Thoughts on Sega's "clean" hardware design aspects . . . and the Saturn.

[Kamahl]

Sega made some very dumb decisions with the genesis.

The way the chip is designed it can handle 128 colours just fine (separate 4 palettes for sprites and another 4 for backgrounds), but possibly for space reasons Sega put CRAM inside the chip instead of external to it, and maybe that's as much as they could manage? I dunno, I have no idea how CRAM works.

The 512 colour master palette is another brain teaser. The chip already reads 12 bits so why not expand the palette to 4096 colours? We'll never know.

The difference between 64/512 and 128/4096 is huge. Even just changing either is huge, look at this 64/4096 Amiga image:


(From the game Agony, drawn by Franck Sauer)

And the Amiga was rather limited in the second set of 32 colours (they all had to be half-bright versions of the first 32)

Then there's the audio which seems to be designed to make PCM playback as difficult as possible. Serial banking register? Why???? 100+ cycles to change banks on the Z80 side. Oh and since the Z80 is supposed to be used for audio, lets not connect the audio chip timers to it, that would make too much sense.

If not for the two stupid decisions above everyone and their mother could have made mod players for the genesis. That would have made western developers lives so much easier (porting Amiga soundtracks straight over for example).

Just these two minor changes in graphics and audio would have made the genesis much more powerful. Stupidly so.

[Bibin]

I still think the decision to use 9-bit color and 12-bit color was a last minute compromise or design problem. Look at how CRAM is organized, and how the LSB of each nybble goes unused. I would bet that was supposed to be a fourth bit at some point.

[tomaitheous]

I still think the decision to use 9-bit color and 12-bit color was a last minute compromise or design problem. Look at how CRAM is organized, and how the LSB of each nybble goes unused. I would bet that was supposed to be a fourth bit at some point.

Well, think about this way too; it's easier to work on the R/G/B individual level when it's segmented by nybbles. The PC-Engine has 9bit color entries too, but they are bit packed into a 9bit WORD. It's more of a pain to modified each individual element. So from that perspective, it makes sense to keep a 9bit value in a 12bit format with the LSBits having no effect. Hudson could have wired the lines like that too, but didn't. On the PCE, you can read back any or all of CRAM. Can't remember if this is true on the Genesis as well (read cram values).

[Kamahl]

Yeah it's most definitely odd. It's weird looking at the genesis and seeing how very minor changes could wield such massive gains. The SNES is the opposite, a totally over-engineered mess.

it's easier to work on the R/G/B individual level when it's segmented by nybbles. The PC-Engine has 9bit color entries too, but they are bit packed into a 9bit WORD. It's more of a pain to modified each individual element.

Meh, either one still requires shifting around bits and using masks. They should have put those bits to some use.

EDIT: It just occurred to me we're talking about the company that made the genesis model 2 and thought the 32X was a good idea. Everything makes sense now, carry on.

[Bibin]

Well, think about this way too; it's easier to work on the R/G/B individual level when it's segmented by nybbles. The PC-Engine has 9bit color entries too, but they are bit packed into a 9bit WORD. It's more of a pain to modified each individual element. So from that perspective, it makes sense to keep a 9bit value in a 12bit format with the LSBits having no effect. Hudson could have wired the lines like that too, but didn't. On the PCE, you can read back any or all of CRAM. Can't remember if this is true on the Genesis as well (read cram values).

Sure, but you can pack it into nybbles in the first 3 bits. In the Genesis, we use the upper 3 bits and lowest bit of the nybble is unused. It's really weird this way. Why not have the MSBs have no effect?

[evilevoix]

Very good thread a lot of new info here for me.

[TrekkiesUnite118]

EDIT: It just occurred to me we're talking about the company that made the genesis model 2 and thought the 32X was a good idea. Everything makes sense now, carry on.

And that's not even getting into the mess that was the Saturn. I'd imagine this was the reaction most devs had reading through the manuals:

[Kamahl]

I had that reaction trying to understand some features of the SNES . Everything and the kitchen sink design that bloody machine. It sure is powerful though, can't deny that.

