zz1he@sdcc3.ucsd.EDU (Heather Ebey) (02/18/89)
Does 28ms or 38ms vs 65ms make any difference on a hard disk connected to a MacPlus? Is the MacPlus too slow to take advantage of the faster access?
ech@pegasus.ATT.COM (Edward C Horvath) (02/20/89)
From article <4313@sdcc3.ucsd.EDU>, by zz1he@sdcc3.ucsd.EDU (Heather Ebey): > Does 28ms or 38ms vs 65ms make any difference on a hard disk > connected to a MacPlus? Is the MacPlus too slow to take > advantage of the faster access? Urk! Yes! The SCSI port is *POLLED* on all Macs, not just the Plus: that 28/38/65ms delay is "dead time" -- interrupts can happen, but the program that made the disk request is waiting for completion (even if the PBRead/Write was "asynch". Someday Apple may discover that wonder of 1961 technology, "Direct Memory Access (DMA)". You'll STILL want a fast disk... =Ned Horvath=
steveg@tove.umd.edu (Steve Green) (02/20/89)
....yes, 27ms...... :-)
jwhitnell@cup.portal.com (Jerry D Whitnell) (02/21/89)
From article <4313@sdcc3.ucsd.EDU>, by zz1he@sdcc3.ucsd.EDU (Heather Ebey): > Does 28ms or 38ms vs 65ms make any difference on a hard disk > connected to a MacPlus? Is the MacPlus too slow to take > advantage of the faster access? It depends on the drive (and the software). It can make a difference, but there are a lot of other factors that can affect performance as well. For example, the DataFrame XP40 (the model replaced by the XP 60), used a 65 ms drive (according to the spec sheet). However it was one of the fastest drives available at the time of its release. This is becuase of other software/hardware tricks that SuperMac played to make it faster. The best place to measure a drives performance is at the user's level, not a the drive level. To see if a drive one drive is faster then another, set up your normal configuration and try the things you normally do. Copy some files, launch the applications etc. Playying with the size of the cache can help, if you have memory to spare. -- Jerry Whitnell Several Species of Small Furry jwhitnell@cup.portal.com Animals Gathered Together in a ..!sun!cup.portal.com!jwhitnell Cave and Grooving with a PICT. -- Pink Floyd
wert@cup.portal.com (robert scott comer) (02/21/89)
Yea, so what about dead time? What are you going to do with that time anyway? No matter what system you are using, multiuser or not, that time is dead time FOR YOU. DMA will only help with the overhead of transferring the data from the disk to the memory, a small percentage of the time involved in the transaction. Get the fast disk, if you can afford it , because that is the one thing that will help i/o performance, no matter whether you are connected to a plus, an SE, a II, or a sun. scott out