24-02-2022, 09:01 AM
(23-02-2022, 10:04 PM)mjelic Wrote: Is there any way to find out what speed your machine is running at? My 128k has the A versions of both CPU and PIO.
Quick answer : 3.375Mhz
All Microbees, apart from very early kit & production machines (1982) run at 3.375Mhz.
The only other exception is the early production of 256TC machines which were software switchable
between 3.375Mhz & 6.75Mhz. 6.75Mhz was unstable though, so support was removed.
Writing a routine to check approximate execution speed of the Microbee probably wouldn't be too hard
if you based it around detecting CRTC vertical retrace time that can be detected through the 6545 screen
controller registers.