<![CDATA[ChipMusic.org - Variable clock for NES?]]> 2014-01-21T14:31:59Z PunBB https://chipmusic.org/forums/topic/13233/variable-clock-for-nes/ <![CDATA[Re: Variable clock for NES?]]> Switches are noisy by default, if you want a clean switch over you have to debounce some how. For clocks, you could use a 2 to 1 mux, controlled with a switch  and a RC debounce circuit. Of course, this doesn't help at all if the CPU can't handle the phase errors between the clocks.
  Also with overclocking, it's not just the CPU but the whole system that is running faster, so if rom and ram chips can't respond fast enough, there will be glitches and crashing.
Another idea, if you used the LTC, you could have a fixed R for the normal NES clock f, and a pot for variable f; and then switch between the two.This might avoid phase error.
Yogi

]]> https://chipmusic.org/yogi 2014-01-21T14:31:59Z https://chipmusic.org/forums/post/198642/#p198642 <![CDATA[Re: Variable clock for NES?]]> MostlyToast wrote:

A higher quality switch won't have as much noise/resistance which lowers the chance of a crash when switching between clock speeds.

If indeed it is noise causing the problems. Take for example your LTC clock trace, which overlaps with the defulat clock. If the leading edge of your default clock occurred after the leading edge of the LTC, say for example only 1ns afterward, then the microcontroller may see this as 60MHz as opposed to the 33Mhz, or 4.193MHz.

]]> https://chipmusic.org/Jazzmarazz 2014-01-21T04:40:03Z https://chipmusic.org/forums/post/198601/#p198601 <![CDATA[Re: Variable clock for NES?]]> Alley Beach wrote:

nb4 watercoolednes.jpg

Custom PC builders scare me.

On another note, I've been considering doing this for awhile, too! Guess I should go LM1799 shopping!

]]> https://chipmusic.org/Another+Castle 2014-01-21T04:28:34Z https://chipmusic.org/forums/post/198599/#p198599 <![CDATA[Re: Variable clock for NES?]]> A higher quality switch won't have as much noise/resistance which lowers the chance of a crash when switching between clock speeds.

]]> https://chipmusic.org/MostlyToast 2014-01-21T03:58:25Z https://chipmusic.org/forums/post/198596/#p198596 <![CDATA[Re: Variable clock for NES?]]> I heard that if you used a good switch it wouldn't crash as easily?? Either way I'm probably just going to shove a getlofi kit into it. Thanks for the info.

]]> https://chipmusic.org/DMGer 2014-01-21T03:54:18Z https://chipmusic.org/forums/post/198595/#p198595 <![CDATA[Re: Variable clock for NES?]]> DMGer wrote:

So I would be able to deal with a switch but it would be much cooler to have a pot. Would you be able to add this in addition to the switch?

Easily but most systems are prone to sudden crashes when switching between crystals or other oscillators like the LTC1799. That being said, if all you wanted to do was use a regular clock sometimes, then switch off the console and flip the clock switch, then power it back on; you'd be alright. Once you're using the LTC1799 as your clock source, the pot should not crash the system, similar to the gameboy.

]]> https://chipmusic.org/Jazzmarazz 2014-01-21T03:20:16Z https://chipmusic.org/forums/post/198591/#p198591 <![CDATA[Re: Variable clock for NES?]]> So I would be able to deal with a switch but it would be much cooler to have a pot. Would you be able to add this in addition to the switch?

]]> https://chipmusic.org/DMGer 2014-01-21T03:01:46Z https://chipmusic.org/forums/post/198590/#p198590 <![CDATA[Re: Variable clock for NES?]]> I was about to make a thread asking this! Sweet!

]]> https://chipmusic.org/DMGer 2014-01-21T02:45:58Z https://chipmusic.org/forums/post/198588/#p198588 <![CDATA[Re: Variable clock for NES?]]> Here is yet another over clocking how-to
http://kyorune.com/modding/article.php?id=67
With a 'turbo' switch setup.
Yogi

]]> https://chipmusic.org/yogi 2014-01-21T01:48:23Z https://chipmusic.org/forums/post/198581/#p198581 <![CDATA[Re: Variable clock for NES?]]> Here is a French site that might be of interest. Over/under clocking with an
LTC1799 variable clock
http://furrtek.free.fr/?a=nesclock
May try this at some point.
Yogi

]]> https://chipmusic.org/yogi 2014-01-21T01:40:53Z https://chipmusic.org/forums/post/198580/#p198580 <![CDATA[Re: Variable clock for NES?]]> nb4 watercoolednes.jpg

]]> https://chipmusic.org/Alley+Beach 2014-01-20T23:05:52Z https://chipmusic.org/forums/post/198551/#p198551 <![CDATA[Re: Variable clock for NES?]]> Thanks for the help tongue

]]> https://chipmusic.org/D3LL 2014-01-20T20:32:47Z https://chipmusic.org/forums/post/198542/#p198542 <![CDATA[Re: Variable clock for NES?]]> Depends on the frequency range you want. 555 timers can be wired in a astable mode which outputs a square wave determined by an RC equation. Make sure you calculate the duty cycle to be exactly 50%.

http://www.next.gr/oscillators/astable/ … l7889.html

But the common method the gambeoy uses is with an LTC1799 IC. It is easier to calculate the frequency range. One pot, and two resistors.
read the datasheet. wink

As discussed here though, Overclocking the 2a03 affects both the sound and video. Also the maximums and minimums have never really been tested. A high clock frequency could cause over heating.

]]> https://chipmusic.org/Jazzmarazz 2014-01-20T20:28:53Z https://chipmusic.org/forums/post/198541/#p198541 <![CDATA[Variable clock for NES?]]> Is there any way to change the clock speed on the NES via a variable clock, such as the gameboy versions used changing a pitch?

]]> https://chipmusic.org/D3LL 2014-01-20T20:15:57Z https://chipmusic.org/forums/post/198540/#p198540