Have I reached a hardware limit?

[Randy Simons]

Color depth is of no influence on the refreshrate the monitor can handle. If it can do 85Hz in 16 bit, it would be able to do 85Hz in 128MByte color depth

In 1280x1024 I also cannot tell the difference without an objective benchmark, but scrolling in 1600x1200 the difference is visible to me.

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Randy Simons
Digital Dreams Software
http://www.dgdr.com/

[Rags]

Not true, some cards have higher frequencies available at high resolution for 16 bit than 32bit.

Rags

[Agent31]

Thanks for the natter guys, I've learnt a bit about colour depths so far!

Yes, I am running Windows 2000 RC2 build 2128 (of varying flavours, ie Professional, Server, Advanced Server), and all the drivers for my system are the defaults installed by Windows 2000 simply because there are no manufacturer or 3rd party G200 drivers available at this point in time.

Yes, my monitor can do 75Hz at 1600x1200, that's its limit, and I was hoping to reach it (3dsmax is much more enjoyable at a higher resolution as I'm sure any regular user will appreciate). If I'm at the limit on this card though I will be a tad disappointed, it's so nice in every other respect (forgetting the gaming aspect for a minute, coz yes I still have gripes with that).

One odd thing I have noticed in Win2K is a 15bit colour depth... what's up with that?

Oh yeah, while I'm here, the OpenGL that ships with Win2K seems to work fine in an application like 3dsmax but when I try and fire up Quake3, kaboom, "blah blah OpenGL subsystem failed blah blah"... wierd? I think so!

[Randy Simons]

rags: you said it, for cards it indeed does matter, but for monitors it doesn't.

More colors -> more data to be transferred, but since the monitor-signal is analogue, there is no "transferrate" involved...

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Randy Simons
Digital Dreams Software
http://www.dgdr.com/

[ChipHead]

Hi All,

A word on 24 bit colour modes (just in case anyone's interested!).

24 bpp modes are usually "packed pixel" modes, where the first three 8 bit 'words' contain RGB values (8 bits each) and the 4th 8 bit word contains the 8 bits of the next pixels red value, so it goes

RGBRGBRGB.

Since the data is moved around in 32 bit chunks, the starting point for each pixel moves progressively one byte further into the 32 bit word, so there are four pixel descriptions in each 3 words of 32 bits each. Make sense?

A 32 bit colour mode is more like

RGBARGBARGBA where the "A" values are "don't care" values because they aren't used. This means that in 24 bpp you have the same number of colours as is 32 bpp, but there is an overhead as you need to 'unpack' the red green and blue values, since each pixel's colour values can potentially be spread across more than one 32 bit data word (i.e. the Red value isn't necessarily the first byte of each 32 bit word). In 32 bpp, you describe 3 pixels in every 3 words of 32 bits. It could then be said that 24 bpp packed pixel modes are 25% more efficient in terms of memory usage.

Packed pixel modes allow "bigger" modes to be displayed from the same size frame buffer, but they aren't usually faster. In these days of 16 or 32 MB memory configurations it's not really an issue, but it made a big difference on a 2MB VGA card! (Remember those???).

Hope this helps,

Regards,

Glenn.

[ChipHead]

One more thing...

and this time I'll try to answer the original question!

In 1600*1200 @ 32 bpp, the G200 is not limited by the RAMDAC speed, but by the memory bandwidth. This is why the maximum refresh is 65Hz. In other words, yes, you have reached a hardware limitation.

hope this helps,

Glenn.

[Agent31]

cool! thanks ChipHead, finally an answer to my question =)

PaulCS, my monitor can do 75Hz at that res, I know coz my Voodoo3 did it without breaking a sweat.

640x480 - 160Hz
800x600 - 140Hz
1024x768 - 115Hz
1280x1024 - 85Hz
1600x1200 - 75Hz

OK, anyone wanting to sell their G400's yet? bah, what a stupid question, I'd be lucky to find one on a shelf, let along second hand

[This message has been edited by Agent31 (edited 09 November 1999).]