which AGP graphics Card to Buy

Thanks BD, you are right on both counts. I fixed the monitor so it only looks for itself. And I did find my original G5 install disc. It started to load AHT, but then failed. According to the included readme, this may have happened because I have the 6800 video card installed, rather than the original card. I'm not ready to pull it out quite yet and reinstall my original card, which may also mean that I'm not quite committed enough to fix the freeze problem by ripping out hardware inside my mac.

Nonetheless, the timing of the video card's installation, and the daily freeze are close enough to make me still suspect that the video card's ROM is somehow involved in the freezes. So doing an AHT without the 6800 video card may show me nothing.

The AHT did display one little piece of info before dying on me:

invalid memory access at:
&SRR0 : 00000000.00000000
&SRRO : 10000000.00083030

any idea on what this means and how to make it "valid" again? My system profile informs me that all of my 5.5 gb of memory is working OK. So to be precise, it's probably not the memory itself, but access to the memory. If no one can advise me here, I'll next try Apple tech support.

I conclude that there is something in the flashed ROM of the 6800 card that causes my G5 to freeze on start up. As i have explained, if i press the start button until the machine turns off, then the second time, the computer starts up just fine. My own guess is that it boots OK the second time because the problem is the result of some routine a mac runs when you shut it down via "shut down" in the Apple menu.

This same article also describes a solution one user discovered by entering some UNIX code via terminal. Unfortunately, the solution I read is written for other terminal users, which is beyond my own computer expertise. So unless i can get someone here to explain it in plain language, i may just keep booting twice. If that becomes a pain, i may go back to my old video card.

Hopefully,my own experience will help guide other folks considering a 6800 "upgrade". I also believe that it doesn't happen with every G5. It's a gamble.

The above message is not complete. Here's what I meant to say:

I did test the DIMMs, using Rember. All 5 gig passed with flying colors. I have also just read an article on the C/Net board. It describes my problem to a T. You can read it for yourself here:

http://reviews.cnet.com/8301-13727_7-10334517-263.html?tag=mncol

I conclude that there is something in the flashed ROM of the 6800 card that causes my G5 to freeze on start up. As i have explained, if i press the start button until the machine turns off, then the second time, the computer starts up just fine. My own guess is that it boots OK the second time because the problem is the result of some routine a mac runs when you shut it down via "shut down" in the Apple menu.

This same article also describes a solution one user discovered by entering some UNIX code via terminal. Unfortunately, the solution I read is written for other terminal users, which is beyond my own computer expertise. So unless i can get someone here to explain it in plain language, i may just keep booting twice. If that becomes a pain, i may go back to my old video card.

Hopefully,my own experience will help guide other folks considering a 6800 "upgrade". I also believe that it doesn't happen with every G5. It's a gamble.

http://reviews.cnet.com/8301-13727_7-10334517-263.html?tag=mncol

In this article, the computer is a server, but the problem is practically identical to my own problem. In this article, the guy had a driver for his 6800. Mine came without a driver and apparently, the EBay seller didn't think it was necessary. Since it worked out of the box, I assumed he was right. Since he had flashed the card using some commonly available code, i assume that that code has a flaw which this article points out, and which likewise shows up in my use of the card.

as the article that you link to, mentions, apple supplies the drivers to these cards, not NVidia. Not only that, but ALL these 6800 cards that are being sold on EBay were made for PCs, and flashed aftermarket by the sellers themselves, to make them accessible to a mac. There are 5 or 6 of these sellers, and if you visit EBay and do a search on mac 6800 or mac 7800 you'll find all of them.

Before i bought mine, I spent some time on this mac discussion group, asking questions in advance to discover if other folks were satsified with their own card upgrade, of if they had any problems in buying them. One guy in particular in this discussion group, , Japanmac, seemed quite knowledgeable about the entire subject of flashing a PC video card to make it work on a mac, and he answered all my questions and ultimately promoted the value of upgrading.

Also, I strongly suspected that I really needed to upgrade my card, since i had just bought a 24 inch NEC monitor, and the old bundled card was laboring to keep up with the large screen.

One new detail has emerged regarding my freeze problem. I have now discovered that if i don't turn on my monitor while booting, the G5 will not freeze, but will load until everything s loaded OK. But then once everything is loaded, and i turn on my monitor, the computer will freeze within about a minute. So I am convinced that the problem has to do with monitor.

thanks guys. i do appreciate your attention.
Here's what i found:

My card is a BFG geforce 6800GT, The ROM is: 2120m. It is Nvidia (0x10de), it has 256k mb videoram.

It was the second card the vendor sent me. The wiring of the first card fried inside my G5 after just 2 days. The current card uses two connectors, which i installed using 2 splitters.

The display resolution is 1920 x 1200 at 60hz. I don't know the answer to your question regarding native resolution. It is an NEC 24 inch flat screen, 2490wuxi2.

Below i have included the windowserver log of today's dual attempt to start up the machine. I'm not sure what it all means, since I've never used Console before. Hope you can tell me:

Jul 19 09:15:54 [61] Server is starting up
Jul 19 09:16:01 [61] CGXMappedDisplayStart: Unit 0: boot screen
Jul 19 09:16:03 [61] CGXMappedDisplayStart: Unit 0: no display alias property
Jul 19 09:16:03 [61] CGXMappedDisplayStart: Unit 1: no display alias property
Jul 19 09:16:05 [61] AGCAttach: Couldn't find any matches
Jul 19 09:16:05 [61] CGXPerformInitialDisplayConfiguration
Jul 19 09:16:05 [61] Display 0x28d9e300: MappedDisplay Unit 0; Vendor 0x38a3 Model 0x678c S/N 0; online enabled (0,0)[1920 x 1200], base addr 0x1800000
Jul 19 09:16:05 [61] Display 0x3f003d: MappedDisplay Unit 1; Vendor 0xffffffff Model 0xffffffff S/N -1; offline enabled (2944,0)[1 x 1], base addr 0x1800000
Jul 19 09:16:18 [61] GLCompositor: GL renderer id 0x00022404, GL mask 0x00000003, accelerator 0x0000282f, unit 0, caps 0x00000003, vram 256 MB
Jul 19 09:16:18 [61] GLCompositor: GL renderer id 0x00022404, GL mask 0x00000003, texture units 4, texture max 4096, viewport max {4096, 4096} extensions 0x0000000f
Jul 19 09:17:26 [61] kCGErrorFailure: CGXDisableUpdate: UI updates were forcibly disabled by application "Entourage" for over 1 second. Server has re-enabled them.
Jul 19 09:17:26 [61] kCGErrorFailure: Set a breakpoint at CGErrorBreakpoint() to catch errors as they are returned
Jul 19 09:33:03 [61] kCGErrorIllegalArgument: CGXGetWindowWorkspace: invalid window id: 47
Jul 19 09:33:10 [61] kCGErrorIllegalArgument: CGXGetWindowWorkspace: invalid window id: 4b
Jul 19 09:33:18 [61] kCGErrorIllegalArgument: CGXGetWindowWorkspace: invalid window id: 4f
Jul 19 09:34:44 [61] kCGErrorIllegalArgument: CGXGetWindowWorkspace: invalid window id: 53
Jul 19 09:54:50 [61] kCGErrorIllegalArgument: CGXGetWindowShape: Invalid window 58
Jul 19 09:54:50 [61] kCGErrorIllegalArgument: CGXGetWindowShape: Invalid window 58
Jul 19 09:54:50 [61] kCGErrorIllegalArgument: CGXGetWindowShape: Invalid window 58