Mac OS 9 Discussion > Video Cards, Monitors & Displays
Issues with GeForce 4MX - iMac G4 - M6498 (EMC 1956)
Genie52:
thank you for links aBc! I have https://everymac.com/systems/apple/imac/specs/imac_1.0_17_fp.html . Will try with the version you have linked. I did download 9.2.2. Uni from webarchive but it seems its a different version (I can see difference in sizes). I will try with the version you have posted. Thank you!
edit:
I had to use the one I did before (https://macos9lives.com/smforum/index.php?topic=2143.0) because my iMac does not support OS 9.2.2.
Greystash:
I've been trying to get this working for a while but haven't had much luck. This model will display all color sets and resolutions under OS9, but it needs either video support with drivers or Mac OS ROM modifications to allow this. I'm not sure where to do this within the ROM file but I have seen it done for other models. If you have two partitions (OSX and OS9), the color depth and resolution set in OSX will carry through to OS9 when you restart, but you won't be able to switch after booting into OS9.
I have the 1.0Ghz 15" model (Unsupported OS9) and a 700Mhz (full OS9 support). As darthnVader states here (https://macos9lives.com/smforum/index.php?topic=1173.msg46900#msg46900) the 1.0Ghz model uses a slightly newer graphics chipset which doesn't have OS9 support. I've been trying to override the graphics properties in Open Firmware to be recognised as the older model, to see if that will make any difference. This might be a silly approach but I thought it would be worth a try.
I haven't been able to get far or test this because when the boot process starts Open Firmware is unable to find the display device, which is odd because it can be found and modified when you've booted directly into Open Firmware.
I've saved the following to the NVRAM in Open Firmware:
--- Code: ---dev /pci@f0000000/NVDA,Parent@10
00000110 encode-int " device-id" property
000000b2 encode-int " revision-id" property
" GeForce2 MX" encode-string " model" property
" GeForce2 MX" encode-string " compatible" property
" NVDA,GeForce2MX" encode-string " device_type" property
device-end
--- End code ---
With these changes set in the NVRAM, I boot the computer into Open Firmware again and it loads the NVRAM contents before allowing you to do anything.
In the pictures below you can see that after loading the NVRAM the first line complains that it can't find that hardware address during boot. The strange thing is that these addresses do exist and you can access them by manually entering them in Open Firmware. :o
The only hardware address related to display that it will find during the boot process is:
--- Code: ---dev /pci@f0000000
--- End code ---
None of this device's children can be found during the boot process, so all of the following will produce the same error when loading the NVRAM contents:
--- Code: ---dev agp
dev screen
dev /pci@f0000000/[any child nodes]
--- End code ---
Does anyone know why these device addresses can't be found at boot time?
joevt:
--- Quote from: Greystash on April 13, 2024, 08:32:55 PM ---Does anyone know why these device addresses can't be found at boot time?
--- End quote ---
Normal Open Firmware boot-up does the following: nvramrc probe-all install-console banner
The problem is probe-all is responsible for populating the PCI devices so your nvramrc script doesn't see the PCI devices. To get around this, add probe-all to the beginning of your nvramrc script and add banner to the end of the nvramrc script.
https://68kmla.org/bb/index.php?threads/the-great-gazelle-pci-hack-thread-part-2.38360/post-466488
https://forums.macrumors.com/threads/question-how-powerful-of-a-graphics-card-will-work-in-a-beige-power-macintosh-g3.2303689/
Genie52:
thank you all! will try to play with settings you have mentioned in a weeks time after I come back from travels..
Greystash:
Thanks joevt! That's interesting and answers a few questions I've had in the past!
I tried adding `probe-all` to the beginning of my script, and `banner` to the end, which resulted in the errors displayed in the image below. There is a "can't OPEN device" error, and several USB related errors. The Open Firmware console also locked up so a had to reboot holding the power button, wait for programmers tone etc. until OFW loaded.
Instead I substituted `probe-all` with `probe-pci`, and that seemed to work. No errors and it doesn't complain about not finding the GPU device. :D
Unfortunately this didn't change anything regarding GPU support, and I couldn't see any difference within Apple System Profiler. I'm not expecting this to work, its just an experiment but I did expect to see some differences reported in Apple System Profiler.
If you run `probe-all`, or `probe-pci` within the nvramrc, will it run again afterwards as part of the boot process (overwriting changes), or does this hijack the default boot process?
I'll do some more digging later.
Thanks again joevt!
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