Use it a lot.

so if everything is happening slower doesnt that rule out pushing hardware past its limit? I wanna test this. what exactly do i need to do with the v command to crash my dmg?

The CPU performs manipulations of bits and bytes at addresable memory locations. Each process requires no thought per se. It will do no more or no less than it would in a single clock cycle when the speeds are altered.

The only time you see different reactions to the limited commands is when it starts losing data or accessing data before it actually gets to the specific locations.

No because the CPU speed is clocked off that crystal. You clock it slower, it thinks slower affecting everything from reading the joypad inputs, to drawing the screen, to controlling the PAPU sound channels. Its like running a cassette tape slower, the pitch is lower but so is everything else.

a ltc1799 on a variable resistor piggybacks on the crystal. what then?  it is still using the original hardware, only feeding it a bogus signal. wouldnt that be more like a ram upgrade?

The CPU is doing all the thinking, so if you put a crystal in it, its working slower on everything, including the time it takes to think. Pitch halving is a bonus, but the resulting speed decrease is problematic in other places like drawing the cursor on the screen.

how does it work?

Lol, not exactly how it works.:P

wouldn't the cpu have more time to think?

Yea but with a lobotomized cpu, v commands may very well cause crashes as they can be very cpu intensive.

Once notes get that low, I know most of the bass will be unhearable through most speakers. mainly I'm interested in experimenting with the noise channel and some synth sounds, and abusing V commands. I'll try it out with a GBC

the oscillatior i got must be different somehow because it is really stable. maybe because i added no trim resistor?

A lot of frequencies are filtered out with many cheap sound systems and even more headphones. I can't listen to chip on the go at all...my phone sounds that bad.

Just for the record, the C2 that the wave channel can produce is lower than even most subwoofers can reproduce effectively. It's 65hz, human hearing bottoms out around 20hz.  2 octaves below 65hz is around ~16hz just for the record. 

Now I know it would be great if the pulse channels could also be an octave lower, but to not be able to do anything complex processor-wise is very limiting for little benefit IMO

this will do quarter clock: http://store.kitsch-bent.com/product/quint

its really not that practical at quarter speed.  like herr_prof said, the UI is unusable because of the lag.  if you've ever played a computer game where the graphics are set to wayyyy to high a detail/refresh/etc, and there is a good few seconds between moving/clicking with the mouse and getting the software to respond?  thats what its like. 

i'm not even sure if it was even down to quarter speed before it stalls, its not much good past right below half speed so i made that the bottom in the code. 

if you're curious, use a half-clock for the DMG with a Game Boy Color.  This would be a GBC's quarter-clock speed.  granted, the CPUs are different so its not a fair comparison.