Anyone have CDX/Multimega internal pics?

[blackevilweredragon]

Then how did F-22 use the Z80, along with the 68K, to run the game logic?

What are you talking about?

I've read that F-22 needed such an extra boost in power to pull off the choppy polygons, they used the Z80 too, to handle it with the 68k...

[RobIvy64]

Then how did F-22 use the Z80, along with the 68K, to run the game logic?

What are you talking about?

I've read that F-22 needed such an extra boost in power to pull off the choppy polygons, they used the Z80 too, to handle it with the 68k...

That would be incorrect. How would the sound function if the Z80 is busy helping out with the polygons? This is something for another thread.

Stick a fork in this one, It's done.

[blackevilweredragon]

i don't know...  im probably incorrect on it, because F-22 interceptor isn't well documented anyway...

don't forget though, the 68k can do sound functions too (in the genny)

[kendrick]

Okay, everybody back to their corner. This is about as productive as arguing about whether or not the Jaguar is really a 64-bit system.

The main function of the Saturn's 68000 is a sound chip, this is evident in the way that emulators and ported games are coded. But a clever developer could also use direct hardware access to make any chip do anything he wanted. You could make an SH-2 chip run as a flip-flop if you thought it would be useful. You guys are arguing about the definition of what makes a whole system overclocked, and since there's no standard there's nothing to argue about. Seller be honest, buyer beware is the only rule that applies here.

SSF, as long as you're properly representing and letting everybody know the extent of the modification, your work there's no issue. Rob, as long as you properly understand SSF's modification and don't want to partake, there's no need to press the argument. Don't make me pull out the moderator's strap-on device, please. :)

-KKC

[NFG]

I've re-opened the topic, but I'd like to echo kendrick's warnings about civility.  This thread has veered dangerously close to the asshole line, and I'd prefer that - if you can't keep it on-topic - you at least keep it friendly.  =)

was: Round Two: FIGHT!  

[RobIvy64]

He said he's overclocked the CDX. Wonder what the results were.  :huh:  

[Epicenter]

Argh. More cookie issues.

The Z80 in the MD/Genesis can be used for audio or as a general-purpose processor. The YM2612/PSG are both accessible from the Z80's address space, so the Z80 can control the audio subsystem. But all the 68K is doing to instruct it is writing it standard operations to perform, so you could just as easily run game logic code, as was suggested, on the Z80 and pass the results to the 68000. However, this means the 68000 must personally send the relevant instructions to the YM2612 synth and PSG for audio to be generated. Or the GLU chip can be flipped into 'SMS compatibility mode' by changing the voltage state of a cartridge slot pin to use the Z80 as the master processor (the VDP and PSG in the MD/Genesis are fully SMS compatible.)

Much the same case with the Saturn. The 68000 included is primarily utilized for audio, however, it could be used for running general-purpose code as well. Sadly the schematics I have access to do not include the 68000 so I am unable to analyze exactly how it is wired to the rest of the audio subsystem. I doubt it is directly connected and simply writes to it via the bus arbitration logic, so any of the system's processors could be made to push audio instructions.

That said, nearly all Saturn games perform game logic processing and (where relevant) 3D transformation calculations on the Master and Slave SH-2 processors. A comparatively minimal workload is put on the 68000, so overclocking this processor will have an extremely minor, or nonexistant, impact on game performance. What makes a system 'overclocked' is debatable, but I would argue against selling a machine without its primary CPU or Video logic performing more optimally than it did before the modification was performed, (which an overclocked 68000 won't produce) would be deceptive, since the user will experience no performance benefits for their money.

Compared to, say, a system wherein the CPUs run 30% faster and game slowdown is reduced, it'd be hard to justify spending an extra cent for an overclocked 68000 in the Saturn. That'd be like paying more for a high-end gaming PC wherein only the sound card's processor is overclocked, and overall game framerates remain wholly unchanged.

Edit: By the way, overclocking the 68000 shouldn't speed up the music tempo unless it was also recieving instructions at a rate that permitted it and there was no secondary means of synchronization. Overclocking the Z80 in the MD/Genesis causes audio to speed up, seemingly because the 68000 is writing audio instructions to the Z80 as fast as it can receive them, and there is no means of timing them at the 68K's end since the Z80's speed is (ordinarily) fixed at ~3.58 MHz so its # of operations completed in a certain amount of time is uniform.

[blackevilweredragon]

All this SH2 talk is making me want to overclock my 32X, if that's even possible...  It would be nice if DOOM played a little, uh, smoother...

[Segasonicfan]

He said he's overclocked the CDX. Wonder what the results were.

10Mhz: everything boots and seems to run fine
12Mhz: everything boots but not everything runs (Sonic 2 multiplayer)
14Mhz: boots with major glitching

I've only done testing with Sonic 2 so far but I'm confident the 10 and 12Mhz OCs are good enough for a permanent mod.

-Segasonicfan

[RobIvy64]

He said he's overclocked the CDX. Wonder what the results were.

10Mhz: everything boots and seems to run fine
12Mhz: everything boots but not everything runs (Sonic 2 multiplayer)
14Mhz: boots with major glitching

I've only done testing with Sonic 2 so far but I'm confident the 10 and 12Mhz OCs are good enough for a permanent mod.

-Segasonicfan

And how does it work with the Sega CD?

[Epicenter]

In my experience most MDs, with the exception of those with Signetics processors, will boot and run stable anywhere from the default 7.67 up to 10 MHz without incident, and USUALLY 11-12 MHz. If I had to pick one frequency to set a machine at and never change it, for max compatibility vs. speed I'd pick 10.5 MHz.

[Segasonicfan]

And how does it work with the Sega CD?

I thought somebody on the forums said that the Sega CD can't be overclocked?  Since I read this somewhere I haven't attempted to do it.  I would prefer to not mess with the surface mount 68k unless I know the Sega CD can be overclocked...

-Segasonicfan

[RobIvy64]

And how does it work with the Sega CD?

I thought somebody on the forums said that the Sega CD can't be overclocked?  Since I read this somewhere I haven't attempted to do it.  I would prefer to not mess with the surface mount 68k unless I know the Sega CD can be overclocked...

-Segasonicfan

Oh no the sega CD won't run overclocked, however, i'm curious to see how Sega CD games run with the Genesis' CPU overclocked (since most Sega CD games use the master 68K).