Re: Fast GCR decoding?

From: silverdr_at_wfmh.org.pl
Date: Sun, 20 Jan 2013 18:01:32 +0100
Message-Id: <87396EF4-A467-4E7F-B4D6-4B9EF0759A64@wfmh.org.pl>
On 2013-01-16, at 10:21, Michał Pleban wrote:

> Hello!
> 
> After some private discussion and a night of thinking, this morning I
> wrote the code that decodes GCR on the fly ;-) Decoding 5 GCR bytes into
> 4 output bytes takes me 112 cycles, including storing the bytes with STA
> (output), Y + INY. This does not, however, include BVC / CLV
> instructions for reading from VIA, as the code should rather be run on
> the computer (it requires nearly 10 kB of tables).

[...]

> ; Total = 112 cycles
> ; Data = 38 tables (9.5 kB)

Hehe.. now I only need time to understand this and write program that will generate those 38 tables so that we can verify how/whether it actually works :-) But if there are no major errors then it might indeed be the fastest thing we saw so far!

-- 
SD!
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Received on 2013-01-20 18:00:04

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