Seagate ST-251
The ST-255/ST-251 is a family of MFM harddisks, manufactured by Seagate Technology. It has a ST506/ST412 interface.
The ST-238/ST-277 used RLL modulation, increasing the amount of sectors per track, from 17 to 26. Therefore increasing the capacity with the same hardware.[1].
It was possible to use a good ST-225 with an RLL interface board, and increase the capacity without the higher cost of the company certified RLL models [2]
It was a very popular harddisk model, mostly used in the era of the IBM XT clones.
Variants
- ST-225 MFM 20MB capacity.
- ST-251 MFM 42MB capacity.
- ST-251R RLL 43MB capacity.
- ST-238R RLL 33MB capacity.
- ST-277R RLL 66MB capacity.
The similarity in storage between ST-251 and ST-251R, while expecting it to increase because of RLL use, is caused by the reduction in the number of head from 6 to 4.
Notes
Seagate at a later date published one datasheet for ST251, ST251R and ST277R, demonstrating the family lineage.
References
- ↑ "ST251_ST251R_ST277R_Product_Manual" (PDF). bitsavers.org.
- ↑ "Seagate_ST-251, Notes". Lo-tech Wiki.
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