Re: [hatari-devel] defaulting to SMALL_MEM

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 18/02/2022 à 21:33, Thomas Huth a écrit :
> Am Thu, 17 Feb 2022 11:14:25 +0100
> schrieb Nicolas Pomarède <npomarede@xxxxxxxxxxxx>:

> > That is, instead of allocating STRamEnd bytes for STRam[], we
> > allocate STRamEnd + SCREENBYTES_LINE*10 bytes and fill this extra
> > space of SCREENBYTES_LINE*10 bytes with 0.
>
> After thinking about this for a while, I agree, it's like the best
> solution to add some margin to the allocation for this instead, to
> avoid that the code gets too ugly and to avoid regressions with the
> performance of the rendering functions.
>
> But shouldn't we rather allocate NUM_VISIBLE_LINE_PIXELS *
> NUM_VISIBLE_LINES / 2 bytes instead? ... in case a program sets the
> memory base to the very end of the RAM and then does some fullscreen
> tricks?

yes, SCREENBYTES_LINE*10 was an example, but a proper counting should be 
done.
In all cases it would just add less than 100 kB for a whole screen, so 
even if we round it to 100 or 200 kB if we're too lazy to do a proper 
counting of bytes, it's quite negligible.

now if we want someday to really emulate what happens when video pointer 
goes just after a max of 512 kB of RAM for example, then we will need 
some special cases to render such lines and to display the latest word 
seen on the bus ; but that's a really different story :)

> Anyway, we should add a proper comment to the allocation, otherwise
> we'll wonder in a couple of years why we did that change ;-)

that's quite possible :)

Nicolas