1600x1200 @ 24 bit with Rage Mobility?

[Rage Futility]

I long for 1600x1200 with 24 bit color depth...

Well I have an old laptop (450 MHz, 1024x768 display) with a Rage Mobility P/M AGP. This adapter has 8 MB of video memory available on the card. What I want to do is to use an external LCD as part of extended desktop in Windows XP (because Microsoft decided to disable native support for extended desktop in Win2000) with the external LCD displaying at 24 bit color depth. According to my calculations this should be possible! Unfortunately the LCD reverts to 640x400 when it try it.

Using this formula:
(width in pixels) x (height in pixels) x (color bit depth)
and dividing by 8 (bits in a byte) and by 1024 the desired number of times I get:

1024x768@24bit + 1600x1200@24bit = 7.75 MB
and
1024x768@16bit + 1600x1200@24bit = 7.00 MB

both within the 8 MB available on the Rage Mobility. But it's a no go.

Still I'm able to use the displays at 1024x768@32bit + 1600x1200@16bit (6.67 MB needed). And amazingly I can disable the laptop's own display and use the external LCD as primary monitor at native resolution with 32 bit color (7.33 MB needed).

So what gives? Why can I not utilize all the video memory when using the extended desktop feature? Any settings I could try changing?

 

[Big Z]

1. Extended desktop does not work on the Rage Mobility P/M under Windows 2000/XP. You will get display cloning though. (Same image on both monitors)
2. The driver you are using is a possible limitation.
3. If the driver is not the issue, it probably comes back to how the chip processes 24 bit. It appears its done at 32 bit and then downsampled to 24 bit.

 

[Rage Futility]

Hello Big Z, thanks for your response.

1. Extended desktop does not work on the Rage Mobility P/M under Windows 2000/XP. You will get display cloning though. (Same image on both monitors)

That's not correct. I indeed have an extended desktop with 1024x768 on the laptop display and 1600x1200 on my LCD. That's with XP, which has native support for "DualView" (Microsoft's term for extended desktop). What else is needed is a display adapter with two independent display controllers and support for the "DualView" feature in the driver. The driver provided by Compaq supports this feature for the Rage Mobility on XP (at least the driver that is installed on my system). Windows 2000, on the other hand, seems to have been crippled by design by Microsoft. Have a look here for more information (scroll down to the quotes) regarding Windows 2000 and Rage Mobility, and here regarding Windows XP and Rage Mobility.

2. The driver you are using is a possible limitation.
3. If the driver is not the issue, it probably comes back to how the chip processes 24 bit. It appears its done at 32 bit and then downsampled to 24 bit.

That could possibly be the reason, sounds kind of logical. But when I searched for info about XP and native support for extended desktop I found something interesting regarding video memory. A possible explanation is suggested in the second link above:

Furthermore, this support must share the available memory on the video adapter between the monitors that are connected to the internal and external ports. For example, if the video adapter has 16 MB of available memory, the memory on the video adapter is divided such that each monitor has access to 8 MB.

I don't know if to read that literally, that is to say that the video memory will be split in two equal parts (4 MB in my case) or if he just used two monitors with the same resolution + bit depth as an example. I found no clear confirmation of this by searching the net. But I went ahead and experimented a little with different resolutions and bit depths. What I found is that both displays at 1280x1024@24bit (3.75+3.75 MB) worked but 640x480@16bit and 1280x1024@32bit (0.59+5.0 MB) did not work. This means that there is a difference in memory requirement between 24 and 32 bit depth (there goes your theory ). So I guess 4 MB is the hard limit for each display then. To me this seems like a badly engineered solution if the adapter only can split the memory in two equal halves and not allocate as required. Anyways, it doesn't look like there is a simple solution to my problem then...


Off the topic of this post (no need to start a new topic), is there a way to use the external LCD in pivot mode with the Rage Mobility? No support in the drivers it seems, and when I searched the net I could only find a software package for sale at 40$. Is there some other driver or no-cost software that can provide pivot functionality with the Rage Mobility?

 

[Big Z]

Sorry there.. i seem to have made a mistake. And my site says multimonitor is supported. Oh well.

Rotation is supported in the drivers at my site. Not sure how well it works with the external monitor though.

 

[Rage Futility]

Alright, what an experience...
1200x1600 is indeed a weird way to work with a computer, that's what I found at least. Unfortunately enabling rotation put my old laptop to a crawl, the rendering of web pages etc were painfully slow. I think dedicated hardware would be in order for this feature. I know Eizo have something like that in their displays. And you were right, rotation didn't work with extended desktop. In fact the ATI specific tabs in the display settings disappeared with extended desktop enabled and this new driver on my system.

What is worse is that both my windows installations experienced problems with the drivers I found at that web page. I suspect it is related to the rotation functionality or the high resolution used. What happened is that I disabled the laptop screen to run full resolution on the LCD and then I just shut the computer down when done, without setting it back. When I restarted major problems occured. With XP the driver stopped working, but vga mode worked. In Win2000 I could boot to desktop and then it would bluescreen. Over and over. I thought I would loose that installation for a while. After a couple of days I found that it was some alteration to the 'system' registry hive that were the cause of the crashes. I replaced it with a very old backup, and so far most things seem to work properly. Thank heaven for dual boot! Without that I would probably have lost quite a bit of data. Oh well, I think it's safe to say...

I will not play with rotation on my laptop again
I will not play with rotation on my laptop again
I will not play with rotation on my laptop again