I take that is sarcasm. It was always the plan at the very beginning to add backwards compatability but Nintendo realised they'd make more by selling the Famicom av instead.
It makes not much sense since it was introduced in 1986 to make Apple IIGS retro-compatible with Apple II (1977). If i have not misunderstood. I mean, yeah, Nintendo may take advantage of this chip backward compatibility, but i didnt know it was compatible right in the beginning. Havent seen it in any spanish magazine ..
at 4:11 he says you can plug a master system game directly into the console... "There was nothing inside it (the MS adapter) and all it did was adapt the shape of the cart" The Mega drive has a motorolla 68000 processor but does use a Zilog Z80 for sound and input / output processing. The master system only has a Zilog Z80 for all tasks. The Powerbase Converter (which allows you to play Master System games on the Mega Drive) reroutes the cartridge to use the Z80 processor already in the Mega Drive. But it does contain a Mega Drive ROM image which instructs the Mega Drive on what to do with the input. This means that Master System games will only work on the Mega Drive WITH the powerbase converter. If you try to plug them in directly it is likely you will damage the cart and/or megadrive.
The PBC is mostly passive. I bought a cheap "SMS converter" that has absolutely no BIOS, nothing and it works fairly well. The actual Sega PBC seems to contain only 2 instructions on his "bios" which seems to be needed only for a couple of games if that. [EDIT] Here are the details: http://www.smspower.org/forums/14084-PowerBaseConverterInfo [/EDIT] As I already said the SMS converter I have goes without that and I have not noticed problems per se (again can't exclude a couple of games may have issues). Here: http://www.raphnet-tech.com/products/brd_sms2smd/index.php [EDIT2] In all honesty I only play SMS games with that converter via a MasterED which may as well do the init of the stack properly on its own, I tried R-Type and Ecco with no issue whatsoever. So I am not sure originals would works as well, but said converters have been made for a little and they work reasonably well that not many people complain of the handful of games with issues [/EDIT2] The Genesis cart slot has a couple of signals that can be used to put it in SMS mode, the rest is just mapping of the pins from one cart format/pinout to the other. He is not suggesting that you can literally plug them in directly, he's likely just telling that the Genesis was already fully back compat without the real need of complex adapters (like the 2600 modules for Atari 5200 or the Colecovision which had a complete 2600 system on the board or the Gameboy adapter for the SNES or GBA adapter for Gamecube .... you get the point). So he's right in his statements although I agree he could have added that you need a passive adapter to make it to work due to the different pinout and size.
It's interesting that nothing took advantage of that. The only contemporary NES to SNES converter I know of (the Super 8) used a SOC for its NES/Famicom cloning.
From what I understood from the video, the Mega Drive CPU is 32-bit internal, but 16-bit external (which is awesome!), but the SNES CPU is only 8-bit internal and external? Is this right? If so, what makes the SNES 16-bit?
The MegaDrive CPU is a Motorola 68K (which has a 16bit databus and 32 bit registers). The SNES CPU is a derivative of the WDC 65C816 (which has an 8 bit databus and 16 bits registers). The 65C816 was made as an upgrade to the 6502 (NES uses a derivative of it, but so do many systems of the 80s like the Ataris, Vic20, C64, C16, Plus4) so it can be put in back compat mode (full 8 bit), there's even a version that is pin compatible with 6502 (the 65C802) that was supposed to help in accepting the processor as it was a drop in replacement (needless to say it didn't work out that way). So told it seems that the SNES variant is more powerful than a stock 65C816 with a double data bus and other goodies (http://board.zsnes.com/phpBB3/viewtopic.php?f=6&t=11230). In the end very few systems used the 65C816, the SNES being the only one extremely successful (you can count the Apple IIgs if you really want to), Nintendo must have liked it so much that it's accelerator chip (the SA-1) has another derivative in it (I do not know if this second derivative was fully 16 bits though or what other goodies they packed in it).
Great video. Does the Sega Nomad have that Z80 chip inside of it? I know the power base converter was said to not work with the Nomad but if an adapter was made to fit the Nomad could it be done?
It looks to have some form of a Z80 in it (http://chipmod.blogspot.com/2012/12/sega-nomad-mods-sms-mod-region-mod-lcd.html look at the 5th picture between the cart slot and the RAM, left of the SEGA chip), not sure why it won't work with the Power Base Converter natively (other than size/form factor issues). Note: I'm not an engineer.
Yes the Nomad can play SMS games, remember that the Z80 is used for the music on Genesis/Nomad so it MUST have one. The SMS mod is literally 1 wire connection, without that you can't put the console in SMS mode. http://www.sega-16.com/forum/showth...s-SMS-mode&s=2b486fe7f944307b3c026e7445ce2274
A company here in Japan sells bare master system and mark 3 PCB converters on Yahoo Auctions. They'd fit a nomad for sure.
The 65816 and the SNES variant do not have a "double data bus". I have no idea where you were told this but this is entirely false. The 65816 including the variant in the SNES has an 8-bit data bus. The 65816 does have a 16-bit ALU internally. But the external memory goes through an 8-bit bus. If it has a 16-bit bus width, SNES Cartridges would require 8 more pins for those signals. Check the cartridge pinout, there are no D8 to D15 signals. No one who would know has said in public the answers behind why Nintendo did the things they did with the SNES. Rumors exist that they considered using the 68000 CPU instead of the 65816. And then of course there is the rumor about backwards compatibility being considered. But the only things backwards compatible in the SNES with the NES is the CPU can run the program code and the controller port communication is compatible. But the NES CPU was not a standard 6502. It generated audio which the SNES CPU could not do. More importantly the graphics hardware is not at all compatible with the NES. If they had wanted to make it backwards compatible it would have meant including very costly amounts of die space (chip space) on the CPU to add what was needed for the NES and it would have also needed a whole NES PPU plus the cartridge port would have needed way more pins to allow the PPU bus connections with the Cartridge. It made far more sense to just keep selling NES and Famicom systems for those wanting to play those games.
Agreed, "double data bus" was my misinterpretation but: http://board.zsnes.com/phpBB3/viewtopic.php?f=6&t=11230 and http://wiki.superfamicom.org/snes/show/Memory+Mapping show there's double address bus which makes it highly non standard. My main point is that the SNES CPU is more capable than a stock 65816 https://en.wikipedia.org/wiki/Ricoh_5A22 Sorry about the misguided quote on double data bus (I didn't mean 16bit either I thought there were 2 separate 8 bit data buses instead of a secondary 8 bit address bus)
