History (1991): 400MB Native Per Cartridge on IBM 3490E

To double capacity of its 3480/3490 magnetic cartridges based on longitudinal recording and reach 400MB, IBM is offering a new drive that doubles the number of tracks, from 18 to 36.

First there is a read/write operation on 18 tracks in the first path forward, then on the 18 other ones in the opposite direction.

This system doesn’t improve data transfer rate that still is 4.5MB/s but avoids to rewind the cartridge and can read previous 200MB 18-track cartridges.

The new models also offer data compression with the IDRC system (Improved Data Recording Capability) from IBM that, according to the manufacturer, can triple the capacity of the tape that can therefore store 1.2GB.

This new 3490E (for Enhanced) models are connectable by optical fibers with the ESCON (Enterprise Systems Connection Architecture) concept, this allows the drives to be 5.6 miles away from the host processor and takes advantage of the 9MB/s transfer rate, theoretically as soon as 4Q91.

With this operation, Big Blue is trying to convince its users to switch from 3480 to 3490 that have not been very successful.

IBM has withdrawn several 3480 models, the A11 and B11 in December 1990, the A22 and B22 will be withdrawn in May.

Two series exist for the 3490Es, the first one (A10, A20, B20 and B40) for ES/9000 mainframes and large S/370 ones, the second (D41, D42) for mid-range S/370 systems. With large systems, you can opt for a control unit A 10 ($62,000) or A20 ($117,000) that can pilot 8 and 16 tape drive subsystems respectively.

Two subsystems are offered, the B20 ($72,000) with 2 self-threading tape transports, and the B40 ($113,000) containing 4 transports.

This means that in the maximum configuration, knowing that each transport has a 6-cartridge stacker, you can reach a capacity of 115.2GB on tape (16 stackers, 96 cartridges with 1.2GB each).

These models will be ready beginning on April. As of June, units for mid-range S/370 will be available. The D41 ($71,900 or $4,030 per month for rent) and the D42 ($99,900 or $5,525 per month) are magnetic tape subsystems that have one or two transports respectively.

Just a few weeks after IBM’s 3490E announcement, Hitachi Data Systems was replying with its HDS 7490E series based on the same two-direction 18-track technology but the availability has not been announced yet.

All compatible manufacturers will most probably follow IBM: Cipher, Comparex, Fujitsu and Memorex.

With this 400MB capacity, IBM’s cartridge is coming closer to the capacity of 4 or 8mm helical scan tapes, but, still keeping its unpaired transfer rate performances

This article is an abstract of news published on the former paper version of Computer Data Storage Newsletter on issue 39, published on April 1991.