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128Mb SDRAM ICs limitation on original "Bronze Keyboard" Powerbook G3

Q: Using 8x256 Mbit devices (ICs) to create 256 Mbyte SO-DIMMs doesn't work properly on the pre-Firewire, "Bronze Keyboard" Powerbook G3.

Why do these ICs not work properly?

A: The "Grackle" memory controller, used in the original (pre-Firewire) "Bronze Keyboard" and the previous Powerbook G3s, does not support 256 Mb devices as it lacks the extra "column" address to go higher than 128 Mb. These limits are implied in the RAM Expansion section, Table 4-6 of the PowerbookG3 developer note.

However, you can get to 1 GB of memory using 128 Mb devices as long as they use 4 K refresh rates.

Powerbooks using the "Uni-N" memory controller, as in the (Firewire) "Bronze Keyboard" Powerbook G3 and the current Titanium Powerbook G4, have no 128 Mb device restriction.

Titanium Powerbook G4 Developer Note

[Jun 22 2001]

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