External Monitor Resolution Question:2048x1536 or 1600x1200?

[Paul Comeaux]

Hi! I'm new to this forum.

I have a Thinkpad T42 with an ATI Mobility Radeon 7500. I would like to purchase an external monitor for use at work. I'm looking at the Dell 24 inch widescreen, which supports resolutions up to WUXGA, which is 1,920 x 1,200.

But I don't want to waste money on this if my Thinkpad won't drive this high of a resolution. So I looked up the ATI Mobility Radeon 7500 on ATI's website, and found the information I've posted below, and now I'm really confused. Does this card drive 2048x1536 or 1600x1200? I'm reasonably proficient with computers, but the specs below are beyond me. Any help would be appreciated.


Specs for ATI Mobility Radeon 7500:

Designed for exceptional 2D/3D/video performance and integrating 32 MB DDR memory, Mobility™ Radeon® 7500 is ideal for graphics-intense scenarios. It is pin compatible with Mobility™ Radeon® and future products, providing extended life for any motherboard design.
At-a-glance
Exceptional 2D/3D/video performance
32MB integrated video DDR memory, expandable to 64MB with external memory.
260MHz (at 1.5V) engine clock/ 183MHz memory clock
Pin compatible Mobility™ Radeon™ for easy transition without redesign leading to longer product cycles
Integrated Spread Spectrum for reduced EMI
Dual DAC for integrated, cost-effective multi-panel support
Integrated dual channel LVDS up to 85MHz per channel
* Resolutions from VGA up to QXGA (2048x1536)
DVI compliant integrated 165MHz TMDS transmitter
* Resolutions from VGA up to UXGA (1600x1200)
Integrated high-resolution TV-out (up to 1024x768)
PCI and AGP Bus

[chan_man]

I have a T41 and the 24" dell and they work fine together at 1920x1200 on the VGA output

[tecneeq]

I have a T41 and the 24" dell and they work fine together at 1920x1200 on the VGA output

DVI only up to 1600x1200.

Given that you also use the builtin display at the same time, do both displays run at 32 bpp (i mean at 1920x1200)? I think 32 mb VRAM is not enough for that.

[RonS]

DVI only up to 1600x1200.

Sorry, but that's simply not true. The DVI is single-link and will go to 1920x1200.

1920*1200*32bpp = about 9MB of memory. You have 32MB, enough to easily drive both displays with the second display over DVI. Also, 1920*1200 at 60Hz DVI display rate is 138MHz, which is easily less than the 165MHz max speed of single-link DVI.

In order to get a DVI port, you need either a Dock II or a mini Dock (which is really a port replicator). If you get the Dock II, you can put a PCI graphics card in there and drive additional 24" monitors. I've driven three 24" monitors off my T42 simultaneously.

Whenever you see specs with "VGA" mentioned, that means they're talking about the 15-pin analog connector, not DVI.

[tecneeq]

DVI only up to 1600x1200.

Sorry, but that's simply not true. The DVI is single-link and will go to 1920x1200.

From thinkwiki:

All ThinkPad port replicators and docking stations officially support a maximum resolution of 1280x1024 on the replicators/docks DVI port.

However, the thinkwiki says also that there is a configuration that supports 1920x1200:

The T42 with the ATI 9600 chip is reported to be able to drive the Dell 24" 2405FPW at 1920x1200 using DVI by using ATI Catalyst drivers for Windows.

Remember, he has a Radeon 7500. Here is the thinkwiki page:
http://thinkwiki.org/wiki/Problem_with_DVI_throughput

1920*1200*32bpp = about 9MB of memory. You have 32MB, enough to easily drive both displays with the second display over DVI.

I'm not sure about that. I have 16 MB VRAM on my T23 and can run my external display at 1024x768 with 32bpp, but only 16bpp if i switch to 1280x1024 (internal always at 32). I admit that doesn't proof anything since it's an entirely different chip. But i think it's a pretty good hint.

If your computation is everything one needs to know about VRAM it should work. My guess is that there are more things hold in the VRAM (buffers, overlays, hidden windows, cached backgrounds, cached rendered fonts, alpha channels).

I believe that your calculation is true if you only use VESA BIOS.

Also, 1920*1200 at 60Hz DVI display rate is 138MHz, which is easily less than the 165MHz max speed of single-link DVI.

Also true, but don't forget that theory and reality aren't always the same.

If you get the Dock II, you can put a PCI graphics card in there and drive additional 24" monitors.

Probably the safest option. If that's not possible i would go with 1600x1200.

I've driven three 24" monitors off my T42 simultaneously.

I would sell family members for that

[lithium726]

DVI only up to 1600x1200.

