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Author Topic: Doom SNES Multiplayer?  (Read 5923 times)

Kashim

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Doom SNES Multiplayer?
« on: March 30, 2014, 03:43:15 pm »
I had a nostalgic feeling this weekend so started to play Doom again on PC. Oh man... I love this game! I remember we always played 4 player deathmatches and co-ops all the time in primary school. Tried out SNES one some days ago: the musics are awesome, the graphics... meh not really. So came the question: SNES Doom has a multiplayer support? Turned out, unfortunatelly no. But on youtube I found this 2 videos, about that xband thing:
https://www.youtube.com/watch?v=-P3JGxBNUyM
https://www.youtube.com/watch?v=jONkFljFrck

Read about that snes modem and it was amazing at the time. After some "investigation" I noticed that it supported games without built-in multiplayer (like Doom) via downloading some sort of gamepatch which "soft moded" the game's rom.
So imo its possible to retrieve that xband gamepatch and somehow put it into the game by IPS patching or making an own IPS patch for that purpose, right?

FAST6191

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Re: Doom SNES Multiplayer?
« Reply #1 on: March 30, 2014, 08:34:12 pm »
Never even knew such a device existed before this.

First you and your friends would be considerably better served downloading a PC multiplayer version and getting USB to SNES adapters. If only because such a thing would handle latency and the like. For the other games then you are probably still better off finding something with Kaillera, or equivalent, support.

I would have guessed the xband was some kind of game genie equivalent (ROM patcher, possibly also some RAM patching options) and modem combo. This would tend to mean extra hardware that has to be emulated or replicated.

However the thought exercise is an interesting one and http://www.gamasutra.com/view/feature/131781/the_internet_sucks_or_what_i_.php will probably be as relevant as ever. The games picked seem to have already been multiplayer games at their heart, doom being the main exception though that is at best a minor distinction and possibly one that helps here (latency is more likely to be easier to deal with).

I do not know what level of onboard storage the xband had (I have not even looked to see if someone has pulled one apart at this point), the idea of online services going off would have been something of a new one so I doubt people made the effort to save it. If it was some kind of downloadable patch held in RAM then there is very little chance.

Being two player I imagine there would be something of a host-client model. In Doom's case I would have made a code to disable all enemies, unlock all doors and maybe regenerate pickups after a certain time. I would have then had the modem send pickup takings both ways, player locations both ways, player movement directions if movement alone would not have been enough to handle sprite directions, firing info and then had the local games manage ammo counts and whatever else (a firing offence for a modern game, here though there were rather limited resources for proper anti cheat). Frag counts was a nice touch, I wonder what was done for that.

The rest of the xband would then have been the in game menu (by the looks of things a level select, one that probably ran "if the same then choose that, otherwise random" if one of those videos was anything to go by) and the backend at xband HQ (I am guessing a modem bank and the charging/score keeping architecture). For this project I would probably start out replicating backend using some kind of null modem and sorting out the rest via other channels ("send me your IP address...."), or just remaking the patch* and using Kaillera.

*do the unlocks, regenerate pickups... have the second controller control an "enemy" modded to be the doom marine and then send data around for what I imagine is some kind of viewport rendering (plus ammo counts) on the client connection.

This is an awful lot of effort for Doom.

KingMike

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Re: Doom SNES Multiplayer?
« Reply #2 on: March 30, 2014, 09:47:19 pm »
So imo its possible to retrieve that xband gamepatch and somehow put it into the game by IPS patching or making an own IPS patch for that purpose, right?
That would require dumping the SRAM from an Xband with the patch pre-downloaded.
I remember reading there was one group that tried to collect as many Xband modems as they could to dump the patches for preservation (as well as emulation), but it was futile as all those they collected turned out to have dead batteries.

Also, I think Doom wouldn't have a patch as reportedly it was one of two games to have built-in support for Xband (the other was WeaponLord).
« Last Edit: March 30, 2014, 09:52:38 pm by KingMike »
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Kashim

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Re: Doom SNES Multiplayer?
« Reply #3 on: March 31, 2014, 02:25:39 am »
Quote
First you and your friends would be considerably better served downloading a PC multiplayer version and getting USB to SNES adapters

Yeah actually there are gzdoom and skulltag, so I could play Doom easily online with lot of mods etc. Just I am curious about that problem and it is a hacking site... so..  :)

Quote
This is an awful lot of effort for Doom.

Actually it was made with F-Zero VS. really well, maybe using/looking into client-host part of that emulator should help.

Quote
Also, I think Doom wouldn't have a patch as reportedly it was one of two games to have built-in support for Xband (the other was WeaponLord).

If that is the case, then the problem would be more simple: that multiplayer part is somewhere in the rom, maybe could trigger with a cheat or some sort of code.
« Last Edit: March 31, 2014, 02:31:49 am by Kashim »

KingMike

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Re: Doom SNES Multiplayer?
« Reply #4 on: March 31, 2014, 12:47:33 pm »
The other thing is that was clearly designed to run with two players on separate consoles (and most importantly, individual screens).

I suppose it could be done, but only a few people have ever made homebrew link cables (using the controller port).
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Gideon Zhi

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Re: Doom SNES Multiplayer?
« Reply #5 on: March 31, 2014, 01:07:10 pm »
It's certainly an interesting problem, and I must admit it's something I'd at least thought on briefly in the past. To answer one line of inquiry before it gets asked though, online multiplayer as it's currently implemented in ZSNES and SNES9X assume that the players are sharing a screen; even though they're running two different emulators on two different monitors, it's still the "same" screen (barring any desynchronization issues, anyway), so netplay's presence doesn't make things any easier.

Kashim

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Re: Doom SNES Multiplayer?
« Reply #6 on: March 31, 2014, 03:47:33 pm »
Just thought it's somehow managable if there were people who could make an F-Zero VS. emulator too