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PostPosted: Sat Mar 12, 2005 4:35 am 
Hi all,

are there any methods that I can drive NES into
a "power-saving" or "sleep" mode so that minimal
power will be consumed while it can be awakened
by timers?

Blanc


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PostPosted: Sat Mar 12, 2005 5:19 am 
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There's no feature like that, really. Maybe if the PPU's output and NMIs are disabled, and the program just sat on a "here: JMP here" in (internal) RAM. Then it could be 'woke up' by an external IRQ.

I doubt it would save much power though, if any at all. It would put a stop to cartridge memory reads at least.


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PostPosted: Sat Mar 12, 2005 6:28 am 
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You could press the power switch and set a timer to remind you to power it back on later. I think I got both requirements covered :)


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PostPosted: Sat Mar 12, 2005 8:21 am 
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The NES wasn't designed to run off batteries, and it was designed before governments started giving tax breaks for "green" computing.


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PostPosted: Sun Mar 13, 2005 10:02 am 
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The best way to save some power is to turn it off. Some battery backed games like Fire Emblem and Just Breed have a "suspend" mode, it doesn't actually save the game, but it just allow you to turn the power off and continue the stage later, but this isn't a save scince you can't restore it if the game is over.

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PostPosted: Fri Mar 18, 2005 5:56 pm 
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Well, it's possible to install a device on NES to cutoff the video/audio output signals via 4017h port. A proper blueprint wouldn't be so hard. I don't know the GBA sleep mode though, but I believe it's possible.

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PostPosted: Fri Mar 18, 2005 8:42 pm 
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GBA has two sleep modes:
  • "Halt" stops clocking the CPU core until an interrupt is triggered but leaves the audio, the PPU, and background DMAs running. It's commonly used to wait for the vblank.
  • "Stop" stops clocking CPU, PPU, and audio until an interrupt is triggered.
The Super NES has Halt as well by executing the 'wai' instruction.

But because of how NES sound works, where one clock runs both the CPU and the audio but there is no 'wai' instruction like on 65c816, I don't think it'd be possible to make Halt. Stop, on the other hand, would involve intercepting the master clock signal on the NES mainboard.


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PostPosted: Sat Mar 19, 2005 2:09 pm 
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tepples wrote:
GBA has two sleep modes:
  • "Halt" stops clocking the CPU core until an interrupt is triggered but leaves the audio, the PPU, and background DMAs running. It's commonly used to wait for the vblank.
  • "Stop" stops clocking CPU, PPU, and audio until an interrupt is triggered.
The Super NES has Halt as well by executing the 'wai' instruction.

But because of how NES sound works, where one clock runs both the CPU and the audio but there is no 'wai' instruction like on 65c816, I don't think it'd be possible to make Halt. Stop, on the other hand, would involve intercepting the master clock signal on the NES mainboard.


Are there any SNES games that make use of the "wai" instruction?


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PostPosted: Sat Mar 19, 2005 8:28 pm 
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Jagasian wrote:
Are there any SNES games that make use of the "wai" instruction?


Many, I'm sure. I used it in my NSF player to wait for vblank (NMI).


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PostPosted: Sat Mar 19, 2005 9:37 pm 
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I'll take a wild guess that at least Wai Wai World 2 uses it.


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PostPosted: Sat Apr 09, 2005 12:57 am 
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Okay, here's my idea for a sleep mode.

1. Disable sprites and background bits in $2001.
2. Disable sound bits in $4015.
3. Execute the undocumented opcode KIL or HLT.
4. Make damn sure your victim knows to hit the reset button.

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PostPosted: Sat Apr 09, 2005 1:06 am 
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Why is this thread still open? :shock:

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PostPosted: Sat Apr 09, 2005 1:22 am 
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Because the admin and mods will it so!

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PostPosted: Sat Apr 09, 2005 12:38 pm 
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It is always better to post in an existing thread than to start a new one.


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PostPosted: Sun Jul 24, 2005 6:54 am 
So can you just put the NES in stop mode whenever you want by cutting the CPU clock? I thought the 6502 had dynamic registers, and that would wipe them out.


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