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MAME and EDD files [message #339993] Wed, 22 March 2017 09:58 Go to next message
zellyn is currently offline  zellyn
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Registered: April 2013
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Hi folks,

Paul Hagstrom's EDD Project page (http://yesterbits.com/topics/edd-image-project/) mentions that MAME is close-but-no-cigar to being able to read EDD files.

I was wondering what the current state of things there is. Are folks working on bringing it up to OpenEmulator compatibility? What still needs to be done?

qkumba? Nick Westgate? Yesterbits? :-)

Thanks,

Zellyn
Re: MAME and EDD files [message #340007 is a reply to message #339993] Wed, 22 March 2017 12:10 Go to previous messageGo to next message
Anonymous
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Originally posted by: paulhagstrom

On Wednesday, March 22, 2017 at 9:58:05 AM UTC-4, Zellyn wrote:
> Paul Hagstrom's EDD Project page (http://yesterbits.com/topics/edd-image-project/) mentions that MAME is close-but-no-cigar to being able to read EDD files.
>
> I was wondering what the current state of things there is. Are folks working on bringing it up to OpenEmulator compatibility? What still needs to be done?
>
> qkumba? Nick Westgate? Yesterbits? :-)

I haven't been watching MESS/MAME development very closely recently, so my information might well be out of date. I believe at least that last time I looked at it, the approach to EDD files was essentially to grab, per track, an approximate tracks'-worth of bits out of the 2.5 tracks of bits stored in the file. In my experience the reads were noisy enough that this didn't wind up picking the "right" bits very consistently. It's quick to implement but I found that it wasn't as successful as Open Emulator was (where a track can happily have 2.5x as many bits as it physically should have been able to). MAME/MESS references bits by angle, so it is only in principle possible to have one track of bits, no oversampling. OE just reads until it runs off the ends of the bits and cycles back to the beginning, and that, just anecdotally, winds up much better able to boot disks.
Re: MAME and EDD files [message #340008 is a reply to message #340007] Wed, 22 March 2017 12:22 Go to previous messageGo to next message
Anonymous
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Originally posted by: paulhagstrom

On Wednesday, March 22, 2017 at 12:10:04 PM UTC-4, paulhagstrom wrote:
> [...] OE just reads until it runs off the ends of the bits and cycles back to the beginning, and that, just anecdotally, winds up much better able to boot disks.

Actually, one other thing that might be helping Open Emulator succeed (particularly with protections that are looking for this) is that it does explicitly emulate the "spurious bits" of the read amplifier, so after the second 0 bit it starts randomly returning 1s sometimes.

https://github.com/OpenEmulatorProject/libemulation/blob/dev elop/src/libemulation/Implementation/Apple/AppleDiskDrive525 .cpp#L378
Re: MAME and EDD files [message #340009 is a reply to message #340007] Wed, 22 March 2017 12:27 Go to previous message
qkumba is currently offline  qkumba
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Registered: March 2013
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That is an accurate description of what was and still is.

There are plans to fix it. Big plans. Plans that make other plans look really small. Really huge plans. And important? Woowee. You don't get any more important than those plans.

Unfortunately, the priority doesn't match the ambition because we have so many other things that we want to do in MAME first.
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