Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!apple!oliveb!amiga!cbmvax!jesup
From: jesup@cbmvax.UUCP (Randell Jesup)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Questions on the floppy drive hardware
Message-ID: <7762@cbmvax.UUCP>
Date: 28 Aug 89 17:33:36 GMT
References: <2117.AA2117@geo-works> <7697@cbmvax.UUCP> <8908281131.AA15119@jade.berkeley.edu>
Reply-To: jesup@cbmvax.UUCP (Randell Jesup)
Organization: Commodore Technology, West Chester, PA
Lines: 26

In article <8908281131.AA15119@jade.berkeley.edu> U211344@HNYKUN11.BITNET (Olaf 'Rhialto' Seibert) writes:
>In article <7697@cbmvax.UUCP> jesup@cbmvax.UUCP (Randell Jesup) writes:
>>       The WORDSYNC compares at each bit.  If it sees a match, it will

>Does this mean that WORDSYNC has effect during the complete DMA
>transfer, i.e., that it re-syncs when it encounters the sync word in
>the middle of the track? Or is it (as I originally thought) that
>WORDSYNC only determines when the DMA starts and has no effect
>thereafter?

	It continues to sync as long as the transfer continues.

>>       PRECOMP 0&1 determine the amount of precomp when writing, from 0ns
>>for 00 to 560ns for 11.  For floppies, you need 00 for tracks 0-79 (0-39
>>for 5.25" drives), 01 for the inner tracks (140ns).
>
>I know just enough about hardware to be dangerous, so I must ask:
>What exactly *is* precompensation, and what is its use?

	When the bits are closer together on the inner tracks, you have to
tweak the timing of bits going out.

-- 
Randell Jesup, Keeper of AmigaDos, Commodore Engineering.
{uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.cbm.commodore.com  BIX: rjesup  
Common phrase heard at Amiga Devcon '89: "It's in there!"