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What's so special about the 68000?

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mr_bigmouth_502
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01 Feb 2015, 5:13 am

Tollorin wrote:
Could the SuperFX chip really help to put more actions on screen!? It was mostly used for polygonal graphics and some special effects; the SA1 chip, used in Super Mario RPG and acting as a second CPU for the snes, make more sense for such a use to me. Though I don't know that much about electronics...


The SuperFX chip was actually a small 32-bit RISC CPU, not just a graphics chip. It allowed for polygonal 3D graphics and true sprite scaling and rotation (Mode 7 was ONLY for backgrounds), but it could be programmed for other things as well.

Thinking about it now, I'm not entirely sure why they decided to come up with the SA-1 when the SFX was already a thing. Maybe it was just less expensive, or easier to program for, as it's primarily a higher-clocked version of the stock SNES CPU...



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17 Jul 2016, 10:41 pm

https://m.youtube.com/watch?v=E83CEwYhE0E

There! Look at what a 3.58 Mhz 65816 could do when it is programmed by somebody who isn't trying to sabotage the SNES.



mr_bigmouth_502
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18 Jul 2016, 3:08 pm

I'll admit, I didn't actually know you were an SNES coder until I saw your name on the video. What systems do you have experience coding for? Also, what emulator are you using to record your videos with?


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19 Jul 2016, 12:43 am

Just the SNES so far, but I've done research on other systems. Most SNES games look like they were programmed C, based on snippets of code from dissassembled games. I did all my programming in ASM, and CPU speed is almost never a problem for me.



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19 Jul 2016, 10:52 am

Aaendi wrote:
Just the SNES so far, but I've done research on other systems. Most SNES games look like they were programmed C, based on snippets of code from dissassembled games. I did all my programming in ASM, and CPU speed is almost never a problem for me.

That's actually kind of surprising. You'd think most games from that era would be coded in pure ASM, since the compilers that existed for higher level languages at the time weren't up to snuff.


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19 Jul 2016, 1:05 pm

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That's actually kind of surprising. You'd think most games from that era would be coded in pure ASM, since the compilers that existed for higher level languages at the time weren't up to snuff.


Which is exactly why the SNES was known for it's slowdown. Nobody knew how to program the 65816 in ASM, so they went with C instead, even when it was horribly inefficient.

You could tell by looking at codes that it wasn't written directly in ASM because:

-They never directly use variables stored in memory. They always move them to a temporary memory space before using them.
-They never use a register twice in a row without loading and storing from memory, even when it's the same variable.



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19 Jul 2016, 1:29 pm

Aaendi wrote:
Quote:
That's actually kind of surprising. You'd think most games from that era would be coded in pure ASM, since the compilers that existed for higher level languages at the time weren't up to snuff.


Which is exactly why the SNES was known for it's slowdown. Nobody knew how to program the 65816 in ASM, so they went with C instead, even when it was horribly inefficient.

You could tell by looking at codes that it wasn't written directly in ASM because:

-They never directly use variables stored in memory. They always move them to a temporary memory space before using them.
-They never use a register twice in a row without loading and storing from memory, even when it's the same variable.

That's some pretty interesting stuff there.

I know that the graphics processor and audio chip were used to compensate for slower CPU clock speed on SNES. That's why most SNES games use a higher color palette and PCM sampling for all the music with ease.

Sega Genesis has some power and interesting tricks up its sleeve, though.

Generally, it could process 64 colors per frame (SNES could do 256, I believe).

But if you look at the Mickey Mouse moose chase scene, they figured out how to process a little over a thousand colors per frame with a programming trick:


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mr_bigmouth_502
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19 Jul 2016, 6:45 pm

Aaendi wrote:
Quote:
That's actually kind of surprising. You'd think most games from that era would be coded in pure ASM, since the compilers that existed for higher level languages at the time weren't up to snuff.


Which is exactly why the SNES was known for it's slowdown. Nobody knew how to program the 65816 in ASM, so they went with C instead, even when it was horribly inefficient.

