How does a PlayStation 1 (PS1, PSX / PSone) Modchip work?

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Shadow
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Admin / PSXDEV
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Joined: December 31st, 2012, 5:37 pm
PlayStation Model: H2000/5502

How does a PlayStation 1 (PS1, PSX / PSone) Modchip work?

Post by Shadow » September 9th, 2012, 3:52 pm

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How does a PSX Modchip work?
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Whenever you put in a legitimate PlayStation black CD-ROM, you know it will work. Why? Well, in quick easy words, it has been pressed at a factory with a special code that is in the nanometers thin range near the center of the disc. This, is called the "Wobble Groove".

What does the 'Wobble' contain?
It contains a special string of letters which the PSX looks for on boot. The wobble does exactly as it is named. It 'Wobbles'. This causes 1's and 0's which make up the special code that the PSX looks and waits for on boot.

What are the special letters?
SCEE, SCEA or SCEI (depending on your region).
Original SCEE: 1 00110101 00, 1 00111101 00, 1 01011101 00, 1 01011101 00 = S C E E
Compressed SCEE: 100110101001001111010010101110 = SCEE
It is also now known that some special disc's (Yaroze boot discs) Sony made have SCEW.

Can I see the Modchip Assembly code?
Yes. You may see it over here.

So how does a Modchip help us?
Well, as we know, the signals consist of SCEE, SCEA, or SCEI characters. The modchip simply injects one of the SCEx characters (depending on the modchips code) into the needed wire at the correct time. This then tricks the CD-ROM controller that is has received the boot signature. This then allows the system to continue with its boot sequence so that you may happily play your game backup or homebrew code on the PlayStation 1.
Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

Development Computer: Windows 98, Pentium 3 [400MHz], 128MB SDRAM, DTL-H2000, DTL-H201A, 21" Sony Trinitron CRT, CD-ROM burner, 3.25" and 5.25" Floppy Diskette Drives and a ZIP 100 Diskette Drive.

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gwald
1997 Yaroze Enthusiast
1997 Yaroze Enthusiast
Posts: 234
Joined: September 18th, 2013, 8:44 am
I am a: programmer/DBA
PlayStation Model: Net Yaroze
Location: Australia
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Re: How does a PlayStation 1 (PS1, PSX / PSone) Modchip work

Post by gwald » May 1st, 2016, 8:47 pm

I've just emailed these guys asking if they can press wobble data.
I didn't say why I wanted to tho :D
Does SCEW work on all regions?

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