>         Is the 4 Megabit (various cfg's 512KX8, 1MX32) the largest
> available SRAM?
>

White Microelectronics have a 512Kx32 SRAM module that is
configuration to 1024Kx16 and 2Mx8.  But its packages are a
66-pin HIP (?), or a 68-lead CQFP.

-tim