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Regarding flash carts for megadrive

Discussion in 'Genesis - SCD - 32X Dev' started by Denis, Mar 5, 2002.

  1. Denis

    Denis New Member

    I have such flash cart.

    it have onboard TWO ROMs, marked as:

    ST 88844S

    M27256FI

    (i.e. - total 512kb??)

    On this cart now is flashed CDX (from Eidolon's Site).

    Is it possible to replace those two roms with anything bigger then 512kb (i.e. to flash at least Knuckes Chaotix 32x - 3mb or Star Wars Arcade 32x ~2,5mb (20Mbit))??

    Thanks!
     
  2. IceDigger

    IceDigger Founder Staff Member

    those are no flash roms, but eproms, as far as I know.. and in fact only 32 kb each.

    the main problem is that these have only 28 pins, it would take quite some hacking and re-wiring to get them to be 32 pin, plus, you need FOUR chips to achieve more than 16 mbit on a cart.

    also, if your cart edge connector doesn't have all pins, you can forget it anyways.

    I don't think that cart will really do you any good, unfortunately.

    where'd you get that from anyways, and what was it before?
     
  3. Denis

    Denis New Member

    Thank you Arakon!

    About eproms - yes they are really 28 pins! Btw, im not any good with hardware :) but in case of megadrive/genesis carts - what the difference between 28/32 pins (sorry if it's a very dumb question - but im very bad with real hardware)?

    And about FOUR chip - why four? if im not wrong, i heard that there exits flash roms at lest with 32mbit on single chip?

    So, possibly, this cart is really useless? :(

    about origin of this cart: it was maked for me in one little firm (gone now) which does TV test/tune carts for NES and Megadrive (i just went to them and ask them to make cart with my own ROM dump - which was CDX rom from Eidolon).
     
  4. Denis

    Denis New Member

    Oh, btw. Is there any instructions/manuals on the net, covering the building of flash cart for md/genesis?
     
  5. ExCyber

    ExCyber Staff Member

    Yeah, I think they have normal parallel flash up to 256mbit or so now (there are bigger ones intended as mass storage, but they're useless for making an MD/32X cart). The main problem with those devices is that they're not easy to solder (typically they're only available as TSOP or BGA - TSOP requires practice and sometimes special techniques to solder, and BGA is virtually impossible to solder without an expensive hot air tool), and you'd have to make your own circuit board to fit them without putting wires on every pin.
     
  6. IceDigger

    IceDigger Founder Staff Member

    plus, a single 32 mbit flashram is most likely gonna cost a shitload, and have a totally different pinout (and number of pins for that matter), so you'd have to actually create your own pcb for it too.
     
  7. ExCyber

    ExCyber Staff Member

    Not really. In fact, depending on the state of the market and which specific devices you choose, it can be significantly cheaper than four 8Mbit memories. Come to think of it, I think a bigger problem would be finding one with 5V-tolerant inputs...
     
  8. Denis

    Denis New Member

    Thank you guys!

    Btw, ExCyber - do you have already wroted any instruction on hacking (i.e. replacing eproms) on bootlegs carts? It'll be a great help :)

    Is there any resources on net about homemade flash/eprom carts for md/gen?

    Thanks
     
  9. ExCyber

    ExCyber Staff Member

    Nope... the way I did it with Arakon was that we met on IRC - he had the cart and a continuity tester, I had the documentation (cart and standard logic pinouts) to work from. The specific modifications that need to be made for a cart depend on the design of the cart, but for a cart with 4 standard pinout 8-bit ROMs, you need to:

    1) Wire any extra address pins to the ROM sockets to match the size you want to use for the replacement ROMs.

    2) Move (i.e. cut and rewire) a logic connection so that the low/high bank switching works correctly with the altered cart size.

    Neither of these mods needs to be made if you simply want the same capacity as the existing cart - just desolder the originals, drop the replacements in and you're set.

    By the way, have you given any thought as to how you're going to write the replacement ROMs? A cart like this requires having separate burner hardware to write the ROMs that you put into the cart...
     
  10. Denis

    Denis New Member

    Thank you. So, firstly, i need to get any 32mbit bootleg md/gen cart.

    >>By the way, have you given any thought as to how >>you're going to write the replacement ROMs? A cart >>like this requires having separate burner hardware >>to write the ROMs that you put into the cart...

    If you mean just writing to roms - i think it's not a problem (there are exits firms which burns various roms with programmer).

    But i think, you also means something about splitting rom dump image to pieces as number of roms onboard the cart? (i.e. if we have 4x8mbit roms on cart we need to propertly split 32mbit game image to 4 parts)? No, i dont figured yet how to do it...

    But, i headr about some "secret" programm from Eidolon - is it such thing??
     

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