Re: Fast GCR decoding?

From: silverdr_at_wfmh.org.pl
Date: Tue, 15 Jan 2013 15:38:04 +0100
Message-Id: <0BEA9356-67EA-4760-8584-E910418F1E8F@wfmh.org.pl>
On 2013-01-15, at 15:27, Michał Pleban wrote:

>> According to my count 186 cycles, although the answer is somewhat more difficult than that: I /would/ need 186 cycles, provided that I would read the incoming bytes off the VIA and be able to decode them on the fly (and the routine is bug-free :-). Since with 40+ cycles on most bytes I can't do it on the fly, I need to read/decode off-the buffer. That would add cycles and put me in the range of 200+ cycles, which is about the same as what 1571 routines do off the buffer.
> 
> Another question: what is the maximum size of lookup tables you can use?

I have 8KiB in the drive. I can also shift decoding to the host, which means I can theoretically go over 8KiB if needed. But of course I still need some room left for other things ;-)

So - I'd say as a proof of concept I would go for any size that can fit in 64KiB along with the code and I/O areas.

For practical use the size has to be reasonable of course but let's not limit it at this moment.

-- 
SD!
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Received on 2013-01-15 15:00:36

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