Re: [CAD_CAM_EDM_DRO] Mach3 & "integrated video"

Danny Miller wrote:

> Well, what confuses me is that isn't the parallel port on the
> southbridge and video on the northbridge anyways?
>
> Logically I'm not sure if northbridge traffic would interfere with
> southbridge. But even assuming it could, the real mysterious part there
> is that doesn't an integrated video system run through the northbridge
> pretty much the same as if it were running through the AGP port?
>

it has NOTHING to do with the PCI bridges, and everything to do with
memory cycles. When the graphics card does a big bit-block transfer,
like sliding an entire window around the screen or revealing a hidden
window, it can saturate any memory on the system. If that is the
graphics card's OWN memory, no problem. If it is the main system
memory, the CPU can be almost completely locked out for milliseconds.
If the step generation thread needs service every 25 us, it will miss
perhaps 40 dispatch intervals, and cause all motors to jam to a stop for
a ms or more. Even my servo systems that typically only need one update
per ms would suffer under these circumstances.

Jon