GW4405A is a 68-pin VRAM SIMM which provides Apple Macintosh computers with 512 kB of VRAM.

High-Quality PCB

GW4405A is built with an ENIG gold-plated, 4-layer PCB, and only new parts are used to build the VRAM SIMMs. All units are tested extensively before shipment, and all SIMMs conform to 80 ns timing or better, ensuring compatibility with all Macintosh models which support 68-pin VRAM SIMMs.

Excellent Signal Integrity

GW4405A features solid power and ground planes. Particular attention was paid to signal integrity, ensuring reliable performance on the fastest machines. The address bus traces are run as asymmetric striplines shielded inside the SIMM PCB, reducing interference generated by large VRAM SIMM arrays such as on the Quadra 700. Ample separation is provided between the DQ and SDQ buses routed on the front-side of the board. Particular attention was paid to the edge-sensitive RAS, CAS, and SCLK signals. These are optimized for minimum length, with large spacing between these edge-sensitive signals and all other signals and buses.

Open-Source Design

GW4405A's design is 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

VRAM Speed

GW4405A is built with 70ns or faster VRAM chips, ensuring compatibility with all Macintosh models.

512 kB / 256 kB SIMM Substitution

On machines which only call for 256 kB VRAM SIMMs, 512 kB SIMMs are supported, but only 256 kB of the total 512 kB capacity can be used. However, do not mix VRAM SIMM sizes on machines which call for either 256 kB or 512 kB VRAM SIMMs. For example, the LC 575 requires either two 256 kB SIMMs or two 512 kB SIMMs. Do not mix sizes in this machine.