Genesis On A Chip (GOAC)

[Red5]

Hi DevSter (& everyone else),

A few of us over at the Doom Portables forum ( www.benheck.com/Games/Videogame%20Forums.htm ) were/are looking at the new Genesis On A Chip (GOAC) from Radica games with the aim of making it into a portable Genesis (a Nomad II if you will). You can find a review of the unit, including a photo of the main circuit board at Lik-Sang ( www.lik-sang.com/news.php?artc=3477 ).

As you can see from that photo the 32MBit rom is stored on a little daughter board, the idea is to remove this and solder an Genesis cart connector in it's place so that it can then play original carts, however it uses 44Pins so I'm a bit stumped as to proceed...

Is it a custom chip, in which case I'm probably screwed, or is it a "whole cart" on there (ie a "42Pin Chip" plus 2 "extra" pins for +5V and GND) in which case it may be possible, but where to start? Any clues/suggestions and has anyone else attempted this yet.

Red5

[Tom Maneiro]

Are you Red5 from Genesis Project?

[Red5]

Wow, that's twice this week that someone's asked me that on a forum! And to answer your question... Yes it is, although it would now be more accurate to say "Red5 - formally of the Genesis Project". ;D

[oompa loompa]

the rom, and the cpu parts are definitely custom chips, molded right onto a pcb instead of a classic plastic packaging holding them in and goin to some pins. It wouldn't be trivial to determine what pins do what. you'd need to do lots of guessing

a 32mbit memory in 44 pins just requires:
2 - vcc, gnd
16 - data i/o
21 - address
2 - control

which leaves 3 pins undefined x.x, which are actually connected, and used by the unit. these could be connected to gnd or vcc, or they could be banking pins.

you could possibly find more technical info on this mini by finding the patent on it, if it exists =)

hey, this is news to me, i though there was another mini sega genesis built a while ago, which held all its hardware in the controller. i dunno, it might not be a sega genesis after all =P, i gotta find one of these "GOAC"s on ebay. it'd be a really neat toy =D

[Red5]

Damn, I suspected this wasn't going to be easy

There was another GOAC done a few years ago called the Mega-Drive 3, you can find a review I wrote for it here: segaclone.emucamp.com/clones/antony/megadrive3.htm

That uses a 42Pin chip, hovewer I've never dared tamper with it because when you open it up the constuction is a little poor. The main processer looks like it's been "rescued" (badly!) from a second hand Genesis MkII, and all the soldering looks like it's been done by a blindfolded army of chimps! I'm surprised it even works to honest.

The new unit made by RADICA under their "PlayTV" brand and is available at high-street retailers right now for £20 (I think its $30 in the good 'ol US of A). In the UK look at Argos and Toys 'R Us, for America Toys 'R US and probably places like Wal*Mart etc.

[oompa loompa]

hehe the wal-mart was my next target to find this thing =D

and this is what i would do to determina the pin out for that rom chip. i would find the power connections first which wouldn't be so hard. then i'd desolder that sucker off and power up the genesis to see which pins are going to be outputs. we'd expect that if the 68k ouputs data, then that's an address line, or control. then i'd hook up the rom chip and see which pin puts out a current. it may be tricky because usually the data lines are in hi-z when the chip is disabled. but a hi-z still puts out a little current. oh and the chip enable line, or output enable, you can put a pin low, and then some other pin should source a good amount of current.

to see what bits the address or data are, i'd just place everything on an i/o system and change the values here and there until i get a pattern that looks like a rom =D

[Tom Maneiro]

like attach a hw debugger?

[Red5]

OMG that sounds way complicated, which is why I didn't attempt it Having seen DevSter's "Genesis computer" I figured if anyone had the knowhow to do this it'd be him which is why I posted here ;D

[oompa loompa]

;D i'll really try to get one of these on my hands. but i wouldn't pay no $50 for it though =D, i'd go for it if it were $30 cause i can go get a regular genesis for $10 at goodwill =P. plus, "chip on board" packages don't have a very long lifespan, maybe ~5 years if you don't drop the thing as much =)

[Red5]

Toys 'R Us currently has it listed on their site for $25:

www.amazon.com/exec/obidos/tg/detail/-/B0002E7C96/qid=1101650422/sr=1-24/ref=sr_1_24/103-8686707-6593410?v=glance&s=toys&m=A3UN6WX5RRO2AG

Wal*Mart also has it listed for the same price (give or take a few cents):

www.walmart.com/catalog/product.gsp?product_id=2697004

You should be able to pick it up in most retail stores for $25 to $35 (I think $35 is the RRP). The $50+ from Lik-Sang was for the import version before it became officially available in the UK and USA.

Over on the Portables of Doom forum (see link in my first post) SegaSonicFan has managed to decipher a couple of the pinouts (mostly grounds), but has pretty much come to the limits of his knowledge as far as that goes so any help from you DevSter would be appreciated

Red5