Re: Fast GCR decoding?

From: Nicolas Welte <>
Date: Mon, 14 Jan 2013 12:40:48 +0100
Message-ID: <>
On 14.01.2013 12:23, wrote:
> I found one more claim similar to that, possibly coming from a less "controversial" source:
> "I de-coded a [w]hole block in real-time during reading and writing. Not first read in the buffer and then de-code."
> It comes from a guy who is the author of (faster than Dolphin) Prologic DOS but I still can't see how could this be done.

Prologic DOS also uses a decoding table approach, but it can speed up the 
drive CPU to 2MHz. This is done for reading and decoding, of course.

The 8kB extra memory is only usable as 6kB on Prologic DOS, and only 
decoded data is stored there. The remaining physical 2kB are probably used 
as a replacement for the original 2kB memory of the 1541, because this 
becomes unusable in 2MHz mode on the 1541B and 1541-II PCBs.


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Received on 2013-01-14 12:01:04

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