Monitors are analog (seconds), video cards are digital (pixels). The pclock (pixel clock) is the coversion tool that translates seconds into pixels -- it defines the number of pixels per second that a video card sends to a monitor.
Pixel clock = Number of Horizontal Pixels x Number of Pixels Rows (lines) x Refresh Rate
Be aware that the Number of Horizontal Pixels = active pixels (ones that display data) and blank pixels (blank pixels that give a CRT the time it needs to position the electron beam in the correct spot), this also applies for pixel rows.
So, you could really state it this way (if it makes it any clearer)
Pixel clock = (Active Pixels + Blank Pixels) x (Active Pixel Rows + Blank Pixel Rows) x Refresh Rate
High pixel clocks are needed for high resolutions (or fast ones), low pixel clocks are needed for low resolutions (or slow ones)
Arcade monitors usually run at around 7mHz (though some go a little lower, all the way down to 5mHz for very low resolutions). This is why you want a video card that can handle very low pclocks for an arcade monitor as they run very low resolution displays. ATI cards and Trident's Blade T64 can handle pclocks as low as 5 (possibly lower, though it doesn't matter), Matrox's G400 can go down to 6, Nvidia cards can go down to 8, and Ultimarcs ArcadeVGA doesn't really have a lower pclock limit, meaning it can display ridiculously low resolutions. This is why if your running AdvanceMAME on a 15kHz monitor you really should get a card that supports a pclock of at least 6, as anything over 7 could be restricting.
As far as AdvanceMAME is concerned, video cards support very high pclocks, so they have no effect on the upper limit of your setup. This means that the limiting factor for a high pclock rate is your monitor. But it is only fair to say that you can pretty much ignore the high plclock number as most monitors can't display resolutions large enough to max it out. For example, I have a pclock of 5-90 in my config file but I know my monitor doesn't support a pclock over 25. So I suggest you just leave the upper pclock at 90 unless you have probs. The lower pclock limit is mostly an issue because video card manufactures don't realize that there are people like us that run their video cards at very low resolutions. Their focus is on very high resolutions, which is what most people look for in a modern card.
From your specs, we can see that your monitor supports a 50mHz bandwidth. This is how many pixels per second your monitor can legitimately handle (its pclock). So technically speaking you could use a pclock from somewhere between 5-50 to 8-50, depending upon what video card you were using. It's only fair to say that since your monitor doesn't support a resolution lower than standard VGA, then you really don't need a pclock lower than 25. So for you the lower limit of a video card's pclock is irrelavant, as they all can go down to 25mHz, which is right around were vga signals start. So technically speaking you should use a pclock setting of 25-50. For your setup, however, I'd stick to the default 5-90. This just enables all pclocks. In your case AdvanceMAME will never call a pclock your setup can't support, assuming you are using the correct hclock and vclock settings. Lucky for you, for others it's not so simple.
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Topic: AdvCfg PCLOCK value for my WG9100? (Read 1718 times)
