Peripheral 3 Register

Number	$08
Readable	Yes
Writable	Yes
Short Description	ABC/ACB Stereo, Internal Speaker, SpecDrum, Timex Video Modes, Turbo Sound Next, RAM contention and [un]lock 128k paging.

(R/W) 0x08 (08) => Peripheral 3 setting:

 bit 7 = 128K paging enable (inverse of port 0x7ffd, bit 5) 
         Unlike the paging lock in port 0x7ffd, 
         this may be enabled or disabled at any time.
         Use "1" to disable the locked paging.
 bit 6 = "1" to disable RAM contention. (0 after a reset) 
 bit 5 = Stereo mode (0 = ABC, 1 = ACB)(0 after a PoR or Hard-reset)
 bit 4 = Enable internal speaker (1 = enabled)(1 after a PoR or Hard-reset)
 bit 3 = Enable Specdrum/Covox (1 = enabled)(0 after a PoR or Hard-reset)
 bit 2 = Make $FF Timex port readable (covers "floating bus") (0 after a PoR or Hard-reset)
 bit 1 = Enable TurboSound (1 = enabled)(0 after a PoR or Hard-reset)
 bit 0 = (core 3.0) Selects issue 2 keyboard

https://www.specnext.com/tbblue-io-port-system/

NEW in core 3.0:

 bit 4 default 0
 bit 0 set selects issue 2 keyboard