Disk I/O can be done either in PIO (Programmable I/O) or DMA (Direct Memory Access) modes, with the latter being typically much faster. DOS, by default, does not support DMA, while Windows does, and that's probably the cause of the differences you experienced.

There exist DOS DMA drivers which you can use to speed up disk I/O in DOS, however you must not load them in any DOS session that you plan to run Windows from, because they will conflict with the existing Windows disk drivers.

See this thread:
UDMA drivers for DOS (Latest)

Another option is running SMARTDRV, especially handy for speeding up reads from a CD but won't always be the answer. Is supplied with DOS and the defaults aren't bad for a quick test.

BushLin wrote:

Another option is running SMARTDRV, especially handy for speeding up reads from a CD but won't always be the answer. Is supplied with DOS and the defaults aren't bad for a quick test.

Just be careful with enabling write-back caching, as any crash, power loss or hiccup could cause data loss. I've had games get corrupted and require a reinstall when the game decides to freeze in the middle of a cached write.

clueless1 wrote:

Just be careful with enabling write-back caching, as any crash, power loss or hiccup could cause data loss.

That's good advice. I always load SMARTDRV with the /X switch to disable write-behind caching.