Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!zaphod.mps.ohio-state.edu!swrinde!ucsd!ucbvax!van-bc! From: lphillips@lpami.wimsey.bc.ca (Larry Phillips) Newsgroups: comp.sys.amiga.hardware Subject: Re: GVP Trade-in Keywords: SCSI, GVP Message-ID: <1914@lpami.wimsey.bc.ca> Date: 29 Aug 90 01:47:25 GMT Lines: 36 Return-Path: To: van-bc!rnews In <552@DIALix.UUCP>, bernie@DIALix.UUCP (Bernd Felsche) writes: > >Another consideration is the speed of the filesystem. AmigaDOS >isn't exactly renowned for filesystem performance, even with FFS. >It involves significant CPU cycles to convert the raw SCSI data into >something which DOS presents to the user (FFS is a _lot_ better than >the original FS). When you measure the average transfer speed, the >filesystem (and trackdisk.device) get in the way and give you a >distorted view of what the hardware _can_ do under ideal >conditions. Whoops! You were doing just fine right up to this point. Under FFS, there is no need to massage any data. The FS issues the read, and the 'raw SCSI data' is brought in, left as is, and put into the destination memory. With DMA, it gets there without the processor having to do it, and in any case, the data is the same as when it came over the SCSI bus. Under OFS, the data had to be placed in a buffer in order to strip out the Amigados overhead present in every sector, and then sent to its destination, so your statement is true for OFS. If you count relocation and scatter loading to be 'file system overhead' (which I don't, then your statement is also true for any file system capable of storing programs. -larry -- It is not possible to both understand and appreciate Intel CPUs. -D.Wolfskill +-----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca -or- uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 -or- 76703.4322@compuserve.com | +-----------------------------------------------------------------------+