Memory Upgrades: Mac LC II; Performa 400, 405, 410, 430

The Mac LC II (a.k.a. Performa 400, 405, 410, and 430) has 4 MB of RAM soldered to the motherboard and room for two additional SIMMs. (Apple says that some LC IIs have 2 MB of onboard RAM, but I have never run into one.)

Macintosh LCWith the rear of the computer away from you, you will see two SIMM sockets on the right side of the motherboard. These can be filled with 1 MB, 2 MB, or 4 MB SIMMs. SIMMs must be 100ns or faster and of the 30-pin variety.

You can also upgrade video memory (VRAM) from 256 KB to 512 KB.

Mac LC II page from Apple Memory Guide

Mac LC II page from Apple Memory Guide.

  • To add 2 MB, insert 1 MB SIMMs in each socket.
  • To add 4 MB, install 2 MB SIMMs in the SIMM sockets.
  • To add 8 MB, put 4 MB SIMMs in the memory slots. Note that an LC II with 8 MB of additional RAM will only see 10 MB with this upgrade, not the 12 MB you might expect. This is a peculiarity of the computer’s design and not a problem with RAM.

VRAM, Where More Memory Means Less Speed

The LC II ships with 256 KB VRAM, which supports 8-bit/256-color video at 512 x 384 pixels (Apple’s 12″ color display), 4-bit/16-color video at 640 x 480 pixels.

You can upgrade this to 512 KB by replacing the old SIMM with a 512 KB VRAM SIMM, 100ns or faster. This will support 16-bit/65,000 color video at 512 x 384 pixels and 8-bit/256-color video at 640 x 480 pixels.


  • If you have less than 10 MB installed, upgrade to 10 MB.

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