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PS1 PS1 Modchips

Strogen

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Jun 11, 2019
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I'm looking to install some modchips in my PS1's. What's the best chips for these? I've got a SCPH-9001 NTSC and a SCPH-7501 NTSC.
 

Trimesh

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Trimesh
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The two traditional options are MM3 and Mayumi 4 - there is also the stealth version of PsNee (discussed here http://www.psxdev.net/forum/viewtopic.php?f=47&t=1262) - which uses a different stealth approach and runs on an Arduino board. This may be easier for you to get your hands on.
 

FREE_WORLD

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May 30, 2019
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davesandell
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October 2nd 2012
If I were doing them I would go for the full-fat 8 wire Mayumi v4 install.... Very reliable (as uses the PS1 clock - rather than the osc in the PIC) and has stealth code...
Also good quality media helps if you should run backup CDs. You get what you pay for - particularly with media....
Can't beat a quality original PS1 game :)
Feel free to PM if you need chips/install - or wish to discuss further...
 

Trimesh

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The code for the PU22/PU23/PSone that's used in MM3 is identical to the Mayumi 4.0 code (in fact, it was probably copied from Mayumi) - the only practical difference is that the MM3 uses the internal oscillator and the Mayumi code uses the mechacon clock.

In theory, the internal oscillator should be fine - it's not terribly accurate, but the datastream is basically asynchronous serial, so it only needs to be close enough that it stays in sync for a single character. It got a bad reputation because some of the older programming software corrupted the oscillator calibration value that's stored in the last word of ROM and this made the chip run at the wrong speed.
 
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