I'm a screen real-estate addict. I can never get enough of it. I've always run my monitor fonts small, attempting to get the maximum information bandwidth from my display. The IBM T221 monitor, at 204 DPI, could either be a dream come true or an expensive mistake. Which would it be?

While this question flicked back and forth in my mind, I looked at the price tag a few times for all the unit and card required to make this setup work, and gave up with a sigh. Too expensive. But then my 21" Viewsonic bit the farm. 1880x1440 of lovely pixels in the can. I tried to makeshift, but it didn't work. Time to get serious about a new display.

In the weeks that followed, I set up a automatic search on ebay to send me information about new listings. After getting a feel for used prices, I almost bought a refurbished T221 with a one-year warrantee for $2,500. Then I found a brand new unit through Froogle for $3,000 with a three-year warrantee. The choice seemed clear since I could barely purchase additional aftermarket warrantee for the refurb unit for the difference in price.

The last question I had was about the difference between the model numbers: 9503-DG1, 9503-DG3, or 9503-DG5. Well, that got solved quick, Froogle only had one company selling the unit for less than $5,000, and that unit was a DG3. I took a chance on getting a DG3.

The differences between the units appear to be cabling only. My DG3 manual describes the DG1 cable as "for Matrox" and shows two cables that are single-ended on each end (presumably dual-link DVI). The DG3 has two cables that are double-ended on one end; two single-link DVI that merge into a large connector on the monitor for each cable. The DG5 comes with a converter box and some unknown combination of cables. I do not know what is different inside the display itself, if anything.

Understand that these monitors are nothing if you can't drive them. And getting an idea of what is necessary to drive this monitor is almost more difficult than deciding whether to buy one in the first place. You'll hear everything from "the Mac can drive the monitor at full resolution out of the box" to needing a $2,500 video card to drive it. Both are true. The only distinction is in the refresh rate. Any recent video card that has enough video memory to support 3840x2400 will likely be able to support it.

An overview of DVI standards is here. As I mentioned the T221 has four single-link inputs on two connectors. A DVI link channel can run signals up to 165MHz in any layout that the card is capable of. This bandwidth has some basic math about it that you can Google for, but suffice it to say that this bandwidth cannot move enough data to refresh 3840x2400 at 24bpp more than about 12 times per second.

The best way I can describe 12Hz refresh is something that feels like a laptop from 1990. You think it should be working faster, and in fact it does seem to be working pretty fast on your data, but the mouse and keyboard are not responding in the way you are used to your desktop machine responding. It's a bit deceptive, because the refresh on an LCD is not inversely proportional to flicker. An LCD at 12Hz with no screen motion is indistinguishable from the same screen running at five times the refresh. So yes, it's true that a T221 will work with a Mac, out of the box, but the slow refresh will drive you a little crazy.

So getting a good video card is a must. After a lot of research, I zeroed in on the NVIDIA FX2000, which was available for about 1/3 of list on eBay. This is an OEM card that is roughly equivalent to the FX3000 with less memory and a slightly slower clock speed. The card has supported drivers for Linux and Windows (lack of either being a definite dealbreaker for me...) The card has two outputs - one dual link, and a second single link. It works well, and the display software is really nice. But the cincher was that was supposed to be able to drive a T221 at better than 40Hz.

In the end, the purchase process went smoothly. The monitor arrived by UPS ground within 48 hours of ordering, but this card has a loose connection and they are now on backorder with the manufacturer. The seller assures me that I should get a replacement any day now.

So the card is partially functional, but at full 3840x2400, the right half of the screen has a very severe discoloring. It is legible and testable though. A screen shot is here (but you can’t see the discoloration in this shot because the discoloration is a hardware problem, not software...)

Out of the box with two of the four single-link cables connected to the card, I was able to get 20Hz refresh. I couldn't get more than that out of the card though. I lamented that with only one dual link port, I couldn't understand how I would be able to get the apparently necessary four outputs necessary to drive the full screen to 40Hz.

In research, I found that the DG5 is different from the DG3 because of the cabling, the DG5 providing a converter (IBM replacement part FRU 13M3200) that somehow is required for a dual-link output to go into a dual link input on the monitor (or something like that). Did the DG5 come with two of these? How is it that my card/monitor could be upgraded to work?

Well, tonight the answer came together on this. On this post, wjchan records his experience with his DG5 and a NVIDIA FX 3000. He writes:

A dual-link cannot be split into 2 single-links to drive 2 monitors. The reason is that, with dual-link, the pixel data is divided into even and odd portions and transmitted on separate links.

The latest revision of T221, the DG5, comes with an external box that splits a dual-link into two single-links. These 2 single-links contain even and odd pixels separately and cannot be used to drive other monitors. The T221DG5 recombines these 2 streams internally. Using the Quadro FX 3000, which has 1 dual-link and 1 single-link ports, one should connect the dual-link port to the external box which then connects to DVI 1&2 on the monitor. The single-link port on the QFX3K should be connected to DVI 3 on the monitor, leaving DVI 4 unconnected. The dual-link is responsible for the 2624x2400 portion of the screen and the single-link is responsible for the remaining 1216x2400 portion. This hack is necessary because the dual-link effective bandwidth of 330MHz is not enough to drive the monitor at 3840x2400@48Hz.

So it seems that the required configuration for this card, with a total of three links, is through the DG5 converter box. A converter box is available as a spare from IBM, but the latest firmware is required for them to work together. Will the latest firmware work on my DG3? It would seem that we have everything if so!

Please note about the firmware upgrade: I didn't help design this monitor, and I don't know what could happen. The manual essentially says “do not connect the USB of the monitor to the computer or it might be damaged”. I suggest that you heed that warning.

I sense this upgrader can push more than just one image of the firmware. The first time I flashed it, I left the settings alone and everything worked without noticable difference. There was no change in the refresh of the monitor. My video card still saw it as capable of only 20Hz, and the monitor only reported it was running at 20Hz. So I took a chance on selecting 25Hz. I was a little fearful, but nothing ventured, nothing gained. This was successful as well, and after rebooting the machine, the monitor reported running at 25Hz!

So it now appears that the only last step involved is to procure a converter box. That should provide access to the second link of the first connector and allow me to get the unit up above 40Hz. I'll report back here after I get some indication of success with that.

I haven't had this much fun experimenting with hardware in a while, but I was definitely uneasy about the purchase to start with. Today, if I had to do it again, I definitely would. It's a very versatile monitor. I typically run by day it at max resolution, and by night, reconfigure it to 1920x1200. This is basically uses a 2x2 square of native screen for every image pixel and is a more standard resolution at about 100dpi (good for tired eyes!)