If you want dual-digital on a stock-standard AGP card for OS 9, these are your options to the best of my knowledge:
- GeForce 4MX 32MB ADC/DVI (OEM Apple)
- Radeon 9000 Pro 64MB ADC/DVI (OEM Apple)
- Radeon 9000 Pro Mac Edition 128MB ADC/DVI (Retail)
- GeForce 4 Ti4600 128 MB ADC/DVI (OEM Apple)
Power consumption should not be an issue if you are not using an ADC monitor powered directly from the ADC port. If you do have an ADC monitor it is quite widely advised to get an external DVI-to-ADC converter box with its own dedicated power supply. You would have to get an ADC-to-DVI adapter also to put first in the chain, but you'll need that no matter what you are doing with these cards and dual monitors. (I actually own a two-input switch box with DVI inputs and ADC output with dedicated ADC power supply which simplified the chain to the primary monitor and let me connect a second computer at the same desk.)
This evening I tested a dual-monitor/dual-digital 1920x1080 configuration on the GeForce 4MX 32MB, Radeon 9000 Pro 64MB and GeForce 4 Ti4600 128MB. (I just got the Ti4600 in a couple days ago from eBay so I was quite interested to see the results of this test.) One monitor was connected ADC-to-DVI, and the second monitor (an LCD TV) DVI-to-HDMI. The test-bed computer was an MDD FW800 running Mac OS 9.2.2 with the last known ATI and Nvidia drivers. On all three cards, both screens came up immediately in their native 1920x1080 modes automatically with all alternate resolution settings available.
GeForce 4MX 32MB cards should be fairly easy to find on eBay. If you want to find all the listings properly you will have to use the Apple part numbers in the search, 603-1263 or 630-4023, because many of the sellers don't know the name of these otherwise unmarked OEM cards.
Radeon 9000 Pro 64MB cards are available on eBay right now for a reasonable amount of money. (I just recently bought a second one myself.) If you want to find all the listings properly you will have to use the Apple part numbers in the search, 603-3352 or 630-4845, because many of the sellers don't know the name of these otherwise unmarked OEM cards.
Radeon 9000 Pro Mac Edition 128MB cards are going to be a rarity in re-sale these days. At the moment there's a listing on eBay featuring the full package from what probably was one, but inside it has an old Rage128 card. I warned the seller about that but he never took down or modified the listing.
There was someone recently selling a bunch of GeForce 4 Ti4600s for $100 US a piece if I remember correctly. I refused to pay that much but they all sold anyway. My patience paid off and I later found a listing in my home country of Canada for much less. They don't come up for sale very often, but so many sellers know the collectable nature of these cards that they eventually get listed here and there.
Additional information regarding GeForce 4MX:
- GeForce 4MX 32MB ADC/DVI (OEM Apple)
- GeForce 4MX 64MB ADC/DVI (OEM Apple)
In my experience there are two different versions of the GeForce 4MX, only one of which fully supports OS 9. The first one is 32MB and has pin-based RAM chips - this fully supports OS 9. The second is 64MB and has ball-grid RAM chips - VGA will get stuck at 640x480, while DVI or ADC will lock to a single higher resolution in OS 9. To what extent specific ROM revisions might change this, I can't say for sure.
During my testing of the 64MB variant of the card the digital output did correctly detect and display on the monitor at the maximum/native 1920x1080 mode. The TV would actually detect correctly but would never display video - I confirmed this by moving the connection over to the monitor after boot. (Probably related to incorrect HDCP handshake handling.) The most important discovery though is that oddly this card appears to only have a single digital display driver IC, meaning you can't actually use the two digital outputs simultaneously. It will show a second screen when adapted to VGA but locked to 640x480 only as mentioned above. As I recall, the resolutions don't get locked/limited under OS X, so the ROM is not 100% compatible with OS 9. That said, the deal-breaker is the apparent lack of a second digital driver IC.
