[EE OVERCLOCK]: should we support overclocked PS2?

[israpps]

I know that for such thing, changes should be made on PS2SDK at certain parts of code.

I'm not even sure where to begin with, so I thought it was a good idea to open an issue to discuss it here.

I'll soon get a Namco system 256.

This model, along with system 148, these are the only overclocked PS2s in the world.

According to grimdoomer post on Twitter, the system256 RAMBUS is working at 500MHz (usual freq was 400)

Maybe add a compile time config to deal with this, so that normal PS2SDK remains the same.

[uyjulian]

If EE Core COP0 Count (reg 9)/Compare (reg 11) (usually running at EE core speed ~294.912Mhz) runs at a different speed from the EE timer related registers (which can use either BUSCLKs 147.456Mhz OR H-blanks), then this can be resolved by changing the usage of the EE core COP0 registers to the EE timer related registers.

The cpu_ticks function is the only function in ps2sdk that access the COP0 Count register, and the only usage in ps2sdk is not used for anything timing related.

[sp193]

How does the DRAM clock speed affect any part of the SDK? Is the EE core clock rate the same?

[israpps]

How does the DRAM clock speed affect any part of the SDK? Is the EE core clock rate the same?

I'm not sure...

But I guess it has to affect in some way

Otherwise, why would Namco add a jumper to set the freq back to 400mhz for backwards compatibility

[sp193]

I believe that games may have been made with a certain hardware performance in mind. Changing anything after the game's release, may be disastrous for compatibility. This was from the era when there were no downloadable updates.

Do you have any idea under what circumstances would one use 500MHz mode and when it should not be used?

[israpps]

I believe that games may have been made with a certain hardware performance in mind. Changing anything after the game's release, may be disastrous for compatibility. This was from the era when there were no downloadable updates.

Do you have any idea under what circumstances would one use 500MHz mode and when it should not be used?

On system 256, the 500mhz mode is labeled as 256

And the 400mhz one is labeled 246+

So I guess it was solely for backwards compatibility...

I'm still waiting for a system256 to arrive

When I have it, I might test if it affects wLaunchELF and other homebrews.