[stella] FIFO memory idea.

Subject: [stella] FIFO memory idea.
From: R Mundschau <rmundsc@xxxxxxxxx>
Date: Sat, 18 Jan 2003 22:56:38 -0600
I'm no hardware expert, but it seems to me that it would be a rather simple
design to make an Atari 2600 cart with a FIFO chip in it.   You would need
decode logic to place the read and write ports in memory.  I am thinking
that the write port could overlap with the 4K ROM space.  I'm not sure where
the best place would be to map the read port, I need to look at the Atari
schematics again.

FIFOs come in different sizes 1K, 4K, 8K, etc. but they all have the same
footprint so a single circuit solution should work for all sizes (ithink).

Using software you could implement a primitive disk drive or sorts. Divide
the FIFO into blocks of 16 or 32 bytes.  Keep a pointer to the block at the
head of the queue.  And a buffer equal to the block size in RAM.

Then you need a routine to read out the head block.  If its not the one you
want, stuff it back in.  Loop until you reach the block you want.  By
writing new data into the back of the queue while the target block is at the
head of the queue you would effectively write to the disk replacing the
existing block which would be pushed out the front of the queue and be

I think this would be a great way to implement an RPG type game on the 2600.
You could store lots of room/monster/character/game-state information in the

Another possibility is to have a FIFO to store a stream of "rendered" video
information which can then be dumped onto the screen.  A pair of FIFOs would
allow you to "render" one such frame while another is being displayed.

Am I nuts?
Rob M  

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