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Biostar A785GE, screen won't come on w/ DVI

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May 30, 2010 9:08:04 AM

Hello, I would really appreciate some help with a problem I am having with a new system I am trying to get built. I have never come across an issue like this before.

I have just acquired a new Biostar A785GE v6.4 motherboard, AMD Athlon II 64 245 CPU, and 2 x 2GB PQI DDR2 800 memory.

Have completed installing the motherboard/cpu/ram into my case and I have a strange issue. Upon initial startup, the system started with the monitor connected through DVI. But ever since then, the only way I get anything on the screen is if I start the system with the VGA cable connected. If I leave both cables connected it will start through VGA and then I can unplug the VGA cable and it will switch to DVI, but now it won't POST using only DVI. I have tried resetting the cmos, and even removed the battery and started the system and this made no difference. Also, there are no PCI cards installed and the only things connected are keyboard/monitor/mouse. I tried using a DVI-to-VGA adapter also so I know the monitor is not the problem.

This seems odd to me, as I'd think the system should start through DVI every time. Am I doing something wrong, or is this a normal occurrence, or?

Thanks!
May 30, 2010 10:20:32 AM

ok i have now noticed that the input to the monitor is 1280x1024 thru DVI and it's 720x400 thru VGA, these resolutions are both @ the info screen (point before hdd boot because i have no hdd's connected now). I have searched the bios for something that would tell the board to default to one video output or the other, but there is nothing like that available. it seems like the board is simply defaulting to VGA output upon post, as the DVI does seem to work. and the system does not hang if only DVI is connected, but there is no video in text mode thru DVI unless VGA is also connected. Is it common with the AMD 785G/Radeon HD 4200 to have to startup the PC using VGA and switch to DVI within windows?

still doesn't make sense to me that the first time the system started i got a signal thru DVI at the info screen without VGA connected. I feel like I'm missing something here?
May 30, 2010 5:11:47 PM

Well, I figured it out. Can't explain this (it might be a bios setting I have not yet discovered, or simply my monitor) but if i power the screen and the tower on at the same time the system will post thru DVI. If I don't do this, the Radeon HD 4200 on the motherboard will not output a signal thru DVI upon turning the system on. So essentially my monitor doesn't want to wake up from sleep mode when turning on the system while video is connected thru DVI only.

Never had to do this before with my old system, but yes it was old. Was using a Geforce 6600GT and a socket-462 board before. In addition to the method I found above, if I unplug the power cord from the monitor and plug it back in, system posts to DVI. And I'll say it's a minor inconvienience that the monitor doesn't want to wake up from sleep mode with only DVI connected, but at least I discovered what I have to do to have the system post thru DVI. This must be some kind of issue with my monitor. Going to try another monitor/DVI cable next to see what happens.

If nothing else, I hope this thread helps someone out there. I've found a TON of similar issues regarding onboard DVI/HDMI with ATI and also Nvidia GPU's, so I'm thinking this is not something unique to my motherboard.
May 30, 2010 5:58:43 PM

Well its definitely something to do with my LCD monitor! Tried system with a DVI input on a HDTV and it posts every time. Now if only I could have my time back....

Strange how this monitor issue magically became apparent when I put together a new system. Computers can be so annoying at times, lol.
!