AST Research proprietary 1 Megabyte RAM module for AST Premium 386 PCs
What Is This Oddball?

• Brand: AST Research (clearly stamped AST on the PCB, part number 202396-001 A).

• Pin Count: 64 pins (a short-lived proprietary edge-connector format used in the late 1980s and early 1990s).

• Capacity: 1MB Parity SIMM (1MBx9-bit equivalent).

• DRAM Specs:8xToshiba TC51C4256-80L (256Kx4-bit, 80ns Fast Page Mode DRAMs).

Why Does It Have Different Chip Counts Front vs. Back?

Take a close look at how the DRAM chips are mapped:

• Front: 5 chips total

• Back: 3 chips total

• Total: 8 chips x4-bit wide dies = 32-bit data bus}

AST used this weird asymmetric 64-pin layout to route a full 32-bit (plus parity/control) memory bank directly onto a single stick for their early 386 computers—specifically systems like the AST Premium 386/16, 386/20, and 386/25.

Back in the late 80s, standard 30-pin SIMMs were only 8-bit wide, meaning a 386DX required four 30-pin SIMMs per bank. Standard 72-pin SIMMs hadn't been widely adopted yet, so AST engineered their own 64-pin, 32-bit wide modules so users could upgrade memory one stick (or two) at a time instead of burning four slots per bank.

Sadly, I lack a system to test this with, so I am forced to sell it as-is, untested, and without warranty.