Part of me wishes Sega had been a bit more ambitious with the genesis. It just feels like they didn't really give it their all...

Ditch the Z80, the SN, mode 4 and shadow/highlight, they're all wastes of silicon (maybe not the Z80, but still). The SN could have been put in the power base converter, and mode 4 could have been replicated in a Super Game Boy kinda way. All that extra space and money could have been put into more colours, proper PCM or sprite scaling.

[TrekkiesUnite118]

I think some of those issues could have been resolved though without removing the SMS modes. PCM Playback as I understand it boils down to not hooking up the timing lines and serial banking. Would fixing those make SMS compatibility not work or something?

Also the SN I think is fine, it's used quite often in Genesis games to give additional channels. I don't see much benefit to ditching it. Color though I think even if Sega stuck with the 4 palettes and 9-bit RGB, the color set up could have still been decent had they just put the ability to expand it through the cart and expansion slots. That way games that needed more color could have it, and add-ons like the Sega CD could have expanded it.

As I understand it those wouldn't be that radical to implement as the system was, so I don't think they really would have needed to nix a whole lot to do it.

[Kamahl]

They didn't need to axe the features I mentioned to implement the rest. They're simply things that waste space on the machine (and money) that could have been put to better use. Really as soon as you need an adapter, what's the point of builtin compatibility? Any of the 3 SMS components they cut (Z80, SN, VDP compatibility) that they put into the power base converter instead is more space (and money) on the genesis for other things.

[TrekkiesUnite118]

They didn't need to axe the features I mentioned to implement the rest. They're simply things that waste space on the machine (and money) that could have been put to better use. Really as soon as you need an adapter, what's the point of builtin compatibility? Any of the 3 SMS components they cut (Z80, SN, VDP compatibility) that they put into the power base converter instead is more space (and money) on the genesis for other things.

True, but I think at the very least the SN and Z80 made sense to be in there. The Z80 works well as a chip to control the YM2612, and the SN adds some nice additional channnels for audio when used properly. Some of the best tracks on the Genesis just wouldn't sound right without their PSG channels.

[001]

While I do agree with the technical improvements you guys are proposing, keep in mind, when they were designing the Megadrive, it only had to technically blow the NES out of the water. Sega's success wasn't a sure thing. The NES still had a tremendous library of well known games, a monopolistic stranglehold on third party developers and people referring to home video game systems as 'nintendos'. Nintendo was the 800 pound gorilla at the time. SMS compatibility was used to somewhat address that disadvantage:

[Kamahl]

Well sure, I'm not saying don't have backwards compatibility at all, I'm saying that parts of it could be in the power base converter (which was necessary anyway). If you need to buy extra crap to play older games, put the necessary compatibility stuff in the extra crap.

I also disagree that the SN was in any way necessary on the genesis. All its channels combined usually amount to a single extra instrument in the song. I'd much rather have an YM2151+PCM or YM2608 instead of the YM2612+SN combo. Some of the most impressive tracks on the genesis don't make use of the thing at all.

I'm mostly whining about the SN because it's on the VDP, alongside the master system compatibility. Making the chip smaller and simpler would probably have made it a no brainer to add extra colours (the chip easily supports 128 colours by design).

The Z80 could have remained as a sound controller sure, I'd even simplify things further and make it the *only* way to control sound.

[001]

I understand and I agree that what you are saying, in hindsight, would have been the best thing to do probably, given the way things actually played out. I'm only defending their design choices for compatibility because I think if they placed the logic in the PBC, they would be hard pressed to sell it that cheap (or give it away for free) if developer support never materialized on 16-bit games for the Megadrive. That was a very real possibility back then. The way they designed it, people had a seemingly cheap way of tapping into the master system's library.

[Kamahl]

Half the price of a game is most definitely NOT cheap . What kid would think "I should convince my parents to get me this $35 thing plus this outdated 8bit $60 game" vs "get me ghouls and ghosts, now!"