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Fixed Radeon 9250 ROM RAM sizing issue
Posted by: The Finale of Seem on 2026-10-03 11:42:20 I've had an issue with the Radeon 9250 ROM reporting half of the available memory in both 64-bit and 128-bit cards. With some (okay, a lot of) help from Claude, I've got a version of the ROM that tweaks the RAM size tables. It seems that the table topped out at 64MB per channel, so a useless 8MB per channel entry was removed to make way for a new 128MB per channel maximum. It now reports the correct amount on a couple of 64-bit, 128MB cards and a 128-bit, 256MB card. Also fixes the incorrect checksum that the previous ROM had, though I don't think that caused any problems. If anyone finds a 512MB card then another entry could be added that tops out at 256MB per channel, though at that point it feels kinda pointless. I'm not sure if this has been done yet as I've been using the ROMs off of the old Macelite wiki and finding stuff like this outside of that can be like a needle in a haystack, but I've got the modified ROM here if anyone wants it.
Posted by: joevt on 2026-10-03 22:58:47 512 MB BAR requires an Open Firmware nvramrc patch for Power Macs with ROMs older than 5.1.7f1 (August 2004 for 64-bit Power Macs) or older than 4.8.5f0 (April 2004 for 32-bit Power Macs). https://forums.macrumors.com/thread...l-work-in-a-beige-power-macintosh-g3.2303689/ I suppose you can have a BAR that is smaller than the actual VRAM size. Sometimes a BAR is larger than the VRAM size. PCIe cards with REBAR (resizable BAR) will default to something small like 256 MB. An nvramrc patch could change the resizable BAR to 512 MB or 1 GB. You can put PCIe cards in a PCI Mac with an adapter. Every Power Mac requires a nvramrc patch for 1 GB BARs. I haven't tried it. Linux with a modern PCIe card? 2 GB is probably impossible for Power Macs since I/O is limited to < 4 GB and the 2 GB window at 0x00000000 is used for RAM and the window at 0x80000000 is used for other I/O, Memory controller, and ROM.
Posted by: The Finale of Seem on 2026-10-03 23:58:42 I know the OF patch is needed for 512MB of VRAM. I just considered it pointless on a 9250, like putting a nitrous injector on a clown car.
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