Depends on the box, but some years ago, I picked up an old slotted-Xeon server at a swap for a few bucks, and it had 32 DIMM slots on an enormous memory sub-board. Took registered or buffered ECC, as I recall. I scored a few modules on eBay and put 256MB into it, I think it would've gone to 4GB if I filled all the slots.

But the hard drives were SCSI SCA-2, which I believe maxed out at 40MB/s but in practice the drives were much slower. So yes, there was probably a point in time where a reasonably-beefy box would have had the specs you describe.

20 MHz --> 40M samples per second (Nyquist). 16 bits per channel, and two channels (I, Q).

40000000 x 2 x 2, so... about 160 MB/sec?

It's a lot of data. It wasn't happening with the disk I had on hand, so I went for the ramdisk thing. 1.6 GB of memory? That I did have.

I had a P3 desktop with a UDMA hard drive (33MB/s theoretical peak) and 128MB of RAM. A workstation of the time would have over 512MB of RAM and a SCSI drive that might not sustain 40MB/s.

Going back further, in 1995, a SPARCstation 20 had a SCSI-2 controller (10MB/s maximum transfer rate) and could be fitted with 512MB of RAM.

I mean SATA 3 has a bit more than 500MB/s right, and PCIe SSDs run at between 1-4 GB/s? so a machine today (at least 8GB of RAM maybe in the hundreds) would have an even bigger ratio between memory size and disk transfer speed.