I always thought that the Z80 was clocked at 3.58 MHz. But when I checked the clock frequency of my NMS8245, I noticed it was 3.55 MHz. I attributed that to the fact it is over 30 years old, but today I checked the service manual and noticed it is still spot on:
This is approx 0.7% slower.
Is this a difference between MSX1 and 2 or is this specific for the 8245?
MSX Z80 clock frequency
Maybe the 823x/8245 manufacturers simply had a cache of 21.328 Crystals and wanted to get rid of them? 
@Grauw: Pal color burst is 4.43 MHz, not 3.58 and your NES example is wrong: PAL NES and NTSC NES/FC have different GPUs with different dividers, so they NEED different clock values.
A more fitting example would be the MD (or some PS1), where they used the same Video IC but slightly different clocks.
You could be right in thinking that the 8280/8245/8235 were built to better adhere to the PAL specs, and the 8250 difference may be explained by it being an adaption from an existing NTSC specced machine (MPC-25).
Anyway, the slightly clock difference is known to cause problems on other (non MSX) machines, could it be that the MSX need clock fixes too?
I think that even modern digital displays have some tolerance and don’t need exactly 50 or 60 Hz. So if the MSX provides it with 50.16 Hz or 59.92 Hz through an analog signal, it works fine. And if the MSX goes through an OSSC analog to digital HDMI converter, it will still keep the original frequency.
I’ve never seen frame hiccups with my modern digital displays at least.
Either way, this slight reduction in clock frequency does not affect MSX programmers, because if I read the NMS 8245 schematics correctly the CPU is clocked by the VDP, so they still run exactly in sync with each other.
I think it would be nice if this were emulated though! Is there an openMSX bug about this? 
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