Why are Genesis' specs reduced in 256 mode?

[Kirk_Johnston]

The Genesis can display 80 sprites onscreen and 20 16x16 sprites per scanline in 320 mode, so what possible good reason could there be for reducing those specs to 64 sprites onscreen and 16 16x16 sprites per scanline in 256 mode?

 

I know the majority of Genesis games are 320 anyway, so this isn't a huge deal in the grand scheme of things, but why not keep the higher numbers in 256 mode too, which would have allowed the Genesis to compete much more effectively with SNES in those areas when a developer did decide to make their Genesis game in 256 mode for whatever reason.

 

I mean, when both machines are running in 256 mode, the SNES can put 128 sprites onscreen and 17 16x16 sprites per scanline, whereas the Genesis can put 64 sprites onscreen and 16 16x16 sprites per scanline, so it just seems strange to deliberately limit it in this particular mode when it can obviously do more.

 

Does anyone know the reasoning behind this?

Edited July 30, 2022 by Kirk_Johnston

[Asaki]

I'm pretty sure I've read a thread about this "feature" before, maybe here, maybe at Sega 16...I'd have to search to find it, though.

[+Gemintronic]

I couldn't find reference to this limitation after googling, searching Sega-16 and official documentation .PDFs. 

 

Can you link the source Kirk_Johnston?  My hunch is that you might want to write your own test program in assembly, C or SecondBASIC to verify.

[Kirk_Johnston]

Well, a quick Google search brings up the following links:

 

https://segaretro.org/Sega_Mega_Drive/Sprites

 

https://wiki.megadrive.org/index.php?title=VDP_Sprites#H32_mode

 

https://www.sega-16.com/forum/archive/index.php/t-14387.html#:~:text=In 256 pixel mode you,And total of 64 sprites.

 

http://www.gamepilgrimage.com/content/sega-genesis-vs-super-nintendo#footnote21_no4temg

 

And I know I've seen it in a few other places too.

Edited July 30, 2022 by Kirk_Johnston

[M-S]

If I remember correctly that would have made the Genesis as expensive as a Neo Geo, so they did it in order to reduce the price.

[Chilly Willy]

The reason the stats drop from 40 tile to 32 tile mode is because the console physically lowers the clock the VDP is using to fetch data between the two modes. Slower clock equals less fetch slots which equals lower stats. Actually, it's really the other way around... in 40 tile mode, they raise the clock to fetch the extra data needed to display more pixels per line, and as a result, the stats go up.