hamilton@udel.edu (andrew hamilton) (03/22/91)
I'm thinking of purchasing a color VGA monitor and card soon for my 33MHz 386 system, but I'm not sure what the difference is between an 8 bit model and a 16 bit model. Assuming the same resolution and dot pitch, is there a noticeable difference to the eyes? They say the 16 bit is faster, but I've never seen any monitor that was too slow to keep up with a computer (except for maybe those high intensity green phosphor ones that stay lit forever). What does this mean? Is it worth the extra $100 to get a 16 bit? Thanks in advance, Andrew.
Mike_Diack@kcbbs.gen.nz (Mike Diack) (05/18/91)
Anyone know how a VGA card senses that a monitor is connected (or not) Problem : connect a sony video projector up to a vga port on a computer via a transparent interface , and nothing happens - piggyback a standard monitor on to the port and BOTH projector ond monitor work fine. How did the computer "know" that the monitor was there , and how can i dummy up the connections so the computer works into the projector WITHOUT the monitor ... all helpful hints appreciated , thanx , M.D.
richard@mee.tcd.ie (05/20/91)
> Anyone know how a VGA card senses that a monitor is connected (or not) > Problem : connect a sony video projector up to a vga port on a computer > via a transparent interface , and nothing happens - piggyback a standard > monitor on to the port and BOTH projector ond monitor work fine. How > did the computer "know" that the monitor was there , and how can i dummy > up the connections so the computer works into the projector WITHOUT > the monitor ... all helpful hints appreciated , thanx , M.D. I think the solution is to ground pin 11 on the vga card to pin 10 (digital ground) this pin is monitor i/d and floats to hi if left unconnected. A similar thing happens if you boot the pc without a monitor attached, the card switches to monochrome mode and won't let you soft-switch it back up without rebooting. -Richard. Richard Bolger // Trinity College Dublin // rbolger@vax1.tcd.ie Republic of Ireland //
myers@hpfcdj.HP.COM (Bob Myers) (05/22/91)
I don't think that this is an issue of whether or not the card "knows" that
there is a monitor out there, but rather whether or not the signals are
properly terminated. Without the monitor, the gear you're using may not
terminate the video and/or sync signals in the expected impedance (75 ohms
for the video; your guess is as good as mine if you have separate sync - I
don't recall the VGA system very well at the moment). Check near the input
connectors of the video projector, interface, or whatever else you're using
for switches which may be marked "Hi-Z/75 ohms" or something like that. If
you're NOT going to use it in parallel with a monitor, then set these to the
"75 ohms" position.
Another possibility is that your gear is expecting sync from the wrong place
(there'd be a switch for this as well). This is less likely, as you say that
it works just fine when the monitor is connected in (and I assume everything
else remains the same).
Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not
Ft. Collins, Colorado | those of my employer or any other
myers@fc.hp.com | sentient life-form on this planet.Jay_R_Keller@cup.portal.com (05/22/91)
Mike Diack asked about VGA monitors. Mike, I don't know if this is related to your problem or not, but IBM monitors have 3 pins dedicated to a "monitor ID" code, which is available to the VGA (or 8514/A or XGA) card, and also to the software. OS/2 uses it, for example, to automatically install the correct display support. The code: PIN 4 PIN 11 PIN 12 Meaning n/c n/c n/c No monitor attached n/c n/c GND Mono monitor with no support for 1024x768 n/c GND n/c Color monitor with no support for 1024x768 GND GND n/c Color monitor with support for 1024x768 Maybe your projector is not providing the code to tell the VGA that it is there. If so, you can try modifying the plug. DISCLAIMER: I know this works for some Sony monitors, which support 1024x768 but don't provide the proper code to the PS/2, so they come up in 640x480. By changing the plug, the system sees the monitor as high-res-capable, and configures itself for 1024x768. Whether grounding pins in your plug will your projector, however, I can't say (although I doubt it). Good luck. Jay Keller
nitinj@chips.com (Nitin Joshi) (05/25/91)
The VGA card has 75 or 150 ohm terminating res on the card, the moniter also has a 75 ohm terminator, The VGA DAC is a current output DAC and so depending on if the moniter is connected or not, the voltage level on RGB lines is different. A comparator senses this and determines no/mono/color moniter, mono moniter usually has terminator res on G only. This is done immediately after hardware reset i the PC. Your sony may have switchabke terminator res or may not have it at all.You could build a 15 pin plug w ith terminator res, use that to power on and then switch the plug with the sony, or modify sony to include the res
mcovingt@athena.cs.uga.edu (Michael A. Covington) (05/25/91)
According to the IBM manual, specific pins on the VGA connector are grounded to indicate a monochrome or color monitor. It's nothing nearly as subtle as measuring terminating impedances. -- ------------------------------------------------------- Michael A. Covington | Artificial Intelligence Programs The University of Georgia | Athens, GA 30602 U.S.A. -------------------------------------------------------