Archived posting to the Leica Users Group, 2001/04/03
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Pascal wrote: > On 02-04-2001 18:26, Henning Wulff wrote: > > >They are SCSI II. > > I stand corrected :-) > > Must have been misled by the fact that the scanner works much faster now > that I use it via a SCSI Ultra PC Card, instead of the built-in SCSI port > on my previous Mac. > Those built-in ports had a max throughput of 5 MB/sec (standard SCSI) > while SCSI II has a max of 10 MB/sec and Ultra 20 MB/sec. > Just by using a SCSI PC Card I could significantly increase the > performance of the Nikon LS-2000 (but it's SCSI II and not Ultra). > > It also means that my Iomega Jaz 2 GB is slowed down since it is on the > same SCSI chain and the Iomega does use Ultra SCSI :-( <snip> Only if you are scanning and accessing the Iomega at the same time. Each peripheral on the SCSI II (or SCSI-3) bus negotiates a transfer rate with the host. Fast and slow devices run at their negotiated speeds. The whole bus does not slow down to the speed of the lowest peripheral. Things get different on a LVD (low voltage differential) bus when attaching SE (single ended) peripherals. If memory serves the maximum transfer on a SE bus is 20 megatransfers a second (20 MB if it's 8 bits wide, 40 MB if its 16 bits wide) One question would be just how fast can a scanner generate data? Certainly parallel SCSI keeps moving up in speed. Ultra-160 is out (160 MB/sec) the Ultra-320 spec is now firm and those devices are starting to show up. The standards committe is working on Ultra-640 (640 megabytes/secons) Dennis