I connect that TV to computers via the VGA port. But I've also pulled down a 1920x1080 LCD panel with DVI and tried that too. You guys do realize that the system IS NOT POST-ING with this card in it. It's not about the monitor plugged in. The system never even gets to a beep code. I've had more success with a bad memory stick installed. At least THEN I got beep codes telling me there was a problem.

I was asking, because I know that with my X800/X850 AGP cards (although without Rialto bridge chip), when connected via DVI->HDMI adapter to HDMI monitor/TV, machine will not post either. Well, more specifically, monitor will stay in stand-by, and will show nothing, no matter what you do. When you connect it via DVI directly, it's ok. I need to do more testing with VGA. But with my 9500, no such problem, no matter how I will connect it (VGA, DVI, HDMI, you name it). And it's not problem with motherboard, I have confirmed that by friend, that this is actual behavior on other systems too.

Well, I've been reading sites and watching informative videos, coupled with the evidence being given to me by my system...and I've really come to three conclusions.
1. The PCIE-AGP bridge is AGP 8x only and locking up MB during POST.
2. The x700 is pulling too many watts and the MB is refusing to POST with the available Amps on the 5V rail of the PSU.
3. The x700 card is somehow dead and locking up the system, preventing POST.

Now I've tried powering everything on at 25 Amps by removing the DVD-ROM, ZIP, and Hard Drives to reduce power draw. I'm wondering if the Barton core is pulling more watts than my Palomino core did. I'm wondering if putting the Palomino back in will reduce current draw and get the system to POST with the updated card installed, just to see what happens. I'm also going to pull one of the 1GB RAM sticks out, dropping the system to only 1 memory stick. Might help with power draws. I kinda wish I had one of those 45 Amp PSUs to try on this system. That would at least rule out #2 if it still refuses to POST. I also don't believe #3, because even if the video card is bad, I'd usually get a Beep Code from the MB during POST, saying no VGA installed. I'm going to be going through all the hardware I have available to see if I have ANY PSU with more than 30A on the 5V rail today.

EDIT: Ok, so I tried everything out of the system, including the RAM, so it was just MB, CPU, and x700 card. At least I got a beep code this time - the NO-RAM beep code. Put one stick back in, no response. In fact, I'm noticing that the x700's fan doesn't immediately start up at full-speed. It turns on and off, almost like the card simply doesn't have the juice to fully start-up. That's with the 25A 500-watt PSU.

I broke apart my Pentium III Voodoo2 SLI system and it has an older Pentium 4 ready 350Watt PSU with 30A on the 5V rail. I used THAT...same story.

I pulled out my old 1800+ Palomino CPU and swapped the CPUs out and reset the CMOS. Same shit. So I'm going to assume at this point that the x700 is simply not receiving enough power and that MAYBE you're right, but I don't have anything with more power than 30A on the 5V line. Just putting in the 9550 back in and the system fully POSTs and starts up into Windows XP (when the HDD is connected, of course).

So if it's a power-draw issue, wouldn't the 9800 Pro pull just as many watts, if not more? Wouldn't it also not start if I got one? What about a new PSU? Newegg has a Logisys for under $20 that's 550 Watts, but has a whopping 38A on the 5V rail.
https://www.newegg.com/Product/Product.aspx?I … N82E16817170019

Hmm, my PSU have 400W with 23A on 5V rail, and can powered C2Q 6600, with Radeon X850. I just can't see, that your PSU would be so weak, that it would have that much of problem with X700 just because of shortage of power.

Unfortunately, I don't have any ATI card with Rialto chip for testing, since as I mentioned previously, X800/X850 are native AGP cards.

Nah mate, the problem is that it's an AMD Athlon XP system. Let me point you to a Phil's Computer Lab video:
https://www.youtube.com/watch?v=efK7mw8eYiE

Your Core 2 Quad pulls all its power from the 12V rail, not the 5V rail. Modern PSUs have very powerful 12V rails. But around 2002-2003, PSUs had bigger 5V rails. The thing about the Athlon XP is that SOMETIMES if you run out of power, the system would refuse to boot - as mine does with the x700 installed. It boots perfectly fine with the 9550xl installed. And I know that the system has a beep code during POST for no video card installed and I'm not getting that with the card in - just the same no-boot that you see in Phil's video linked above.

I used to have an Aopen 250w PSU in my Athlon system that has a 25A +5v rail, and at one point remember trying a 9800xt in it, it didn't
post. That was with a Palomino mobile cpu at 1250mhz.
Years later I found out, as previously mentioned, that same motherboard works with just about anything I have tried in it, up to HD3650, 7800GS, X850XT,
as long as a powerful enough PSU is used.