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28 votes
Accepted

Why is the 8254's default rate 18.2 Hz?

The first CGA PCs used a single clock from which they derived all their timings. To allow for NTSC output, the main clock had to run at a multiple of the colour subcarrier frequency; the main clock ...
Stephen Kitt's user avatar
8 votes
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Are there any known 8086 systems that would dynamically switch between XTAL and EFI clocks on 8284 clock generator?

I's be rather surprised if anyone ever did. F/C is a static input, not meant to be switched at runtime. There are not only no examples for switching, but it's as well clearly stated on page 3-392 of ...
Raffzahn's user avatar
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6 votes

How to teach the Z80 to count milliseconds and microseconds like Arduino?

Way 2.1 to pin a non-masked interrupt, attach a crystal with a frequency of 10KHz (not sure about this value, but with another value idea is same), and in the non-masked interrupt handler, increase ...
比尔盖子's user avatar
  • 3,104
5 votes

How to teach the Z80 to count milliseconds and microseconds like Arduino?

You have correctly surmised the two approaches to measuring time, not just on the Z80 but in computers in general. With a processor like the Z80 where every instruction takes a known number of ...
RETRAC's user avatar
  • 13.6k
4 votes
Accepted

How to teach the Z80 to count milliseconds and microseconds like Arduino?

Now I'm stuck - I need to be able to count milliseconds and microseconds in the code. Forget about microseconds. Single instructions on a Z80 are already in the range of 1 µs or even longer, ...
Raffzahn's user avatar
  • 219k
2 votes

How to teach the Z80 to count milliseconds and microseconds like Arduino?

your best bet would be to hook up binary counter directly to your CPU clock and use it as divider that creates interrupt ... For example if you got 4.0MHz and want ~1ms resolution then divide the ...
Spektre's user avatar
  • 7,238
1 vote

Are there any known 8086 systems that would dynamically switch between XTAL and EFI clocks on 8284 clock generator?

My Turbo XT, which has a clone of the DTK PIM TB10 mainboard, picture of the original (10MB!) at http://www.minuszerodegrees.net/xt_clone_bios/DTK%20PIM-TB10-Z%20of%20revision%209.jpg seems to do ...
Michael Karcher's user avatar

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