Re: Fast GCR decoding?

From: Groepaz <>
Date: Mon, 14 Jan 2013 11:25:18 +0100
Message-Id: <>
On Sunday 13 January 2013, you wrote:
> On 2013-01-13, at 07:30, Groepaz wrote:
> >> 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?
> > 
> > thats basically just an eprom with an huge lookup table though (the cbm
> > dual drives do it in a similar way)
> Like putting bits on address lines and reading the outcome from data lines?
> It could be an option, depending on how "huge" the table has to be... It
> can't be 40 bits so some bit fiddling has to be done anyway.
> Also I found a post by Jim Drew on Lemon64, where he admitted to have
> decoded GCR in real time thanks to extra RAM on the SC+ card and "creative
> tables". Since he's got "only" 8K of extra RAM, he had a hard limit on the
> size of the table. If I fit into 8K and have GCR decoded in RT I can't
> have any more wishes ;-) How is it done in dual drives?

he didnt do it in "realtime" (as in: decode on the fly in a single revolution) 
- he did pretty much the same as AR did (and everyone else really). you can 
generally assume its like that when jim starts babbling =P


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Received on 2013-01-14 11:00:03

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