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Hammy

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Overclocking the Megasystem 1
GUIDE

I keep getting asked so the information is now compiled here separate.

1. 6.00 MHZ STANDARD

2. 8.00 MHZ / 10.00 MHZ (STABLE)

3. 12.00 MHZ (NOT STABLE)




8 / 10 MHZ
---------------------

To overclock to 8 or 10 mhz a cpu replacement is not always needed if your original CPU can cut the mustard.
It's worth testing the faster clock before thinking about a replacement.

To perform the mod:

1)
Lift pin 4 of IC M21 IC HC04 (no longer connected)

2)
Install a 8mhz or 10mhz 4 pin OSC into the empty location @ D8
Connect the power and Ground pins (one will be missing and need jumping from the bigger pinout.
(Don't use position F1 the PWR + GND is messed up)

3)
Add wire from the osc out to MAINCPU (5C - pin 15)

4)
Good to test, use rodland or something, if it's not stable at 10mhz consider CPU replacement to P12/P16 or going for 8mhz that is within spec. of the original processor.



12.00 MHZ (NOT STABLE)
-----------------------------
An easy mod but never works :)
Maybe it will work on some boards but this has been tested on 3 setups now not stable.

1) Lift pin 4 of IC M21 HC04 (no longer connected)

2) Add wire from Pin 8 IC M21 HC04 to the now empty pin 4.

3) Good to test, use rodland or something, if it's not stable remember you are pushing luck so drop down lower.




----------------------------------

ADDING A SWITCH:

Not a problem, 3 position switch.
Middle pin = CPU clock pin
1st Side = Pin 4 of the HC04 (isolatedfrom the board)
2nd Side = New clock signal (OSC Output)

------------------------------

GAMES WITH SLOWDOWN:

Rodland - Slowdown improvement with any overclock, still seems to drop @ 10mhz+ (code issue i guess...)
EDF - Slowdown improvement with overclock best @ 10mhz+
Big Striker - REQUIRES 10mhz OR BETTER or Unstable!
Phantasm - Slowdown improvement with overclock best @ 8mhz+
P47 - Slowdown improvement with any overclock, still seems to drop @ 10mhz+ (code issue i guess...)
ST dragon - This had some slowdown @6mhz but not tested on an overclocked setup yet.

Others?
 

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Hammy

Enlightened
Joined
Feb 3, 2018
Messages
1,418
Reaction score
2,958
Location
U.K
NEW HACK 7MHZ - no added clock, used 7mhz from onboard!

1) Lift pin 4 of IC M21 74HC04 (no longer connected)

2) Add wire from Pin 6 IC H3 74HC04 - MAINCPU 5C - pin 15
 

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