Path: utzoo!attcan!uunet!lll-winken!ames!think!bloom-beacon!tut.cis.ohio-state.edu!rutgers!att!pegasus!ech
From: ech@pegasus.ATT.COM (Edward C Horvath)
Newsgroups: comp.sys.mac
Subject: Re: Does 38ms vs 65ms make any difference?
Message-ID: <2597@pegasus.ATT.COM>
Date: 20 Feb 89 03:26:43 GMT
References: <4313@sdcc3.ucsd.EDU>
Organization: AT&T ISL Middletown NJ USA
Lines: 14

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=