Path: utzoo!attcan!utgpu!watmath!iuvax!purdue!haven!grebyn!ckp
From: ckp@grebyn.com (Checkpoint Technologies)
Newsgroups: comp.sys.amiga
Subject: Re: Are there any programs that allow reading Apple ][ disks?
Summary: GCR table already in the Amiga? Where?
Keywords: disk encoding, MFM, GCR, 13-sector, 16-sector, ProDOS, 5.25, 3.5
Message-ID: <12938@grebyn.com>
Date: 16 Aug 89 14:57:07 GMT
References: <495@tardis.Tymnet.COM> <15704@pollux.UUCP>
Reply-To: ckp@grebyn.UUCP (Checkpoint Technologies)
Organization: Grebyn Timesharing, Vienna, VA, USA
Lines: 18

In article <15704@pollux.UUCP> bjc@pollux.UUCP () writes:
>
>The Amiga has a GCR lookup table built in.  In fact, you can use GCR if
>you prefer, but it only works half as fast as the MFM encoding.  
>The RKM states that the GCR capability in the Amiga is the Apple version.
>
As far as I know, the Amiga does not have a GCR translation table built
in. It does have the ability to read CGR disks (witness: Disk-2-Disk and
Mac-2-Dos and AMAX), but this is because the Amiga's disk controller
gives the CPU data below the formatter level, so the CPU can perform
whatever encoding it desired. GCR is generally slower than the Amiga's
MFM scheme, because the blitter can be used to encode MFM, while the CPU
must do the GCR encoding/decoding.
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