> How fast does the data need to be written and read?  Is it ever read?
> (If not, there's no need to store it...).  How often is the data
> re-written?  Is the use mostly to write once then read very rapidly, or
> is it read and written rapidly?
>
Ok, here it is:

It's a PIC1674 with an AD676 parrallel, 16-bit A/D attached.  It will
need to read about 60,000 samples from the A/D at 100 Hz.  I'd like
to be able to throw the samples into the RAM buffer in at most 1 ms.
Right now I'm running low on I/O lines, so I'd like the RAM to be
serial.  I'm also going to add another A/D to the system, meaning not
only will my timing requirements get tighter, but I'll need twice as
much RAM to store the data.  Anyway, the data will sit in the ram
until the host PC decides to get it by RS232 from the same PIC.

Given these problems, I think it is safe to say the following:

I don't need or want non-volitile storage because of
speed/complexity/endurance problems.

I need serial interfaceing becuase of the lack of I/O lines.

I need at LEAST 256 KB of RAM to store a potential 64,000 samples of
two 16-bit A/D's.

Any more questions, please ask...  I'd like to make a decision pretty
soon...

Thanks for the help!