Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
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Message: 708
Author: john_elliott_uk
Date: 09/09/2000
Subject: Re: About JSWED
<< What if it were possible to transfer
data taken up by rooms in JSW128 into free space for
guardians, sprites or other features >>
The
basic unit of memory in JSW128 is a "page" (256 bytes).
This will hold one room, 8 sprite frames or one
quarter of a guardian table.
Because of the way
the 128's memory works, anything in the extra memory
(in the current JSW128 this means the rooms and the
title screen) must be copied into normal memory before
use. This isn't a problem for a room, as JSW48 copied
rooms anyway, so JSW128 can do the same. For guardians
it isn't particularly problematic either, because
they get copied from their guardian table to normal
memory; so guardian tables could be put in extra memory,
though they aren't at the moment. Sprites aren't copied
around.
JSW128 stores rooms in the extra memory, and
sprites and guardians in standard memory. This isn't the
only solution possible. For example, I can imagine a
system where each room has its own 8-entry guardian
table (64 bytes); you'd then have 204 rooms, a
different set of guardian patterns in each, and an extra 2k
for sprites in main memory. Sprites themselves are
somewhat bulky, and there aren't any existing buffers for
them; you'd have to sacrifice sprite pages in main
memory to make room for the buffers. Editing might be a
bit nightmarish too.
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