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#1
Technical questions and looking for oddities
Posted on: 2/11 13:17
Newbie
Joined 2/11
2 Posts
TL;DR: Speedrunner looking for potential techniques

Hi all,
I'm currently maintaining two projects (in a different community) about potential techniques on different platforms that could be considered for speedrunning purposes.

I'm looking for two primary things edit: regarding Virtual Boy:
- answers to my 2 technical questions,
- any experiences of oddities on a real hardware.

1 - Sub frames input
- Is it possible for a game to poll the controller multiple time within a single frame (x02000010, 0x02000014, 0x02000028)?

2 - Cart swapping
- Does it have a "cart lock", a plastic piece preventing cart swapping while the console is powered on?

If you are interested in my current state of my projects, here are the links:
http://tasvideos.org/PlatformResources/Vboy.html
http://tasvideos.org/MESHUGGAH/ForbiddenTechniques.html

Thanks in advance :)
Edited by MESHUGGAH on 2019/2/11 13:35
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#2
Re: Technical questions and looking for oddities
Posted on: 2/11 14:26
VUE(xpert)
Joined 2012/12/4
418 Posts
CoderLong Time User (6 Years)
Quote:

MESHUGGAH wrote:
Is it possible for a game to poll the controller multiple time within a single frame (x02000010, 0x02000014, 0x02000028)?


Yes, the game pad component operates independently from the video component, so input can be processed multiple times per display frame. I don't know if any commercial games do this, though; honestly haven't checked. If I had to place a wager, though, I would guess that all commercial games process input once per frame.

Quote:

MESHUGGAH wrote:
Does it have a "cart lock", a plastic piece preventing cart swapping while the console is powered on?


There's nothing preventing the cartridge from being removed while powered on, but I don't know whether or not the hardware will issue a reset interrupt when inserted. Even if it doesn't, the open bus behavior (zeroes gives you MOV r0, r0, ones gives you OUT.W lp, -1[lp]) will send the current program position rocketing out of the solar system, making it impossible to reliably time the insertion correctly.
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#3
Re: Technical questions and looking for oddities
Posted on: 2/11 15:49
PVB Elite
Joined 2008/12/28
Slovenia
628 Posts
Highscore Top ScoreHighscore Top ScoreCoderContributor10+ Game RatingsLong Time User (10 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Hot-plugging cartridges has been discussed before:

https://www.planetvb.com/modules/newbb ... t_id=26057#forumpost26057
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#4
Re: Technical questions and looking for oddities
Posted on: 2/11 16:29
Newbie
Joined 2/11
2 Posts
1 - So subframe input polling is possible technically, thanks! Will check the released titles and see if I find multiple polling.

My first idea would be simply putting a breakpoint on reads to 0x02000028 and check Bit 1 (Read) Hardware Input in Progress how many times changes in a single frame.

2 - Good, so no plastic piece lock.

The linked thread mentions:
"insert a cart with battery backed SRAM while the system is on, the system resets."

Other note I see on VB Development Wiki:
"In commercial cartridges, /RESET (pin 7) is connected to the SRAM CS2 and MM1245 reset IC. This is done in order to protect the SRAM from spurious writes during power-failure and during startup when VCC is unreliable/unstable."

Does this affects other (released, commerical) cartridges too?
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