Sorry, but that's simply not true. The DVI is single-link and will go to 1920x1200.

Yes, it is. the OFFICIAL Spec of DVI states 1600x1200x32 has the max reso... you can tweak it to take care of higher resos like 1920x1200, which ATI and NV have, but you need dual link to go any higher.

I'm not sure about that. I have 16 MB VRAM on my T23 and can run my external display at 1024x768 with 32bpp, but only 16bpp if i switch to 1280x1024 (internal always at 32). I admit that doesn't proof anything since it's an entirely different chip. But i think it's a pretty good hint.

no, thats just due to the [censored]-as-hell S3 chip inside the T23.

[daeojkim]

Nowadays resolution is mostly not limited by the graphics card. They all come with so much memory that it will not have problem using those large LCD monitors for 2D displa, including 1920 x 1200.

It seems like ATI and IBM drivers do nothave option for resolution above 1600 x 1200. Again not a hardware limitation but just a setting on the software.

Try Omega drivers. I guantee that 1920 x 1200 will work on ATI 7500 through DVI.

[Paul Comeaux]

Thank you all for the responses. I am learning a lot.

Sorry to bring the discussion down to a more basic level, but can someone shed some light on these questions?

* Does "Integrated dual channel LVDS up to 85MHz per channel/Resolutions from VGA up to QXGA (2048x1536)" mean that I can simply connect the monitor directly to my Thinkpad and get 2048x1536?

* If so, is the idea that a digital connection is so much clearer that it would be better to get a Dock II and connect digitally (DVI) even though the resolution appears, from the specs, to be limited to 1600x1200? (The Dock II is $300+; but I'd consider it if digital is that much better.)

* A few responses indicate that I could get 1900x1200 from the DVI connection. How is this possible if the specs for the ATI indicate max resolution of 1600x1200? Isn't this a hardware or physical limitation of the driver?

* I check Lenovo's site, and the specs for Dock II state: "DVI pass-through port ( will support resolutions up to 1280x1024 based on attached system)." So if this is the case, then if I get the Dock II and connect through DVI, I only get 1280x1024, right? In this case, am I better off connecting directly through VGA and getting up to 2048x1536, which is more than enough to support the Dell 24 inch monitor?

* Daeojkim says, "It seems like ATI and IBM drivers do not have option for resolution above 1600 x 1200. Again not a hardware limitation but just a setting on the software." OK, help. So are you saying that even though the official spec says 1600x1200, I could tell it that my monitor is 1900x1200 and it would truly drive this, and not simply scale the 1600x1200 up to 1900x1200? Are you talking about rewriting the software for the driver?

Guys, I appreciate your help. And I bet I'm not the only one who, while I can follow the discussion, is saying, "gee, I sure would like to understand some of the more fundamental issues!"

Thanks! This is a great forum. I found it because I was looking for an answer to this specific question, but now that I'm here, I look forward to participating!

[greghead]

Two days ago my new Samsung SyncMaster 214T arrive. It's 21", 1600x1200, connected via DVI. It's gorgeous -- bright, crisp, <= 8ms.

1600x1200 on 21" is easy on the eyes, but still a lot of room to spread out.

Also, I've noticed that 1600x1200 isn't excessively greater than 1400x1050; it's doesn't cause whiplash moving back and forth. In other words, 1600x1200 is nice extra room to spread out when available, without causing me to feel too cramped when I have to work on the 1400x1050 laptop screen at home or in meetings. If that makes any sense.

[kassoe]

Just for the record:

I have with succes now set up my T42 with ATI Radeon 7500 to use both the built-in screen and a Dell 2407 widescreen monitor (I guess it'll be the same with a Dell 2405).

I downloaded the unofficial ATA driver mentioned several places in this forum - http://www.omegadrivers.net - and it installed without any problems (read the instructions carefully).

Thanks for the hints and help I found here in different threads on this this issue.

[crashnburn]

Interesting I might need to do a similar assessment for my new T42 for a Dell 21/20" Trinitron Monitor I have.

Maybe need to get a docking station of sorts.

[kassoe]

Maybe need to get a docking station of sorts.

With my setup the docking station gives me the dvi connection. On the laptop itself there is only vga. I have by now six things connected to the docking station so it would be bit of a job to connect/disconnect otherwise.

[kassoe]

Now, as posted above, I got the Dell 24" to work in dual screen mode. I have since yesterday tried several positions of the screen and unless I start using an external keyboard (which I don't want to because of space limitations) I find it too big So I'll exchange it for a 1907 (not widescreen) which will fit fine on the side.

Edit: Nope, changed my mind again. It is too nice to part with and I found a way to position the two screena with a little overlap so it works fine now.