Curious side effect with an AGP board

[dkintana]

I have several AGP boards that was playing with while making my DOS station. Some of them were made with an S3 chip (Trio 3D[362], Trio 3D2X[368])and all of them suffer from the same effect: Many lines across the screen in text mode like the interferences produced by mobile phones just before they start ringing (Sure all of you some times have seen this kind of interferences). In graphics mode (Windows 3.11) there is an horizontal thin black line going continuosly from bottom to top.

Well. When I load USBUHCI{L}, all kind of interferences dissapear

What is producing this collateral effect? What kind of hardware tweack made USBUHCI{L} that corrects the image in my AGP card?

[Bret]

I really have no idea, but suspect one of two things. Either it's a timing issue, and USBUHCIL slows things down enough that the timing issues are resolved, or maybe the AGP and USB hosts controllers are sharing the same IRQ and somehow USBUHCIL is "fixing" the AGP IRQ handler code.

I don't use AGP on any of my systems, so don't have any experience there. I have had problems in the past with systems that use shared video memory, so always install a "real" video card), and also disable the video IRQ in the BIOS (if the BIOS lets me do that).

[Crypticalcode0]

On the PCI bus the S3 Virge (Not even on the ISA bus) doesn't pull that stunt.
As for AGP you can run into similar problems using a Hercules card.

It's a system timing issue most likely.

I can not reproduce this on any of my systems, and i have 3 AGP systems one with even some ISA slots on it.
None of the 7 S3 Virge's i tried seem to have this problem but they are PCI slot cards.