List of Seagate model number codes (pre-2011)

This is a list of Seagate model number codes used on Seagate hard drive models prior to 2011, when a new format was introduced.

Prefix: ST or STM

All pre-2009 Seagate model numbers begin with ST. In addition, an "M" is added to the prefix (to become STM) if the drive is branded as a Maxtor.

First digit: Form factor

The first digit after the prefix (so the third digit in Seagate drives, or the fourth digit in Maxtor drives) denotes the form factor of the drive in question.

Code	Form factor	Notes
3	3.5"
9	2.5" 9.5 mm or 7 mm	Used by 7 mm Momentus Thin drives despite the 9 denoting a 9.5 mm z-height, due to a prospective 7 code conflicting with 1.8" drives.
7	1.8"

Capacity number

The next up to two, three or four digits indicate the drive's capacity, in gigabytes. For example, the ST380817AS has an 80 GB capacity, the ST3500312CS has a 500 GB capacity, and the ST31000528AS has a 1,000 GB (1 TB) capacity.

Second digit: Cache

Ignoring the capacity digits, the second digit refers to the drive's amount of cache RAM. The scheme was changed starting with the ST3250310AS, moving from the last digit of the actual cache to a sequential amount that doubles the amount of the previous, starting with 3 equalling 8 MB.

Code	Cache	Scheme
2	2 MB	Old
3	8 MB	New
4	16 MB	New
5	32 MB	New
6	16 MB	Old
	64 MB	New
8	8 MB	Old

Third digit: Platter count

The third digit indicates the number of platters. For example, the ST380817AS has one platter, but the ST9320320AS has two.

Fourth digit: Revision

The fourth digit indicates the revision of the drive, and is used to disambiguate models with the same specifications but different generations, families or platforms. For example, the ST9120310AS and ST9120315AS are different generation models.

Suffix: Business unit and interface

The letter suffix indicates the business unit as well as interface of the drive.

Suffix	Business unit	Interface
A	PC	PATA
AS	PC	SATA
ACE	Pipeline	PATA
SCE	Pipeline (pre-F3)	SATA
CS	Pipeline (F3)	SATA
NS	Enterprise	SATA
SS	Enterprise	SAS
AV	Surveillance	PATA
SV	Surveillance	SATA
AM	Automotive	PATA