I've been lurking for far too long...so here goes my first post!
So I've read through the whole of Cindori's thread titled "Ultimate Thread: 4890 in Mac Pro", trying to figure out exactly which Radeon 4890 would be a compatible and reliable solution for flashing to work on Snow Leopard 10.6.1, Mac Pro 1,1.
To my disappointment, I'm more confused now than I was when I first started reading the thread.
Why? Because cards have gone through revisions and what was working then, now no longer works or has problems. Example: Sapphire cards seem to be what to look for since that was what Cindori used, but "newer" Sapphire cards, even though they may look like reference cards, don't seem to work; older XFX cards worked (and only ZDFC from what I understand), but newer revisions no longer work, etc, etc.
So I thought I would start a thread where we could compile a list of confirmed working cards for those of us wishing to enter the realm of flashed PC cards in our Macs.
By the way, thanks to Cindori, nektas et al for all the delicious information on getting a great card into a Mac Pro without the price gouging from
!! 
A quick recap for those too lazy (or without enough time) to read through that entire thread (please correct me if I misunderstood or have provided incorrect information, thanks):
1) Flashing will only work on REFERENCE CARDS (and only some reference cards for that matter), NOT overclocked or modified cards (NOTE: This may no longer be true, see "confirmed working" below).
2) Dual DVI seems to work fine under Snowy (10.6.1), but your mileage may vary on older versions of Leopard depending on the card you are using.
3) Older versions of Sapphire and XFX seem to work, but newer revisions are being problematic. I read one instance of success with an HIS card...Diamond did not seem to work for that person (so he tried a HIS and it worked).
Again, there are different models out there and different revisions, but I am unsure which exactly have been confirmed working (thus why I want to start compiling a list here).
So, to start, here are some things I found...
What a reference ATI Radeon 4890 looks like without the cooling (taken from http://ixbtlabs.com/articles3/video/rv790-2-p1.html):
FRONT

BACK

And Cindori's card (with cooler):

In order for this list to be comprehensive, please provide the following information if possible.
Maker: Sapphire, XFX, HIS, etc
Model#: HD-489A-ZDFC, 100269HDMI, etc
Full Product Name: SAPPHIRE 100269HDMI Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
Item #: N82E16814102852, N82E16814150359, etc
Core Clock: 850MHz, 880MHz, 900MHz, etc
Memory Clock: 900MHz, 950MHz, 975MHz, etc
Output: 2 DVIs and 1 S-Video, 1 DVI and 1 HDMI, etc
Link:
Any other identifying information that would help someone looking to get (or avoid) a card, such as PICTURES, PART #, REVISION #, or anything else you may think of.
--------------------------------------------------------------------------------
Updated: 11/27/09
CONFIRMED WORKING
1) Sapphire Radeon 1GB (normal model, not overclock or such)
ATI RADEON HD4890 1G GDDR5 PCI-E DUAL DVI/TVO
SKU#: 21150-00
P/N 102-B79002-00-AT
--Cindori: Original post here.
1a) Sapphire NEW EDITION
Success reported but with a few caveats. READ THIS POST BEFORE BUYING! (thanks mfka for the writeup and Peloche for the ROM and others who contributed). Only tested and confirmed working for Qimonda chipset. Read the post to find out more. Seems that Hynix chipset also works.
Success reported here.
2) POWERCOLOR PLUS AX4890 1GBD5-UH Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 CrossFire Supported Video Card - OC Edition - Retail Link (deactivated...again)
--Tutor: Works under SL flashed
--SuperSpiker: Success reported here.
3) MSI R4890-T2D1G OC Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - OC Edition - Retail Link (discontinued)
--Success reported here and here.
4) XFX Black Edition
Success was reported here
Note: Requires modified ROM to remove screen shakes
5) XFX ZDFC
Success was reported here
But also a Fail report here
(the power was not the issue)
6) Sapphire HD 4890 Toxic Vapor-X OC 1 gb (Actually a Sapphire TOXIC with Vapor-X cooling)
Success reported here.
7) HIS H489F1GP Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail Link. (Deactivated/Discontinued on Newegg...check back often as it seems to come back into stock every once in a while)
Success reported here, here, and here. Also here (issues with tearing on 30" when two monitors hooked up...anyone else with this issue?) and here. And yet another success here.
Both red PCB (with 6 and 6 pin power) and blue PCB (with 8 and 6 power) cards have been confirmed working.
In case you need it, here is the stock (original) ROM (thanks Treksdot)
8) XFX Radeon 4890 1.0 GB DDR5 XXX (HD-489A-ZDDC)
Success reported here. (Used injector method) and here (flashed with ATI Tool)
9) XFX 489A-ZDF7 stock
Success reported here.
"used the overclock package...not good results, the fan was running hard at ALL TIMES and was very loud...
I reverted to the normal package... SILENCE almost as if using the stock card, the fan runs great during game play."
DOES NOT WORK
1)No overclocked or modified cards have been reported to work fully . One report of Powercolor OC Edition working (see #2 above, Tutor and SuperStriker) as well as an MSI T2D1G-OC (see Rominator #3 above)
There was one instance of a XFX TOXIC card working but with problems (see #6 above).
2) Vapor-X OC
Failure reported here
3) Diamond 4890 (A4890PE51G)
Failure reported here.
4) Newer versions of XFX ZDFC
Failure reported here, here and many other places.
Other Resources:
http://macprogpu.wikidot.com/aticards Thanks peskaa!
QE CI Exotic Package 10.6.2 - Thanks Netkas!
--------------------------------------------------------------------------------------
And finally, a little disclaimer: I AM NOT RESPONSIBLE FOR ANY DAMAGE TO YOUR MAC, YOUR WALLET, YOUR HOUSE, YOURSELF, OR ANYTHING OTHER THAN MYSELF. I'm only trying to compile a list to help out those looking for a compatible card, but I cannot guarantee these findings or that they will work for YOU. Thanks, please come again
So I've read through the whole of Cindori's thread titled "Ultimate Thread: 4890 in Mac Pro", trying to figure out exactly which Radeon 4890 would be a compatible and reliable solution for flashing to work on Snow Leopard 10.6.1, Mac Pro 1,1.
To my disappointment, I'm more confused now than I was when I first started reading the thread.
So I thought I would start a thread where we could compile a list of confirmed working cards for those of us wishing to enter the realm of flashed PC cards in our Macs.
By the way, thanks to Cindori, nektas et al for all the delicious information on getting a great card into a Mac Pro without the price gouging from

