On 10/1/24 18:29, Tom Gardner via cctalk wrote:
I wouldn't call the 2314 low tech - it was the highest areal density at the time, a breakthru with ferrite heads and very low cost to manufacture. Note I said cost, its profit margin was enormous, in part by putting as much expensive electronics as possible in the control unit. 😊 Actually the 2314 did not ship with the first 360's in 1965; it was announced in April 1965 about 1 year after the 360 announcement and AFAICT from Bitsavers document dates it didn't ship until late 1966, which FWIW, at the Computer History Museum, 1966 is also the date for first shipment of the 2414 and its ferrite heads. BTW the hydraulic actuator design goes back to the 1311 - more or less the same actuator in the 1311, 2311 and 2314.
Well, yes, and in the days of SLT logic, everything was expensive. So, putting as much of the functions in the control unit rather than the drive was good. But, one thing that this mindset caused was that they could not have one drive seeking while another drive was transferring. The entire operation, cylinder seek, rotational seek and data transfer was all one atomic operation. That really killed the throughput of the whole disk system. The reason was that the IBM developers came from systems like 7070 and 7090 where all permanent storage was on tape, and they didn't quite "get" how central disks were going to be to the 360 systems. They had the CKD scheme, where you could search several cylinders for a match of some arbitrary field in the DATA portion of a sector, but this resulted in massive slowdown of the system, as it tied up not only the drive, but the controller and the channel as well! Thus the need for the database system, which would make selecting the desired record much faster.
I didn't mean that the 2314 DISK was low tech, just that the drive, itself, was quite spartan.
Jon
