. USB keys for disk storage using software striping
get 80 MB/second, 1 millisecond access over USB 2
Someone has already done it and the results weren't all that impressive, quite far from 80MB/sec, which I see as an impossible number to reach unless you've got multiple USB2 Root Hubs (which would eat up valuable PCI slots), along with high speed flash memory.
Probably 4x cheaper just doing it with 2 external 7,200RPM notebook drives.
. USB keys for disk storage using hardware striping in SCSI
get 640 MB/second, 2 millisecond access over SCSI adaptor
(the above 2 should throttle back so as to not cause
interference with other main memory access)
Building an Ultra640 to USB2 interface is impossible due to the signaling and electrical limitations of both devices, and because of the internal speed of the flash memory, you'd never come close to 640MB/s
. cache memory using 64 MB or more of 10 ns memory
SRAM would be faster and the choice I would use but obscenely expensive. If you really want one, Cenatek will sell you one with between 256MB and 4GB of 7.5ns memory (ie, it's been done already)