You could tell by looking at codes that it wasn't written directly in ASM because:

-They never directly use variables stored in memory. They always move them to a temporary memory space before using them.
-They never use a register twice in a row without loading and storing from memory, even when it's the same variable.

But isn't the 65816 basically just a 16-bit 65c02? Why would the 65816 be so much more difficult to program?


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mr_bigmouth_502
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19 Jul 2016, 6:54 pm

marcb0t wrote:
[That's some pretty interesting stuff there.

I know that the graphics processor and audio chip were used to compensate for slower CPU clock speed on SNES. That's why most SNES games use a higher color palette and PCM sampling for all the music with ease.

Sega Genesis has some power and interesting tricks up its sleeve, though.

Generally, it could process 64 colors per frame (SNES could do 256, I believe).

But if you look at the Mickey Mouse moose chase scene, they figured out how to process a little over a thousand colors per frame with a programming trick:


Holy s**t. Those are some lush colors. 8O Everything moves so smoothly too. Who woulda thunk a Mickey Mouse game would show off the Genesis' capabilities so well?

The sound could be better though, it's pretty typical western FM synth. If SNES developers were lazy with their coding, Genesis developers in the west were lazy with their sound, using the notoriously bad GEMS engine with randomly-generated FM patches (!) instead of actually learning the intricacies of FM synthesis.


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19 Jul 2016, 7:57 pm

mr_bigmouth_502 wrote:
marcb0t wrote:
[That's some pretty interesting stuff there.

I know that the graphics processor and audio chip were used to compensate for slower CPU clock speed on SNES. That's why most SNES games use a higher color palette and PCM sampling for all the music with ease.

Sega Genesis has some power and interesting tricks up its sleeve, though.

Generally, it could process 64 colors per frame (SNES could do 256, I believe).

But if you look at the Mickey Mouse moose chase scene, they figured out how to process a little over a thousand colors per frame with a programming trick:


Holy s**t. Those are some lush colors. 8O Everything moves so smoothly too. Who woulda thunk a Mickey Mouse game would show off the Genesis' capabilities so well?

The sound could be better though, it's pretty typical western FM synth. If SNES developers were lazy with their coding, Genesis developers in the west were lazy with their sound, using the notoriously bad GEMS engine with randomly-generated FM patches (!) instead of actually learning the intricacies of FM synthesis.
Well, true. Decent US Genesis music was hard to come by. Making good FM patches takes time and skill, and imagination. Surely you've heard the Tim Follins "Time Trax" beta soundtrack for Genesis. It only uses FM with no DAC sampling or PSG. As a Sega Genesis musician myself, I can tell you this soundtrack is absolute genius!


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20 Jul 2016, 2:58 am

Time Trax has some really impressive music. :D It really shows off what the Genesis sound chip is capable of.


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20 Jul 2016, 1:28 pm

mr_bigmouth_502 wrote:
Time Trax has some really impressive music. :D It really shows off what the Genesis sound chip is capable of.

Here is a proof concept of Star Fox running on a Sega Genesis. There is no need of an extra chip in the cartridge:



Obviously, there is gradienting with the polygon shading (64color limit), but still this is not bad at all.

There is a better theme song for Genesis that I made the orchestra hits for:

https://drive.google.com/file/d/0B2C16041iMhgbGpWY1RnNnpJZUU/view?usp=drivesdk

This track uses only Genesis FM and PSG. NO sampling.


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mr_bigmouth_502
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20 Jul 2016, 8:41 pm

marcb0t wrote:
mr_bigmouth_502 wrote:
Time Trax has some really impressive music. :D It really shows off what the Genesis sound chip is capable of.

Here is a proof concept of Star Fox running on a Sega Genesis. There is no need of an extra chip in the cartridge:



Obviously, there is gradienting with the polygon shading (64color limit), but still this is not bad at all.

