Re: [stella] 12 chars/line!? (was: re: optimizations; Call forsuggestions)

Subject: Re: [stella] 12 chars/line!? (was: re: optimizations; Call forsuggestions)
From: Piero Cavina <p.cavina@xxxxxxxxxxxxx>
Date: Thu, 25 Sep 1997 22:05:22 +0100
At 10:48 -0700 24-09-1997, Greg Troutman wrote:

>> That would allow 48/4=12 charachters per line (without flicker)!
>> Can it be done?
>You mean a half-width font, instead of hard-coded graphics?  Sure.  Very
>problematic though.  There is not enough time within the six-digit trick
>to read and combine the 4 bit parts into one graphics register.  So, it
>has to be done in RAM beforehand, and that means 30 bytes for one 5
>scanline high line of text.

Yes, it's exactly what I was thinking.

>You can't very easily re-use that RAM area
>for drawing multiple lines of text in the same frame, because the loop
>that would combine 12 4-bit characters into 6 one byte graphics data,
>five scanlines high, would take well over a thousand cycles, I think,
>producing as many as 20 blank scanlines while you busily reload that RAM

Are you sure it would take so much time?
The font could be stored in this way...:

; letter "A"

byte %01000100

ie - the same 4-bit character twice in 1 byte, so that combining two of
them into 1 byte can be done without shifting bits...


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