SIMM which replaces the original ROM SIMM of a Macintosh II-series or Macintosh SE/30 computer. The ROM comes preprogrammed with several ROM images including a customized, 32-bit clean Macintosh ROM. The customized ROM allows your Macintosh to use more than 8 MB of RAM, disables RAM test for faster booting, and has a bootable ROM disk. Using a switch on the ROM SIMM, either a System 7.1 or a System 6 ROM disk image can be chosen. Both disk images are loaded with various utilities. The ROM disk can also be mounted when booting from another disk. Along with the customized ROM, unmodified Mac IIx and IIsi ROMs are preprogrammed on the SIMM and can be selected using the ROM Select switch on the SIMM board.

Compatibility

The ROM is compatible with the following Macintosh computers:

• • Macintosh SE/30
  • Macintosh IIx
  • Macintosh IIcx
  • Macintosh IIci
  • Macintosh IIsi
  • Macintosh IIfx

Multiple ROM and Disk Images

The ROM SIMM has four ROM images selectable via the ROM Select switch:

• Customized ROM with System 7.1 Update 3 ROM disk and RAM test disabled (compatible with all supported Macintosh computers and based on Mac IIsi ROM)
• Customized ROM with System 6.0.8 ROM disk and RAM test disabled  (compatible with all supported Macintosh computers and based on Mac IIsi ROM)
• Unmodified Macintosh IIsi ROM (compatible with all supported Macintosh computers)
• Unmodified Macintosh IIx ROM (only compatible with Macintosh IIx, IIcx, and SE/30)

Fast Startup

It takes about 10 seconds to boot from the included ROM-based System 7.1, so you can begin working with programs or playing games almost instantly. The System 6 ROM disk image boots even faster.

ROM Disk Settings

A control panel allows your preferences for the built-in ROM disk to be changed. You can boot from the ROM disk, mount it under another boot disk, or hide it from the desktop completely. Of course, you can always press “R” during startup to boot from ROM independent of your saved preferences. It’s also possible to enable RAM disk mode, which allows writing data to the ROM disk, although data stored is not retained between restarts. The RAM disk is enabled by pressing “A” during startup, or by enabling the corresponding setting in the control panel.

ROM Reinforcing Clips and Fitment Stickers Included

Many Macintosh models made before 1991 use a ROM SIMM socket with plastic retaining clips. Over time, these clips tend to weaken and may no longer hold a ROM SIMM in proper contact with the contact pins in the socket. To address this problem, plastic reinforcing clips are available on websites like Thingiverse.

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