GW4402B is a 64-pin ROM SIMM which replaces the original ROM SIMM of a Macintosh II-series or Macintosh SE/30 computer. GW4402B 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

GW4402B and its ROM disk are compatible with the following Macintosh computers:

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

Except for accelerators, all hardware and software we have tested is compatible with the SIMM’s custom ROM. Generally, accelerators with MC68030 processors are fully working, but some accelerators with MC68040 processors are incompatible. In case of incompatibility with the custom ROM, the Mac IIsi and Mac IIx ROMs can be selected using a switch on the SIMM.

Multiple ROM and Disk Images

The GW4402B ROM SIMM has four preprogrammed 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)

ROM images can be rewritten using any 64-pin ROM SIMM programmer such as the CayMac ROMmate. 16 MB of total capacity is available on the SIMM for storing multiple ROM images, but only 8 MB can be accessed at once without powering off the machine and changing the ROM Select switch.

Fast Startup

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

ROM Disk Settings Control Panel

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 and fitment stickers are included with the ROM SIMM. The reinforcing clips fit over the sides of the ROM SIMM socket and brace the SIMM, promoting good electrical contact between the ROM SIMM and the pins on the motherboard connector. Similar in function, the fitment stickers are applied on the back of the ROM SIMM board and thicken it slightly so that the socket pins make better electrical contact with the connector on the motherboard.

Ecologically Friendly, Gold-Plated PCB

GW4402B features a lead-free, ENIG gold-plated, 4-layer PCB and is fully EU RoHS-compliant. All units are tested extensively before shipment. Only new parts are used to build GW4402B, and all GW4402B ROM SIMM modules are manufactured in our semi-automated facility in Columbus, Ohio, in the United States.

Open-Source Design

GW4402B's design is fully open-source. The schematics, board layouts, and driver software are all freely available for commercial and noncommercial use. To download the design files, visit the Garrett's Workshop GitHub page: https://github.com/garrettsworkshop