Current summary:
- Ethernet: working
- Audio: 2 ch from line-out: working (my SPDIF cable is on order)
- Video: nvidia 8400GS 256 with CI/QE working

1. Boot from iPC 10.5.6
2. Use Disk Utility to erase HD. Quit Disk Utility back to the Installer
3. Go to Customize and pick
- Fixes: verbose mode, start/restart
- Video: nvinject 256M (for nvidia 8400 gs) (I tried natit and nvdarwin 256M without results)
- Applications: osx86 Tools
4. Install, and wait for reboot. Note I did NOT get the nice welcome screen.. I had a grey background (looked like plain X windows does), but the normal "pick your language" dialog box was there.
5. Run OSx86 Tools, click on "View PCI Device/Vendor ID".. let it install lspci, reboot, run osx86utils and click on "View PCI info..." again, and save the report.
6. Choose "Download and install HW drivers", pick ALC883, and do a download/install, it will install
- Intel HDA 82801G (ALC883)
- Intel 82801g Series USB EHCI
- Intel ICH7 (82810GB/GR/GH) SATA
- Realtek RTL811/816BB
Click Download and Install.. you will get several dialog boxes to hit ok showing you progress
7. Go to Apple Preferences->Sound->Output and choose lineout. Change the volume and you should hear a beep (from speakers connected to the green connector on the back)

Note: I tried the ALC883 and Legacy 883 addr0 drivers in iPC with no luck.

At this point my mystery was this.. I seem to have full graphics operation via Preferences->Displays and am running at 1920x1080, BUT "About This Mac" says Core Image is "Software" and Quartz Extreme is "Not supported".

So I went and did some research.

I made a backup directory and copied all the Ge* and NV* kexts from /System/Library/Extensions

I downloaded and installed NVinstall, and picked nvidia 8400gs 256M and rebooted.. I got stuck with a black screen.
So I rebooted to safe mode, and editted /Library/Preferences/SystemConfiguration/com.apple.Boot.plist and removed the device string.
Then I copied all the kexts from my backup directory back to /System/Library/Extensions and rebooted.

Suddenly I have HW accelerated Core Image and Quart Extreme. Can't explain it, but I'll take it.

For monitoring CPU temp, Hardware Monitor (http://www.bresink.de/osx/HardwareMonitor.html) is the only one I've found that works so far (iStat does not )

Also About this Mac does not report any PCI cards.

There guides for this mobo, google a bit

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HP Pavilion Elite m9250f
iAtkos v5i (10.5.8), Asus IPIBL-LB MOD BIOS, Intel Quad Core Q6600, 4GB RAM (800mhz), 2x500GB, nVidia 8600GT (Works), ALC888S (Works), Wireless RT73 (Works), LAN (Works) - How to Install - Blog - Hardware Combos - FAQ by TJ2K7
Macbook Pro 13"
Follow meh: @icchansan

If you just want to support hackint0sh.org with a donation click here

thanks, yes. There is a thread on insanelymac where 3 of us have all used different methods for the install. I tried boot132 for a full retail install, but it didn't work for me (retail install DVD did not boot), so I dropped back to iPC as my method.

all was straight-forward except the video card.

I figure I'll wait for the next chameleon which looks to make the EFI partition method easier, and also make dual-boot so much easier (will d-b with ubuntu).

For now I am up and running with what seems like a reasonably easy install (in retrospect)

Did work for you? maybe your doing something wrong, this mobo is compatible, anyway... here for video, about the chameleon, wait and wait ;P

__________________
HP Pavilion Elite m9250f
iAtkos v5i (10.5.8), Asus IPIBL-LB MOD BIOS, Intel Quad Core Q6600, 4GB RAM (800mhz), 2x500GB, nVidia 8600GT (Works), ALC888S (Works), Wireless RT73 (Works), LAN (Works) - How to Install - Blog - Hardware Combos - FAQ by TJ2K7
Macbook Pro 13"
Follow meh: @icchansan

If you just want to support hackint0sh.org with a donation click here

The mobo was a straightforward install with iPC 10.5.6.

I *thought* I had the 8400gs working. Originally I used nvinject256 (during iPC 10.5.6 install), and when I booted I had a grey background (no fancy OSX Welcome), but the dialog boxes where there, I registered, and when I got to the Desktop, it was 1920x1080 with the background pic, but CI/QE were not enabled.

so I tried setting EFI string with OSX86 tools (I think.. might have been EFI studio), and saving to plist. I also copied all the NV* and Ge* kexts to a backup and removed them from the Extensions dir.

When I rebooted, I got a black screen.. so I rebooted again with single user mode and removed the long device string from boot.plist and copied my kexts back, figuring I'd be back where I started.

Lo and behold I had accelerated QE/CI. I didn't know how, but I didn't care

So I shut down for the night happy.

When I rebooted, it went to a black screen.

Argh.

so I decided to start over. iPC install DVD.. Disk Utility, erase the partition, and re-install with nvinject256. Now that fails for me too.

so I'm trying to read what I can about nvcap and device IDs, etc, and gather as much info as I can and give it another shot.

EDIT: I have PNY GeForce 8400 GS VCG8400SXEB 256MB PCIe , I've seen some suggestions that its ports are not in the same order as most 8400s.. also its PCIe x1 not x16, so I think that changes a 7 to a 0 from most nvcap strings I see (not that I know how to use an NVCAP string yet )

EDIT2: I'll look at the ideas in that thread.. only concern is that the thread is quite old, and not sure if they still apply to 10.5.6? I've seen several mentions of methods that broke around 10.5.3.