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PostPosted: Tue Oct 02, 2018 1:43 pm 
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edit: Corrected the post back to what actually works:

Use these two game genie codes:

AZUZIGPA
ONEPNPZE

Now US version of "The Legend of Kage" becomes an Input Lag tester. It copies your joypad into PPUMASK every frame. Hold A to toggle the monochrome bit.

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Last edited by Dwedit on Wed Oct 03, 2018 11:57 am, edited 3 times in total.

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PostPosted: Tue Oct 02, 2018 3:04 pm 
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This is what NES+CRT input lag looks like:

Taken with phone camera in "8x slow motion", recording at 120FPS.
Notice how on the third frame, finger makes contact with the button, and the screen is instantly illuminated at the top.

0 lag whatsoever.

Attachment:
inputlag_nes.gif
inputlag_nes.gif [ 176.73 KiB | Viewed 1361 times ]

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PostPosted: Tue Oct 02, 2018 3:13 pm 
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Huh that's neat. What's the story behind coming up with this?


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PostPosted: Tue Oct 02, 2018 3:34 pm 
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AZUZIGPA: A435?01:20

First code patches the joypad loop to write its result to $2001 (PPUMASK) instead of the joystick state variable.

Code:
 00:A40C: A2 07     LDX #$07
>00:A40E: AD 16 40  LDA JOY1 = #$00
 00:A411: 29 03     AND #$03
 00:A413: C9 01     CMP #$01
 00:A415: 6E 03 01  ROR $0103 = #$00
 00:A418: AD 17 40  LDA JOY2_FRAME = #$00
 00:A41B: 29 03     AND #$03
 00:A41D: C9 01     CMP #$01
 00:A41F: 6E 04 01  ROR $0104 = #$00
 00:A422: CA        DEX
 00:A423: 10 E9     BPL $A40E
 00:A425: A5 C2     LDA $C2 = #$00
 00:A427: 30 1A     BMI $A443
 00:A429: AD 03 01  LDA $0103 = #$00
 00:A42C: A6 C4     LDX $C4 = #$00
 00:A42E: F0 03     BEQ $A433
 00:A430: AD 04 01  LDA $0104 = #$00
 00:A433: 8D 01 01  STA $0101 = #$00 <- Patch to STA $2001 (PPUMASK)


Next patch makes a branch loop back to the joypad polling code.
ONEPNPZE: 9987?02:F9

Code:
 00:9981: 20 F7 A3  JSR $A3F7
 00:9984: E6 21     INC $21 = #$00
 00:9986: D0 02     BNE $998A        <- Patch to become BNE $9981

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Here come the fortune cookies! Here come the fortune cookies! They're wearing paper hats!


Last edited by Dwedit on Wed Oct 03, 2018 12:02 pm, edited 2 times in total.

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PostPosted: Tue Oct 02, 2018 4:00 pm 
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Location: Canada
Heh, that's an interesting hack.


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PostPosted: Wed Oct 03, 2018 7:37 am 
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Patch a rom with GG codes permanently:
https://www.romhacking.net/utilities/1054/


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