Read speed rates

[dbminter]

Are Read speed rates set as a flag on each disc?  Like how recordable discs have their rated Write speeds set on the physical media itself?  Or is that even relevant?  Is it entirely set in the drive's firmware?  Or is it a combination: there's a maximum rated Read speed on the media and it's down to the drive's firmware to support that maximum speed or less? 

 

 

Thanks!

[LIGHTNING UK!]

I'd imagine it's just something in the hardware/firmware.