"Gerhard Postpischil" <[email protected]> wrote in message news:<[email protected]>... > Ron Hawkins wrote: > > Being 1988 the DASD would have been 3380 which spun at 3600 RPM, which is an > > average latency of 8 1/3 msec. 3390s spun at 4200 RPM. 8.32 msec does divide > > evenly by 128 microseconds (128 * 6500 = 832000). I would be surprised if > > the proximity to average latency is anything more than a coincidence though. > > I would be surprised if it isn't, although I'd use a value a > little smidgen higher. The typical I/O requires some setup to > get IOs to handle the request, it needs to be queued, wait until > the device is available, position the heads, search or seek the > record, transfer the data, and clean up. Processors in the late > eighties were fast enough so that only the search or seek > processing took any significant time compared to processing > time. If the disks were favorably positioned at the time of > request, there would be no overhead, vs. maximum overhead if it > just passed the requested record. So half the latency represents > an average; I'd also add a correction factor for arm > positioning, but if you're the only one running, after the first > I/O that also becomes negligible. > > > Gerhard Postpischil > Bradford, VT >
Please, this is, as often in this group, far Off-Topic. Is there anybody who can say something On-Topic, meaning answer Davids question? We are going to 1.10 soon and are very interested in this threads Topic. Kees. ********************************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ********************************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
