The Pentagon (Russian: Пентагон) home computer is an enhanced clone of the British-made Sinclair ZX Spectrum 128. It was manufactured by amateurs in the former Soviet Union, following freely distributable documentation. Its PCB was copied all over the ex-USSR between 1991-1996, making it a widespread ZX Spectrum clone. The name "Pentagon" derives from the shape of the original Pentagon 48 PCB which has a diagonal cut in one of the corners, giving it five sides.^[1]

• Pentagon 48K (1989 by Vladimir Drozdov)
• Pentagon 128K (1991)
• Pentagon 128K 2+ (1991 by ATM)
• Pentagon 128K 3+ (1993 by Solon)
• Pentagon 1024SL v1.x (2005 by Alex Zhabin)
• Pentagon-1024SL v2.x (2006 by Alex Zhabin)
• Pentagon ver.2.666 (2009 by Alex Zhabin)^[2]

The Pentagon 1024SL v2.3 included most of the upgrades of the standard Spectrum architecture, including 1024 KB RAM, Beta 128 Disk Interface and ZX-BUS slots (especially for IDE and General Sound cards). This model also featured a "turbo" mode (7 MHz instead of the original's 3.50 MHz).^[3]

• Russian most popular Spectrum models Archived 2012-07-16 at the Wayback Machine
• Pentagon 1024 official site (in Russian)
• Schematic diagram of the Pentagon 48K and drive controller (DjVu)
• 128K Schematic diagram of the Pentagon (the DjVu)
• Schematic and wiring diagrams Pentagon 128K 1991, revised and enlarged version (PNG)
• Wiring diagram 128K the Pentagon (the PNG)
• NEW English FaceBook Group