Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!husc6!think!ames!oliveb!sun!pepper!cmcmanis From: cmcmanis%pepper@Sun.COM (Chuck McManis) Newsgroups: comp.sys.amiga Subject: Re: Fish Disk benchmark result Message-ID: <24006@sun.uucp> Date: Wed, 22-Jul-87 19:00:35 EDT Article-I.D.: sun.24006 Posted: Wed Jul 22 19:00:35 1987 Date-Received: Sat, 25-Jul-87 02:01:05 EDT References: <337@palladium.UUCP> <1638@xanth.UUCP> Sender: news@sun.uucp Reply-To: cmcmanis@sun.UUCP (Chuck McManis) Organization: Sun Microsystems, Mountain View Lines: 35 In article <1638@xanth.UUCP> kent@xanth.UUCP (Kent Paul Dolan) writes: >No complaint against the Pal Jr., but just generically; with the state of the >art in hard disk file transfer in the multiple megabytes per second range, >why are we still down in the 10K's of bytes? Ok, the spec for *any* ST-506 compliant drive is 5 megaBITS per second which is 625K bytes per second. For ESDI drives the data transfer rate is 10 megaBITS per second or 1.25 MegaBYTES per second. Disk to host adapters (like a lot of SCSI thingies are) are usually capable of 1.2 megabyte capable with speeds up to 4 megabytes/second when run 'synchronously'. They basically buffer up the requested data in an on-board buffer and then squirt it out to you when they have it all. Some of the new SCSI chips can go faster than this. The Amiga's fastest transfer rate for bytes is about 600K bytes per second ( mov.b (a0)+,(a1)+, jmp $ ) 1.2 meg if you transfer words. Disks with DMA channels win big in this situation, although only 2X to 3X in raw transfer rate so that is the absolute best you could hope for. Now tack on the over -head of going from a request for a block in the file system and which is translated into a device request which is translated into a physical request which is copies back into the address space of the user and then notified. It can be done faster, but don't ever expect 'multiple megabytes' per second on a stock Amiga. > Speeds this low make disk based >virtual memory a real loser (although at today's prices, extended address >space ramdisk looks like a real possibility for virtual memory on PC's with >limited personal memory, like the Amiga). This doesn't parse for me. If you put RAM on the Amiga you can use it, are you thinking about x86 type machines? --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.