When I read it years ago the most surprising to me was density of 40MB IDE drive. ST-157A sold all the way to 1992 was barely more sophisticated than a DD flopp

When I read it years ago the most surprising to me was density of 40MB IDE drive. ST-157A sold all the way to 1992 was barely more sophisticated than a DD floppy disk. ~10000 bpi while DD floppy is ~9000. Heads are narrower and there is more tracks per surface, 650 vs 135 TPI, and rigid magnetic surface lets it spin faster, thats it.