cknight@polyslo.CalPoly.EDU (King Claudius) (03/25/89)
What is the speed of the standard 3.5" Amiga drive in bytes per second?
And secondly, if anyone knows, what is the speed of the Atari ST 3.5" drive
in bytes per second (their drives are supposed to be the fastest; God
knows their the noisiest).
Thanks
--
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
cknight ---King Claudius--- cknight@polyslo.calpoly.edu
Die, Hamlet, DIE! There are three types of people,
me, you, and everyone else.w-colinp@microsoft.UUCP (Colin Plumb) (03/26/89)
cknight@polyslo.CalPoly.EDU (King Claudius) wrote: > What is the speed of the standard 3.5" Amiga drive in bytes per second? > > And secondly, if anyone knows, what is the speed of the Atari ST 3.5" drive > in bytes per second (their drives are supposed to be the fastest; God > knows their the noisiest). Assuming both spin at 300 RPM, both take 0.2 seconds to read a track. Because the Atari puts 9x512=4608 bytes on a track, that's 23040 bytes per second. The Amiga puts 11x512=5632 bytes on a track (11x(512+16)=5808 bytes if you cheat a bit), you get 28160 (29040) bytes per second. I am assuming the Arari is smart enough to start reading whole tracks with the first sector it finds, instead of waiting for sector 1. If it isn't, reduce that figure by 1/3 (to 15360 bytes/sec) to allow for the additional 1/2 track (0.1 sec) average latency. The Amiga never waits to start reading. There is the point that the Amiga always reads full tracks (0.2 sec) while to read just one sector, the Atari has an average 1/2 track latency. So for a point read, the Atari is faster. For bulk reads, the Amiga wins. -- -Colin (uunet!microsoft!w-colinp) "Don't listen to me. I never do." - The Doctor
jesup@cbmvax.UUCP (Randell Jesup) (03/29/89)
In article <67@microsoft.UUCP> w-colinp@microsoft.uucp (Colin Plumb) writes: >cknight@polyslo.CalPoly.EDU (King Claudius) wrote: >> What is the speed of the standard 3.5" Amiga drive in bytes per second? >> >Assuming both spin at 300 RPM, both take 0.2 seconds to read a track. >Because the Atari puts 9x512=4608 bytes on a track, that's 23040 bytes >per second. The Amiga puts 11x512=5632 bytes on a track (11x(512+16)=5808 >bytes if you cheat a bit), you get 28160 (29040) bytes per second. > >I am assuming the Arari is smart enough to start reading whole tracks >with the first sector it finds, instead of waiting for sector 1. If >it isn't, reduce that figure by 1/3 (to 15360 bytes/sec) to allow for >the additional 1/2 track (0.1 sec) average latency. The Amiga never >waits to start reading. Actually trackdisk overhead comes into play here. Trackdisk throughput is about 21-22K/sec including decode, checksum, and transfer to the users buffer for large reads. Overhead should be cut for 1.4, but don't forget filesystem gets in there too, and there isn't a lot of overhead. Most of the time the disk is actually spinning or moving the heads. Even cutting overhead in half will only add 10% or so to the transfer rate. -- Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup
w-colinp@microsoft.UUCP (Colin Plumb) (03/30/89)
jesup@cbmvax.UUCP (Randell Jesup) wrote: > Actually trackdisk overhead comes into play here. Trackdisk > throughput is about 21-22K/sec including decode, checksum, and transfer to > the users buffer for large reads. H'm... can't the trackdisk.device overlap reading one track and decoding another? Actually, I think you'd need multiple track buffers... maybe you could share them between different floppies? Yeah, that's the ticket! It makes the locking a bit more complex, but not too horrible. (I could envision a scheme where you start decoding a buffer and start a DMA into the same buffer, relying on the blitter being faster than the disk DMA. Now *that's* horrible!) > Overhead should be cut for 1.4, but don't forget filesystem gets > in there too, and there isn't a lot of overhead. Most of the time the disk > is actually spinning or moving the heads. Even cutting overhead in half > will only add 10% or so to the transfer rate. Well, thanks for the info. Now I know not to wonder so much when my filesystem fails to do 25K/sec. -- -Colin (uunet!microsoft!w-colinp) "Don't listen to me. I never do." - The Doctor