mcleod_ideafix escribió:7MHz support for ZX-Uno is scheduled to be available at the same time as full Chloe support. Andrew, which is the ZXI port used for speed control?
PRISM uses the lower four bits of port 0x8e3b to select the speed multiplier. So you can set from x1 to x15. That gives you a valid range of 3.5Mhz to 52.5Mhz. For values higher than the maximum speed, the highest available speed should be selected. Here's the code from SE Basic 4.1 (which I'll back port to SE Basic 4.0 when I have my own ZX-Uno):
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; THE 'SPEED' COMMAND ROUTINE
org 0x1903
speed:
call find_int1 ; get value
and %00001111 ; discard top four bits
ld bc, 0x8e3b ; prism CPU speed select
out (c), a ; change speed
ret ; end of subroutine