VCLK question

[altheos]

Hello,

Can someone explain how multiples VCLK is handled in Pcem ?
I found out (or maybe i'm totally wrong) that there is one svga clock and two fixed const but in case of more ?
Regards.

[SarahWalker]

It depends on the emulated card. Which one are you using?

[altheos]

I use Trident ones. There is differences between TGUI9440 and 8900D : one use calculated VLCK and the other register fixed ?

[SarahWalker]

The clock chip used with the 8900D provides a number of fixed frequencies. The TGUI9440 has a programmable PLL which allows it to generate a much wider range of frequencies.

[altheos]

Ok thanks for the clarification Sarah. So, in theory, i could generate a 80 Mhz VCLK. True ?
And how is this frequency simulated with pcem ?

[SarahWalker]

The card sets svga->clock, the SVGA code then uses this when calculating horizontal display and blanking periods.