Don Superfo na grupie FB Superfo Harlequin 128 opublikował
listę zmian wprowadzanych w kolejnych wersjach Superfo Harlequin 128
"Here is the detail of each versions
Issue ONE: This is the first version, extend from Harlequin 48K so it has 48K timing.
Bug: - No 470 Ohm resistor at port 7FFD to prevent collision with Disable port signal.
Issue 1: 48K timing, add Kempston joystick port
Bug: - No 470 Ohm resistor at port 7FFD to prevent collision with Disable port signal.
- No IORQULA signal at edge connector
Issue 1B: 48K timing, add 470 Ohm resistor at port 7FFD
Bug: - No IORQULA signal at edge connector
Issue 2: 128K timing, add Kempston joystick port
Bug: - No 470 Ohm resistor at port 7FFD to prevent collision with Disable port signal.
- No IORQULA signal at edge connector
Issue 2B: 128K timing, add 470 Ohm resistor at port 7FFD
Bug: - No IORQULA signal at edge connector
Issue 2D: Support +3 ROM, add IORQULA signal at edge connector
*Issue 2E: Change master clock to be 14.318MHz
Bug: Not 100% 128K timing
Issue 2F: Use only one 74HC257 to generate RGB signal
Issue 2G: Use switch to select 48k-128K timing and PAL-NTSC mode, instead using jumper
Issue 3D: Add RS-232 port and CF-IDE port, support +3E ROM
Issue 3G: Support external +3 floppy disk
Issue 3H: Use MiniDIN 9 for RGB output
Issue 4A: Support ALLRAM mode"
* Dla wersji Issue 2D dla uzyskania 100% kompatybilności z ZX Spectrum 128+ dodatkowo zastosowałem:
1) CPU w wersji NMOS
2) poprawkę zaproponowaną przez Superfo - Sygnał CPU M1 należy podać na pin 6 U4 zamiast VCC
https://www.speccy.pl/forum/index.php?topic=271.msg98010#msg98010