Detailed information about Pentagon computers is available on the Internet and will not be discussed here.

Why buy ZX NUCLEON 512KB and not another, competitive project?:

The vast majority of the best quality software from the 199x-20xx period comes from the countries of the ex-USSR. This software largely uses Pentagon timing and does not work on ZX Spectrum and its derivatives. That's why ZX NUCLEON is the best choice for the future.


The ZX Nucleon 512KB is largely based on its model, the Russian Pentagon 512KB, which is somewhat 90% identical in terms of hardware. However, several improvements and changes have been made to the ZX Nucleon 512KB:

1. The computer does not include a Beta Disk floppy controller, both for spatial reasons and because Beta Disk is not so widespread in Europe, unlike Russia, and each user can externally connect the storage they prefer.

2. The computer includes an external I/O system connector that is largely compatible with the ZX Spectrum 48KB / 128KB (not +2A, +3).

3. The Z80 CPU bus signals are amplified by three-state drivers. This significantly increases reliability, especially with connected external devices. In rare cases, however, there may be incompatibilities with some devices that are not properly designed.

4. Increased reliability of the reset circuit by using inverters with Schmitt inputs.

5. Redesigned FLASH circuit, which is now generated using the exact frequency of the time base + divider circuit, not a poor quality and unstable RC oscillator, like the Pentagon.

6. Decoder of all ports (ULA, AY, paging registers) using CPLD GAL to simplify wiring.

7. The whole 512KB RAM is solved using one static memory + several LS-TTL chips around.

8. The switch can disable 512KB paging and put the computer in 128KB mode (due to incompatibility of some programs).

9. Completely redesigned part generating RGB and VIDEO signals through sum resistor matrix and PAL encoder + RGB driver. This part of the Pentagon was badly designed, with some circuits overloading.

10. Tape recorder input supplemented with quality amplifier.

11. Integrated audio interface AY-3-8910A, mixing channels switchable between ACB and ABC. BEEP and TAPE-IN and TAPE-OUT signals also added to the audio output.

12. Output video signals analog RGB and PAL S-VHS video + voltage 1V and 12V for switching TV are connected to Mini-DIN 8 connector. Voltage 12V is obtained on the board by the charge pump from the main 5V.

13. Switching regulator +5V/3A on board.

ZX Nucleon 512KB
ZX Nucleon 512KB
ZX Nucleon 512KB
ZX Nucleon 512KB
ZX Nucleon 512KB
     ZX Nucleon 512KB (Pentagon clone):