Hello my friends!

This is a reminder for me and for the future generations to come. I’m not going to show you anything very magical or new, but this happen to me and I didn’t have clue about it. So if you didn’t know, now you will!

Are you tired of compsing something in Vortex Tracker and hearing something odd when playing it in the machine? Your tracker might be wrongly configured!

By default Vortex Tracker is configured for the AY installed in the Pentagon 128K, which means that the chip frequency is set to 1.75Mhz and the interrupt frequency of the machine is set to 50Hz. In the case of the MSX the correct chip frequency is close to the found in the ZX Spectrum (Wooohoooo!), so we can set 1.7734Mhz. If you’re doing music for PAL machines, you’re done. If you’re targeting systems that work with 60Hz (NTSC machines or MSX2 or superior PAL machines in 60Hz mode), you should change the interrupt frequency to 60Hz (Atari ST, in the options 🤷).

To do so just go to File, Options and then Chip emulation.

And that should be it!

I hope you do a lot of random stuff in Vortex and share with us all!

Edit: Corrections to the previous text

I previously claimed, now fixed, that the MSX AY Chip was runing at the same frequency as the Spectrum was. However this was not entirely true and I have corrected that.

Our mystical and wise friend mvac7 has done further research and here I present his conclusions:

In [1] a user claims the following:

The multiplier is 32, because the GI chip is rated to 2Mhz maximum (it can’t be clocked at 3.579545mhz) so in the MSX design it receives 1.7897725Mhz (3.579545Mhz divided by 2).

Therefore the correct frequency to be set is 1.7897725 (1.7897727272727272929131459022755734622478485107421875 if you’re very picky), as can be also seen in [2].

In the Omega MSX we have a flip-flop 74HCT74D which acts as a divider of the clock frequency, confirming the previously mentioned sources [3].

Moreover, in the service manual of the Panasonic CF2700 (Page 7)[4] we can see the following figure:

Here we see that this machine has a clock that oscillates at 10.6781522 Mhz and this is divided by 3 to obtain the Z80 clock and then by 2 (or by 6 from the original clock) to obtain the PSG clock. In this particular case the final frequency is 1.779462 Mhz far closer to the Spectrum than with the other value. So, in the end with the spectrum frequency you should be good. We may not be able to hear the difference directly from 1.779 Mhz to 1.790 Mhz. Or maybe we can say that that is the voice of your MSX, unique. Way more poetical, right?

It is true that we can manually set the values of the frequency in vortex, but it appears that it is not working as after saving the changes you get back to the previous configuration used. But you may want to double check that!

So, in summary, using the Spectrum frequency is fine.

How to config your Vortex Tracker for the MSX computers family

Published 2021-08-22 19:56:31

Edit: Corrections to the previous text