Bsrgvty

I recently discovered that the SCSI protocol was, in fact, an improvement on the SASI protocol, which apparently predates SCSI by only a couple of years, appearing in 1978 (but only publicly in 1981). It was only shortly after, in 1982, that the SCSI protocol appeared.

That makes me wonder whether SASI was commercially successful.

What was the popularity, if any, of the SASI protocol?

Some parts of SASI were used in the Atari ST family’s ACSI system, in particular for hard drives connected to that interface — see Application Notes on the Atari Computer System Interface for details. Whether that counts as “popular” depends on your interpretation and the markets you’re interested in.

SASI controllers and hard drives were used in minis too, and at least available for many early micros, and SCSI-1 was designed to be backwards-compatible with it and many SASI controllers were compatible with SCSI-1.

The SASI protocol, if anything, was used by "The Sider" hard drive for the Apple II series of computers. Though hard drives on the Apple II weren't very common, it wasn't until 1985 that "The Sider" appeared and was considerably less expensive than its predecessors and as a result became rather popular in the Apple II community.

That being said, The Sider was based on the Xebec controller which was SASI before the Sider appeared, so production numbers would certainly exceed the Apple numbers.

I'm not aware of other commercial implementations of SASI, but from the Xebec sales alone it would qualify as somewhat successful if anything.

The point is: When SASI was en vogue (and that was only a very short timeframe, because technology was soon superseded with SCSI and the simpler ST506 and later ATA standards), hard disks weren't very popular for low and mid-range computers.

If you look at early hard disks, for a short time (a time frame of maybe 2-3 years in the early 1980s) SASI was the only relevant standard, so market share must have been close to 100%.

Development of early hard disk interfaces for small computers was simply so short that technology developed much faster than standards could really establish themselves in the market.

Some relatively popular computers like the Sharp XC60000 and the Commodore early hard drives for the PET (D9090 and similar) used SASI hard disks.

Note that the change from SASI to SCSI was only a name change, there were no technical changes applied to the interface - So starting in 1981, SCSI and SASI were effectively the same thing, just with a standardized name. Seen from this end, SASI was actually very popular, just under a standardized name that removed "Shugart Associates" from the abbreviation.

Wikipedia knows the following:

Until at least February 1982, ANSI developed the specification as "SASI" and "Shugart Associates System Interface"

However, the committee documenting the standard would not allow it to be named after a company. Almost a full day was devoted to agreeing to name the standard "Small Computer System Interface", which Boucher intended to be pronounced "sexy", but ENDL's Dal Allan pronounced the new acronym as "scuzzy" and that stuck.

Japan.
In Japan, the SASI interface is relatively widely used. We can recall the NEC PC-98 and Sharp X68000 families, as well as less common systems.