The GW4194A RAM SIMM is a 4 MB, 30-pin "PAL SIMM" DRAM SIMM designed for use with the Apple Macintosh II and Macintosh IIx. GW4194A is sold as a 16 MB kit of four 4 MB SIMMs.

High-Quality PCB

GW419X-series RAM SIMMs are built with an ENIG gold-plated, 4-layer PCB, and only new parts are used to build the SIMMs. All units are tested extensively before shipment.

Excellent Signal Integrity

GW419X-series RAM SIMMs feature solid power and ground planes. Particular attention is paid to signal integrity, ensuring reliable performance on the fastest machines. Data and address buses are routed on separate layers as much as possible to minimize crosstalk. All bottom-side traces are run as asymmetric striplines shielded inside the SIMM PCB, reducing interference generated by large SIMM arrays. Particular attention was paid to the edge-sensitive RAS and CAS signals. These were optimized for minimum length, with ample spacing provided between these edge-sensitive signals and all other signals and buses. All GW419X-series SIMMs are non-composite 2- or 3-chip designs, reducing address bus loading compared to 8- and 9-chip SIMMs.

Open-Source Design

The GW419X-series RAM SIMM designs are fully open-source. The schematics and board layouts 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

Compatibility Notes

Utilizing the full 16 MB capacity of the GW4194A "PAL SIMM" kit requires either the MODE32 software extension or a compatible ROM update.