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gbdev research

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26 Jan 2022
@_discord_382273000554364949:t2bot.ionitro2k01#5984 This is while the payload is executing form HRAM which presumably is not mapped in/out by the switch. 13:30:19
@_discord_382273000554364949:t2bot.ionitro2k01#5984 I wonder if the GB core is actually powered down and is running on sheer willpower leakage current from other parts of the circuit. 13:32:34
@_discord_382273000554364949:t2bot.ionitro2k01#5984 And I need to figure out some way of physically protecting my GB micro board. I feel like I'm going to break it any second. 13:33:42
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Hey, wait a minute. The whole GB SoC is running at half speed for some reason. 13:51:53
@_discord_382273000554364949:t2bot.ionitro2k01#5984 I wonder if I messed something up when writing to the boot ROM disable register which produced this effect. The GBC boot ROM is not running half speed. 13:54:12
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Ok, so simply loading and storing the value of 0x04000800 using a 16 bit access is not enough to halve the frame rate. 13:59:13
@_discord_382273000554364949:t2bot.ionitro2k01#5984 * Ok, so simply loading and storing the value of 0x04000800 using a 16 bit access is not enough to halve the frequency. 13:59:35
@_discord_364858838689513483:t2bot.ioTRJB like, even the sound is half speed? 14:26:10
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Yes! 14:41:28
@_discord_317029794598486018:t2bot.ioCasualPokePlayer#8731 what the fuck 15:38:21
@_discord_317029794598486018:t2bot.ioCasualPokePlayer#8731 secret half speed mode :o 15:38:33
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Maybe it's somehow clocked by glitch edges, somehow. That would fit how weirdly it behaves. 15:50:58
@_discord_382273000554364949:t2bot.ionitro2k01#5984 * Maybe it's somehow clocked by glitch pulses, somehow. That would fit how weirdly it behaves. 15:51:14
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Perhaps related to how I'm reading the register to change the bit, then writing it back. Might have set/cleared some of the mystery flags somehow. 15:54:25
@_discord_382273000554364949:t2bot.ionitro2k01#5984 I should also streamline my setup. Key to doing that is getting multiboot up and running, and also external power control so I can run multiple tests without touching anything physically. 15:57:44
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Unfortunately both SP and micro kind of suck for this. 15:58:08
@_discord_382273000554364949:t2bot.ionitro2k01#5984 SP can't run on just ext power from what I hear, and micro has a sift power button even if I hook up to the battery terminals. 15:59:03
@_discord_382273000554364949:t2bot.ionitro2k01#5984 Or does it? Not sure... 16:01:33
@_discord_415632131029729290:t2bot.iojvsTSX A1 pulse bass??????? 16:41:28
@_discord_415632131029729290:t2bot.iojvsTSX how 16:41:34
@_discord_415632131029729290:t2bot.iojvsTSX also is a good portion of the I/O locked after bootrom is done? 16:43:19
@_discord_415632131029729290:t2bot.iojvsTSX i see there's some plenty of unused registers even on $FF0X 16:44:03
@_discord_755055255426957412:t2bot.iozlago skitty changed their display name from zlago to zlago#4821.19:55:13
@_discord_755055255426957412:t2bot.iozlago skitty changed their display name from zlago#4821 to zlago skitty.19:55:18
@_discord_342897799295401996:t2bot.ioRetroFan90 joined the room.20:22:30
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@_discord_364858838689513483:t2bot.ioTRJBgbc_to_dmg_button_converter.png
Download gbc_to_dmg_button_converter.png
22:44:50
@_discord_364858838689513483:t2bot.ioTRJB if I'm correct and the GBC's button inputs are pulled up to VCC when that particular button group is chosen then this could work to change it so that the GBC SoC can work with the SGB's ICD2 chip 22:44:50
@_discord_364858838689513483:t2bot.ioTRJBgbc_to_dmg_button_converter.png
Download gbc_to_dmg_button_converter.png
23:07:05
@_discord_364858838689513483:t2bot.ioTRJB added a rudimentary timing diagram
in terms of one full button register "cycle", the buttons are pressed 66% of the time
however, if these "cycles" are spaced out and performed with a relatively fast clock speed, then that down time is most likely nullified by most GB software
23:07:05

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