nforce can't do 16x12 at 32bit, only 16bit... Why, oh why?

[tart666]

I have an asus a7N266-VM board that is set to have 32 MB dedicated to video.

But when I change the res to 1600x1200x32 in screen properties it drops automatically to either 16x12x16 or 1600x900x32. DOes anyone know why this would happen?

 

[vss1980]

Its either detected that your monitor cant do the requested resolution and colour depth (via its profile or plug & pray), or more likely the on-chip RAMDAC of the nforce is unable to provide higher.

The RAM a graphics card/chip has is no indicator to overall resolution support as the chip must be able to push the necessary pixel information. It could be a driver limitation, but I doubt it. Also, I think you have the nforce 220 chipset which is the lesser version.... maybe the 420 and nforce2 boards are better.

 

[dawks]

The amount of memory does affect the total overall resolution capabilities of the video system, but 32megs should be more then able to handle 1600x1200x32bit..
Only thing I can think of is a monitor limitation... And/Or the RAMDAC may not be 'high-quality' enough in your particular hardware to support that resolution/color depth.

 

[tart666]

thanks guys, those are all valid reasons..

My monitor CAN to 16x12x32, i used to do it on an ATI rage pro card... (it's a Hitachi CM 751)

that leaves bad RAMDAC. Is there anyone out there with an nforce 220 that can confirm the same?

 

[vss1980]

Originally posted by: DaZ
The amount of memory does affect the total overall resolution capabilities of the video system, but 32megs should be more then able to handle 1600x1200x32bit..
Only thing I can think of is a monitor limitation... And/Or the RAMDAC may not be 'high-quality' enough in your particular hardware to support that resolution/color depth.

Yep, and if we were having this conversation years ago when graphics cards had 2 or 4 MB versions I would have given the answer you gave...... but now memory is aimed primarily at texture / Z storage, with the 2D desktop needs being taken care of a long time ago.
Ironically, the demands of the next windows with hardware 3D display of the desktop is gonna bring back these same sorts of problems (although with 128MB graphics cards starting to become the norm this may not matter either come a couple of years time).

 

[zsouthboy]

FYI monitors won't say that they can't do a certain resolution in one color mode, and not in another.

Somethings hosed with your drivers, try actually changing the amount of shared memory DOWN (just try it).

5.5 megs of ram is enough for 16x12x32 btw

 

[Pete]

The color depth has nothing to do with the RAMDAC, AFAIK. 1600 * 1200 * 100Hz = 192MHz minimum RAMDAC required.

You certainly have enough memory for it. 1600 * 1200 * 32 bit * (1 byte/8 bits) = 7.68MB RAM required.

So it may be a driver or monitor .inf issue. Are you using the latest nForce drivers? Do you have the correct monitor .inf installed? FYI, I just tried 16x12x32b on my A7N266-VM, and it worked. I'm using old nForce drivers, dated 24 May 2002--too afraid to update drivers for my whole system, don't want to corrupt the HD somehow.

 

[Peter]

Simple. Memory bandwidth. Shared-memory VGA cannot pull an infinite amount of bandwidth from the system RAM - there has to be some left for the actual computing work.

 

[Pete]

Possible, but I have a hard time believing anything in 2D is seriously using anything approaching 2.1GB/s. I'm guessing 16x12x32b uses 0.768GB/s max--not *too* much.

Besides, I've already shown that my -VM can do that res, so I suspect it's something else that's stopping him.

 

[Peter]

Now, you would have 1600x1200x4x85 bytes (at 85 Hz) = 650 MB/s potential consumption by the graphics card - just for producing the image 85 times per second. You got (realistically spoken) a total bandwidth of 1.5 GB/s (the 2100 is merely theoretical). With the CPU and GPU also needing some (for computing in general, and for altering the image when stuff gets displayes), it's somewhat reasonable that NF220 limits you to 16 bit here.

 

[Pete]

True, but I'd imagine the card uses a lot more in 3D games. And our numbers are assuming the video card just dumbly updates the whole desktop every time--I figure there must be some bandwidth-saving techniques out by now, no?

But, again, I have the same MB and it's doing 16x12x32b @ 60Hz (monitor limit) right now. I can't find a large pic of a color gradient, but this one looks right at that res.

(BTW, I forgot to mention the .768GB/s I mentioned above was for 100Hz.)

 

[Peter]

No bandwidth saving here. Remember we're still on a type of video signal here. In every single frame, every single pixel needs to be read from the frame buffer, pumped through the RAMDAC and out the signal cable.

The only ones who implemented a bandwidth saving compressed scanline storage were Cyrix in their MediaGX series integrated CPU/chipset/graphics thingies that are still popular in embedded systems.

Not transmitting every pixel every frame would require storage in the display device, and a digital datapath into it. This is being thought of for large TFT panels, and it is actually being done already in USB connected display panels.

 

[yhelothar]

go to advanced settings in display settings, then click on the monitor tab, and uncheck "Hide modes that this monitor cannot display".. if that doesn't work..

try changing your monitor driver to.. plug and play monitor..