Re: Fast GCR decoding?

From: Julian Perry <>
Date: Sun, 13 Jan 2013 11:36:01 +1100
Message-ID: <>
Hello Silverdr,

Sunday, January 13, 2013, 11:19:51 AM, you wrote:

> On 2005-11-07, at 20:10, Spiro Trikaliotis wrote:

>> Hello,
>> * On Mon, Nov 07, 2005 at 07:23:09PM +0100 wrote:
>>> Does anyone know if there is a known, substantially faster GCR
>>> decoding algorithm than the one in the drive's ROM?
>> in the 157x, there are other functions than in the 154x which are table
>> driven. These are much faster.

> Is there anything known that would be still faster? AFAIU
> ProfessionalDOS does it faster but with help from its hardware.
> Anyone heard of faster than 1571 but pure software based decoding?

I BELIEVE (but I don't have any direct evidence) that the DolphinDOS
modification used part of the additional RAM, and the larger ROM
routine to employ a less efficient, but faster GCR decode routine.

I have a drive with DolphinDOS -  if time permits later, I'll paw
through the ROMs and see what I find.


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Received on 2013-01-13 01:00:29

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