Chip-8 for the RCA Studio II ?

Hi folks,

I know i have not much posted on this blog, that's because i'm trying to finish my OdySim project but from tme to time, i'm trying to hack or mod something for the Studio II or clones. The last mod i've attempted was a "pause" switch and connecting an Atari 2600 joystick in parallel to keypad A. The pause switch works but i haven't fully tested it to see how long it can "pause" without any kind of bugs.

As for the joystick, well it works...BUT..(yeah a big but) by connecting it in parallel to the keypad A of my Studio II, now it's the keypad who doesn't work. That mod too needs to be checked. But orget those for the moment and concentrate on the subject: Chip-8 for the Studio II !! (and Euro clones also).

I had this idea in my head for a long time, something like 12 years now and seems i wasn't the only person who had this idea (later on). The Studio II is based on a series of 1802 CPU's computers (FRED, Elf, Cosmac VIP, etc...) which all of them have many features in commun with the Studio II. If you look at the ELF or VIP computers (just to name these two), both have a interpreter that people could use which is called: Chip-8.

There's a freaking slew of Chip-8 emulators out there (PC, MAC OS, Android, Java...and so on) and even for many game systems like: Sega Master System, Colecovision, Atari Lynx, Game Boy...etc!! but none for the Studio II..so the big question is ...WHY ??!??

The interpreter (or BIOS) that's built-in the Studio II is very similar, in fact uses many Chip-8 references but it is NOT a Chip-8 interpreter which resides in any Studio II or clones. This interpreter is machine language/Chip-8 mix into one especially for the Studio II. There's a "Programming Cartridge" (aka PROM cart) that Aresco published back then that you could program in machine language on any Studio II..cool but then again, why no Chip-8 interpreter ?

If the Studio II is very similar to Chip-8, then why not make a suited Chip-8 interpreter for the Studio II ?? Let's take the VIP as example. the VIP has a ML interpreter that is 512 bytes (1/2K) and is at memory adress 8000, so you need to load the chip-8 interpreter at adress 0000 and Chip-8 games starts at 0200. Simple enough.

So you need a "monitor" (the VIP BIOS) interpreter and the Chip-8 so Chip-8 game can work. Let's say we use the VIP monitor at adress 0000 to 01FF and the Chip-8 interpreter at adress 0200 to 03FF which makes 1024 bytes (or 1K) of codes taken as each interpreters are 512 bytes. So games would starts at 0400 to ... WAIT!!

You need to know that the last 352 bytes are reserved for stack/variables  (from 0EA0 to 0EFF, which equals 96 bytes) and video RAM (from 0F00 to 0FFF, which equals 256 bytes) so games would resides from 0400 to 0E9F (which makes 2720 bytes available).

I tried yesturday a Chip-8 program i've made called "Hello World!) which is a BMP viewer program which looks like this (with Fish 'n Chip emulator - sorry for the small picture, it is 64x32 pixels wide):

 The result was for a first try not too shabby as i saw the Earth image in half and the words were inverted (flipped) with many garbled sprites on screen as i used only the Studio II BIOS+original Chip-8 interpreter (ELF or VIP) with the code of the "Hello World" program. It didn't worked like a charm but at least it's a step in the right direction. Oh and i've put this "bundled" code on a RCA Studio II Multi-Cart available from 'FliP" of Atari Age forums.

Since i'm NO programmer (OK.... I know BASIC and LUA - big Whoop!), is there someone who knows ML/Chip-8 languages for the CDP1802 and could do a Chip-8 intreperter made for the Studio II ? That would be SSOOO AWESOME!!

Because this would extend the game library of the Studio II not to 30 or 40 games but more than 200!! Yup, i'm not joking as i cataloged more than 200 Chip-8 games which this list contains NO alternate versions or program/demos. I have so far 109 Chip-8 games in ".c8" format and i'm missing about 125 Chip-8 games which are still either not typed and saved in c8 format or missing the listing. I will post my list very soon with all the Chip-8 games i've collected so far.