Article View: comp.sys.amiga.tech
Article #12263Re: Ohhh, just another hack idea.
From: Randell Jesup
Date: Thu, 20 Apr 1989 22:47
Date: Thu, 20 Apr 1989 22:47
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1535 bytes
In article <89Apr19.165456edt.9318@ois.db.toronto.edu> fche@db.toronto.edu (Frank Eigler) writes:
>Another question, something in the same area. Is it possible/has anyone
>ever written a trackdisk.device replacement that uses RLL format instead
>of MFM on a floppy?
No.
>Or, is it possible with the hardware at all?
Probably yes, though it may require better than normal media
(just as some ST506 drives can't handle RLL). I suspect the hardware in
paula and the drives could do it, though I'm not certain. The real killer
is encode/decode. MFM decode is trivial (((word[i] & 0x55555555) << 1) |
(word[i+(BUFFSIZE/2)] & 0x55555555)) - I may have which word is shifted
wrong, check the RKM. The blitter can do that in one pass, and store it in
the users buffer. Decode is trickier, takes 4 passes, but the blitter can
still handle it. RLL would be real tough with the blitter.
--
Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!apple!oliveb!amiga!cbmvax!jesup From: jesup@cbmvax.UUCP (Randell Jesup) Newsgroups: comp.sys.amiga.tech Subject: Re: Ohhh, just another hack idea. Keywords: Bigger floppy drive time Message-ID: <6655@cbmvax.UUCP> Date: 20 Apr 89 22:47:07 GMT References: <10751@mcdphx.phx.mcd.mot.com> <89Apr19.165456edt.9318@ois.db.toronto.edu> Reply-To: jesup@cbmvax.UUCP (Randell Jesup) Distribution: na Organization: Commodore Technology, West Chester, PA Lines: 20