Developer help: F-Zero GX

[buddh4sack]

Are there any other developers out there who've taken a look at why F-Zero GX hangs at the login screen? I've just downloaded and compiled Dolphin recently, enabled the "debug ISO bootup" option, and am trying to take a look.

Any help, pointers or techniques would be much appreciated; I'm a professional software developer with experience in assembly (sun sparc and x86) as well as C/C++ (I say this only in the hopes of convincing knowledgeable persons that they won't be wasting their time in helping me out. )

Thanks!

[John Peterson]

Where's the "debug ISO bootup" option? Do you mean starting Dolphin with the -d option? Is it an option in the code that can be enabled? In addition to the normal LOG(BOOT, "...") function?

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Last edited by John Peterson; August 16th, 2008 at 07:06.

[EleQusion]

Originally Posted by buddh4sack

Are there any other developers out there who've taken a look at why F-Zero GX hangs at the login screen?

It's because the TLB isn't emulated.

Issue 103 - dolphin-emu - Google Code
Issue 123 - dolphin-emu - Google Code (dublicate, some more information)

[buddh4sack]

Originally Posted by John Peterson

Where's the "debug ISO bootup" option? Do you mean starting Dolphin with the -d option? Is it an option in the code that can be enabled? In addition to the normal LOG(BOOT, "...") function?

No, there doesn't seem to be a command line switch for it. I only found it because the debugger was behaving very strangely when I tried out F-Zero GX; when I tried to step, the PC was jumping all over the place. It turns out that the debugger doesn't go into "step" mode until after the initial iso boot. I changed the following line of code to make it start debugging right away:

Boot.cpp: line 442

bool CBoot::BootUp(const SCoreStartupParameter& _StartupPara)
{
    const bool bDebugIsoBootup = true;

And thank you, EleQusion, for cluing me in about the TLB. Is there anyone currently working on this effort? Or any specs I could try to read?

(My problem might be occurring earlier than this; my copy of F-Zero GX isn't producing that message... it just loops around the first Sega/Nintendo startup image again and again.

[EleQusion]

Originally Posted by buddh4sack

And thank you, EleQusion, for cluing me in about the TLB. Is there anyone currently working on this effort? Or any specs I could try to read?

As far as I know, nobody is working on TLB. The only documentation is the famous 'Yet another Gamecube Documentation' located Yet another Gamecube Documentation

[daco]

Originally Posted by EleQusion

As far as I know, nobody is working on TLB. The only documentation is the famous 'Yet another Gamecube Documentation' located Yet another Gamecube Documentation

indeed nobody is working on TLB and its last on their todo list.
afaik implanting TLB will decrease speed drasticly

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[buddh4sack]

Originally Posted by EleQusion

As far as I know, nobody is working on TLB. The only documentation is the famous 'Yet another Gamecube Documentation' located Yet another Gamecube Documentation

Awesome; thanks, this is precisely the sort of info I was hoping you experienced guys could point me to. Even if implementing a realtime TLB is not feasible at this point in time, I'm still going to press ahead a bit with it... My interest is probably different than most people here, as I specifically want to analyze and understand the awesome 3-D engine that exists in this particular game.

[memberTwo]

The only documentation is the famous 'Yet another Gamecube Documentation' located Yet another Gamecube Documentation

There's better specs somewhere.
Google for a Gekko's specific paired instruction like "ps_rsqrte" and you should find a heavy pdf.
It seams to be the good one, so far... (I've just started to read it)

[ector]

The TLB/MMU is similar to that of other PowerPC processors so just read any ppc manual that details the TLB. Or steal code from PearPC.

In any case, it's gonna be SLOW.

[Hemi3]

Originally Posted by ector

The TLB/MMU is similar to that of other PowerPC processors so just read any ppc manual that details the TLB. Or steal code from PearPC.

In any case, it's gonna be SLOW.

Wouldn't it just be slow on games that use these features and the ones that do not use TLB at all would not be affected? At least the games that use it would run slow instead of not at all.

[John Peterson]

Originally Posted by ector

In any case, it's gonna be SLOW.

Why will it be slow if it works as usual on the GameCube? Can't you recompile these instructions as you do with the other instructions? Could you elaborate?

[buddh4sack]

Originally Posted by John Peterson

Why will it be slow if it works as usual on the GameCube? Can't you recompile these instructions as you do with the other instructions? Could you elaborate?

If I learn enough, I'll post everything I know.

I'm curious about another issue; in the F-Zero GX iso, there are a lot of ".lz" files... I'm guessing this is standard LZ77 compression, but I'm not having any luck decompressing them. Any ideas? Thanks!

[ector]

Originally Posted by John Peterson

Why will it be slow if it works as usual on the GameCube? Can't you recompile these instructions as you do with the other instructions? Could you elaborate?

We have to make it cause interrupts on wrong memory accesses. This means that we can't compile stuff into blocks anymore, making it impossible to use the JIT.

[shuffle2]

Originally Posted by buddh4sack

If I learn enough, I'll post everything I know.

I'm curious about another issue; in the F-Zero GX iso, there are a lot of ".lz" files... I'm guessing this is standard LZ77 compression, but I'm not having any luck decompressing them. Any ideas? Thanks!

check their headers in a hex editor.


also, tlb is ugly and scary

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[mudlord]

Isn't F Zero GX by Nintendo?

If so, Yaz0 compression might be used (if I am not mistaken, if it really is a Nintendo EAD production).

[hcs]

F-Zero GX was developed by Sega, actually. Thus the predilection for ADX...

[NexXxus]

errm wasn't f-zero on an GD-R ?
ah no that was f-zero AX ...

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[buddh4sack]

Originally Posted by hcs

F-Zero GX was developed by Sega, actually. Thus the predilection for ADX...

Actually, it was co-developed by a Sega subsidiary (AV Entertainment) with Nintendo (it's still strange to think of those two cooperating on a project). Shigeru Miyamoto (of Mario fame) was the lead producer on the project.


I did look for a header in the .lz files; some of them are even nicely named *.arc.lz, so I know that they should decompress to something that has the arc magic number in them... but there seems to be no common header at all.

I'm still poking around all the files; since this is the first GameCube ISO I've tried to dissect, I'm not sure what's "standard" and what's not. From inspecting files in the &&SystemData data directory (AppLoader.ldr and Start.dol) I can see they used the Metrowerks Power PC kernel, and there are functions for reading ARC files in there. I'll need to understand the boot process a bit more; I'm busy checking out Core/Source/Boot/Boot.cpp right now.

[hcs]

I'd say "I stand corrected", but I'm going to cling to the fact that what I said wasn't technically wrong

[buddh4sack]

Originally Posted by hcs

I'd say "I stand corrected", but I'm going to cling to the fact that what I said wasn't technically wrong

Oh, I didn't mean to seem like I was nitpicking; I just find it fascinating that Sega and Nintendo, who were such intense rivals for all my early gaming years, actually teamed up on something.

And I see that the first thing called from the iso is at address 0x20 of the AppLoader.ldr file, so I've got a good place to start my analysis.

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Last edited by buddh4sack; August 20th, 2008 at 19:04.