A modern, through-hole friendly reimplementation of the classic Pentagon architecture — designed for reliability, expandability, and ease of assembly.
- ULA implemented using Altera CPLD (EPM3256)
- 512 KB RAM
- 128 KB ROM
- Built-in DivMMC
- Z-Controller support
- YM2149F TurboSound (true stereo output)
- Kempston-compatible joystick interface
- Bluetooth audio module for game loading
- WiFi Ready
- RGB (Mini-DIN/9, Sega-style)
- Composite
- S-Video
- EAR / MIC (tape interface)
- Line audio output
- Input supports either polarity (protected)
- Fully optimized for through-hole assembly
- Ideal for DIY and retro enthusiasts
| Mode | Description |
|---|---|
| 🟦 Universal | Pentagon 128 KB + DivMMC / GLUK Service + Z-Controller + TR-DOS Ramdisk |
| 🟥 C | Experimental ZX Spectrum +3 with MMC and +3e ROM |
The CPLD firmware in the universal version was developed by Andy Karpov. Thank you.
- Rev 1.0
Initial revision.
-
Rev 1.1
Added the ability to disable the built-in TurboSound for compatibility with external audio interfaces (middle switch). -
Rev 1.0
Initial revision of ZX Spectrum +3 mode.
| Bank | Address Range | Content |
|---|---|---|
| 0 | 00000h – 03FFFh | GLUK |
| 1 | 04000h – 07FFFh | TR-DOS |
| 2 | 08000h – 0BFFFh | BASIC 128-P |
| 3 | 0C000h – 0FFFFh | BASIC 48-P |
| 4 | 10000h – 13FFFh | esxDOS 0.8.9 |
| 5 | 14000h – 17FFFh | DiagROM |
| 6 | 18000h – 1BFFFh | BASIC 128 |
| 7 | 1C000h – 1FFFFh | BASIC 48 |
| Pins | Mode | Usage |
|---|---|---|
| 1–2 | Composite Sync | Use with Mini-DIN/9 → Composite cable |
| 2–3 | RGB Sync (CSYNC) | Use with Mini-DIN/9 → SCART (Euro RGB) cable |
👉 Tip:
- Wrong setting = unstable or no picture
- SCART users should almost always use 2–3
| Mode | 1 | 2 | 3 |
|---|---|---|---|
| 🟦 Universal | Switch between DivMMC / GLUK | Diagnostic ROM | DivMMC ON/OFF |
| 🟥 C | Switch between +3e / +3 ROM | TurboSound ON/OFF | — |
👉 Notes:
- Switch 2 (middle) controls TurboSound enable/disable in all modes
- “—” means the switch position is ignored
- Other switches are reserved for future features
If tape loading fails:
- Check transistor Q1 (BC517)
Different manufacturers use different pin layouts:
Variant A (standard):
1 = Collector
2 = Base
3 = Emitter
Variant B (reversed):
1 = Emitter
2 = Base
3 = Collector
👉 Fix:
- If using Variant B → rotate transistor 180°
❗ Incorrect orientation = tape loading will not work
It is recommended to use a CMOS-based Z80 CPU.
NMOS variants may work, but compatibility is not guaranteed.
- Designed for retro compatibility + modern convenience
- Ideal for:
- Demo scene enthusiasts
- Hardware hobbyists
- ZX Spectrum collectors