Kernel uses only half of Mac IIci memory with built-in video
Hello,
When booting modern kernels (4.x or 5.x) on a Mac IIci, the kernel sees
only half of installed memory if the built-in video is used. Using a
Nubus video card, all of the installed memory is seen. This may be a
Penguin issue, though it's not clear why the kernel is ignoring
available memory. I'm documenting it here in case anyone has an idea
how to fix it.
With 128 MiB memory installed and using built-in video:
...
Mar 10 18:22:34 maciici kernel: Detected Macintosh model: 11
Mar 10 18:22:34 maciici kernel: Apple Macintosh IIci
Mar 10 18:22:34 maciici kernel: Ignoring memory chunk at
0x50000:0x3fb0000 before the first chunk
Mar 10 18:22:34 maciici kernel: Fix your bootloader or use a memfile to
make use of this area!
Mar 10 18:22:34 maciici kernel: Built 1 zonelists, mobility grouping on.
Total pages: 16240
Mar 10 18:22:34 maciici kernel: Kernel command line: root=/dev/sda4
Mar 10 18:22:34 maciici kernel: PID hash table entries: 256 (order: -2,
1024 bytes)
Mar 10 18:22:34 maciici kernel: Dentry cache hash table entries: 8192
(order: 3, 32768 bytes)
Mar 10 18:22:34 maciici kernel: Inode-cache hash table entries: 4096
(order: 2, 16384 bytes)
Mar 10 18:22:34 maciici kernel: Sorting __ex_table...
Mar 10 18:22:34 maciici kernel: Memory: 60472K/65536K available (3274K
kernel code, 248K rwdata, 732K rodata, 112K init, 137K bss, 5064K reserve
d, 0K cma-reserved)
...
Using a Nubus video card, the problem goes away:
...
Mar 11 10:57:42 maciici kernel: Detected Macintosh model: 11
Mar 11 10:57:42 maciici kernel: Apple Macintosh IIci
Mar 11 10:57:43 maciici kernel: Built 1 zonelists, mobility grouping on.
Total pages: 32480
Mar 11 10:57:43 maciici kernel: Kernel command line: root=/dev/sda4
Mar 11 10:57:43 maciici kernel: PID hash table entries: 512 (order: -1,
2048 bytes)
Mar 11 10:57:43 maciici kernel: Dentry cache hash table entries: 16384
(order: 4, 65536 bytes)
Mar 11 10:57:43 maciici kernel: Inode-cache hash table entries: 8192
(order: 3, 32768 bytes)
Mar 11 10:57:43 maciici kernel: Sorting __ex_table...
Mar 11 10:57:43 maciici kernel: Memory: 125380K/131072K available (3274K
kernel code, 248K rwdata, 732K rodata, 112K init, 137K bss, 5692K reser
ved, 0K cma-reserved)
...
-Stan Johnson
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