A quick recap for those too lazy (or without enough time) to read through that entire thread (please correct me if I misunderstood or have provided incorrect information, thanks):
1) Flashing will only work on REFERENCE CARDS (and only some reference cards for that matter), NOT overclocked or modified cards (NOTE: This may no longer be true, see "confirmed working" below).
2) Dual DVI seems to work fine under Snowy (10.6.1), but your mileage may vary on older versions of Leopard depending on the card you are using.
3) Older versions of Sapphire and XFX seem to work, but newer revisions are being problematic. I read one instance of success with an HIS card...Diamond did not seem to work for that person (so he tried a HIS and it worked).
Again, there are different models out there and different revisions, but I am unsure which exactly have been confirmed working (thus why I want to start compiling a list here).
So, to start, here are some things I found...
What a reference ATI Radeon 4890 looks like without the cooling (taken from http://ixbtlabs.com/articles3/video/rv790-2-p1.html):
FRONT

BACK

And Cindori's card (with cooler):

In order for this list to be comprehensive, please provide the following information if possible.
Maker: Sapphire, XFX, HIS, etc
Model#: HD-489A-ZDFC, 100269HDMI, etc
Full Product Name: SAPPHIRE 100269HDMI Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
Item #: N82E16814102852, N82E16814150359, etc
Core Clock: 850MHz, 880MHz, 900MHz, etc
Memory Clock: 900MHz, 950MHz, 975MHz, etc
Output: 2 DVIs and 1 S-Video, 1 DVI and 1 HDMI, etc
Link:
Any other identifying information that would help someone looking to get (or avoid) a card, such as PICTURES, PART #, REVISION #, or anything else you may think of.
--------------------------------------------------------------------------------
Updated: 11/27/09
CONFIRMED WORKING
1) Sapphire Radeon 1GB (normal model, not overclock or such)
ATI RADEON HD4890 1G GDDR5 PCI-E DUAL DVI/TVO
SKU#: 21150-00
P/N 102-B79002-00-AT
--Cindori: Original post here.
1a) Sapphire NEW EDITION
Success reported but with a few caveats. READ THIS POST BEFORE BUYING! (thanks mfka for the writeup and Peloche for the ROM and others who contributed). Only tested and confirmed working for Qimonda chipset. Read the post to find out more. Seems that Hynix chipset also works.
Success reported here.
2) POWERCOLOR PLUS AX4890 1GBD5-UH Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 CrossFire Supported Video Card - OC Edition - Retail Link (deactivated...again)
--Tutor: Works under SL flashed
--SuperSpiker: Success reported here.
3) MSI R4890-T2D1G OC Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - OC Edition - Retail Link (discontinued)
--Success reported here and here.
4) XFX Black Edition
Success was reported here
Note: Requires modified ROM to remove screen shakes
5) XFX ZDFC
Success was reported here
But also a Fail report here
(the power was not the issue)
6) Sapphire HD 4890 Toxic Vapor-X OC 1 gb (Actually a Sapphire TOXIC with Vapor-X cooling)
Success reported here.
7) HIS H489F1GP Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail Link. (Deactivated/Discontinued on Newegg...check back often as it seems to come back into stock every once in a while)
Success reported here, here, and here. Also here (issues with tearing on 30" when two monitors hooked up...anyone else with this issue?) and here. And yet another success here.
Both red PCB (with 6 and 6 pin power) and blue PCB (with 8 and 6 power) cards have been confirmed working.
In case you need it, here is the stock (original) ROM (thanks Treksdot)
8) XFX Radeon 4890 1.0 GB DDR5 XXX (HD-489A-ZDDC)
Success reported here. (Used injector method) and here (flashed with ATI Tool)
9) XFX 489A-ZDF7 stock
Success reported here.
"used the overclock package...not good results, the fan was running hard at ALL TIMES and was very loud...
I reverted to the normal package... SILENCE almost as if using the stock card, the fan runs great during game play."
DOES NOT WORK
1)
There was one instance of a XFX TOXIC card working but with problems (see #6 above).
2) Vapor-X OC
Failure reported here
3) Diamond 4890 (A4890PE51G)
Failure reported here.
4) Newer versions of XFX ZDFC
Failure reported here, here and many other places.
Other Resources:
http://macprogpu.wikidot.com/aticards Thanks peskaa!
QE CI Exotic Package 10.6.2 - Thanks Netkas!
--------------------------------------------------------------------------------------
And finally, a little disclaimer: I AM NOT RESPONSIBLE FOR ANY DAMAGE TO YOUR MAC, YOUR WALLET, YOUR HOUSE, YOURSELF, OR ANYTHING OTHER THAN MYSELF. I'm only trying to compile a list to help out those looking for a compatible card, but I cannot guarantee these findings or that they will work for YOU. Thanks, please come again