There is a better theme song for Genesis that I made the orchestra hits for:

https://drive.google.com/file/d/0B2C16041iMhgbGpWY1RnNnpJZUU/view?usp=drivesdk

This track uses only Genesis FM and PSG. NO sampling.

I'll admit, I like the version of the song in the video better. That one just blows me away with how awesome it is. But your version is a commendable effort too, especially since you didn't use any samples. ^^

But one thing I've noticed is that some of the better Genesis music out there tends to use the PSG in tandem with FM. I'm not a big fan of the PSG sound on its own, like on the Master System, but it works well alongside FM synthesis since it's hard to do square waves in FM.


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21 Jul 2016, 6:54 pm

marcb0t wrote:
mr_bigmouth_502 wrote:
Time Trax has some really impressive music. :D It really shows off what the Genesis sound chip is capable of.

Here is a proof concept of Star Fox running on a Sega Genesis. There is no need of an extra chip in the cartridge:



Obviously, there is gradienting with the polygon shading (64color limit), but still this is not bad at all.

There is a better theme song for Genesis that I made the orchestra hits for:

https://drive.google.com/file/d/0B2C16041iMhgbGpWY1RnNnpJZUU/view?usp=drivesdk

This track uses only Genesis FM and PSG. NO sampling.

While it's impressive, the frame rate is lower that the already low frame rate of Star Fox and there is less objects on screen. It may end up too gimmicky to make a good game. It certainly can't be a easy task to make a good 3D game on the Genesis without a extra chip, as if it would have been easy Sega would have put more 3D in their games to impress players.


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22 Jul 2016, 1:09 pm

Tollorin wrote:
marcb0t wrote:
mr_bigmouth_502 wrote:
Time Trax has some really impressive music. :D It really shows off what the Genesis sound chip is capable of.

Here is a proof concept of Star Fox running on a Sega Genesis. There is no need of an extra chip in the cartridge:



Obviously, there is gradienting with the polygon shading (64color limit), but still this is not bad at all.

There is a better theme song for Genesis that I made the orchestra hits for:

https://drive.google.com/file/d/0B2C16041iMhgbGpWY1RnNnpJZUU/view?usp=drivesdk

This track uses only Genesis FM and PSG. NO sampling.

While it's impressive, the frame rate is lower that the already low frame rate of Star Fox and there is less objects on screen. It may end up too gimmicky to make a good game. It certainly can't be a easy task to make a good 3D game on the Genesis without a extra chip, as if it would have been easy Sega would have put more 3D in their games to impress players.

Granted it would not have been easy or quite as polished as SNES. Though with the Sega CD architecture combined, it would have been even more feasible.

Case in point, Sega Genesis is fully capable of 3D polygons and action. And there were games that would exploit this from time to time. Though not often.

The 68000 is a power house compared to SNES CPU. But SNES has a good GPU and APU to make up for what the CPU lacks.


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22 Jul 2016, 1:21 pm

mr_bigmouth_502 wrote:
I'll admit, I like the version of the song in the video better. That one just blows me away with how awesome it is. But your version is a commendable effort too, especially since you didn't use any samples. ^^

But one thing I've noticed is that some of the better Genesis music out there tends to use the PSG in tandem with FM. I'm not a big fan of the PSG sound on its own, like on the Master System, but it works well alongside FM synthesis since it's hard to do square waves in FM.


Number one, PSG music for SMS is nice, if you compose well. Judge for yourself:

https://soundcloud.com/marcb0t/tarzan-boy-sms-version

But yes, it's really a special sound when PSG is used in conjuction with FM. I try to do this in my Genesis music, sometimes as harmony, and sometimes to thicken up FM instruments:

https://soundcloud.com/marcb0t/lunar-light-zone-past-v1

And in this next track, on one of the parts, you'll hear a square tone coming out of the left channel only.

https://soundcloud.com/marcb0t/central-command-v-0-1b

That is an FM square wave. They're not too difficult to make, actually. The resolution of the waveform is audibly higher, though.

And you'll hear good examples of PSG being used in unison with an FM lead on one part toward the end.


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