USR quad modems... (ontopic - really!)

[Don]

Tony Duell wrote:
>>> It's probably possible to add external circuitry to turn that back into a 
>>> normal 18 bit address and hang SRAM off it, but I think it's more work 
>>> than finding some 41256s...
>> I would assume the controller would exploit page mode references
>> (especially when dealing with sequential accesses like video).
> 
> I am not sure, and the service manual (which I have) doesn't make any 
> obvious reference to this.

Any timing diagrams for DRAM access?  You'd recognize the page mode
cycles by the lack of a 1:1 pairing of RAS with CAS.