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Would it be worth sacrificing my card for decapping?


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It would be nice to know more about the internal state machine that handles PCM playback, as I've noticed time irregularities(and minor sound distortion) in the audio output related to the block/period size.

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I would be happy to help but i don't have a working system that can use ISA cards anymore.

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There's nothing you can really get at from an ISA slot anyway, the Intel MCU in the upper left would have to be decapped.

MESS emulates the ATI Stereo FX clone where the 8048 program was a separate ROM, but I don't know how well it reproduces the quirks Mednafen is talking about.

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Here are some notes I made a while back regarding the glitch if anyone wants to check(notes are valid for auto-init high-speed DMA mode):

/*
Playback rate with various raw block sizes:
0 = 2/3
1 = 4/5
2 = 0.8577 with SEVERE distortion.
3 = 0.8894
255 = 0.9986 with some distortion
*/
/*
TODO? (still need to test stuff with raw block sizes >= 256)
(NOTE: Pseudocode below requires fractional/floating point precision)
actual_rate = 1000000 / (256 - raw_time_constant + 11 / (raw_block_size + 1))
*/

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The PCM playback is done entirely by the program running on the Intel microcontroller so reading it out via decap and then disassembling it would provide the ultimate reference.

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digshadow said that if you send the card he's fine with decapping the mcu.

LN


"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"
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Originally Posted By Lord Nightmare
digshadow said that if you send the card he's fine with decapping the mcu.

LN


Sounds good if you want to PM me the shipping address.

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Made a better scan of card front and back in case its needed later on.

http://imgur.com/Cvb3IOR
http://imgur.com/XimHTfK

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I have a Sound Blaster Live 5.1 and a (non-functional) Sound Blaster X-Fi laying around if anyone wants them for decapping or emulation. Just say the word and I'll ship them wherever...

ETA: The X-Fi is recognized by Windows and drivers can be installed but it only outputs static so it's not completely dead.

Last edited by Waremonger; 07/02/14 03:28 AM.
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