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CHD disc images have transfers that are 60-70% slower than non-compressed formats #252

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@Zaspath

USBODE 3.4.0 / Pi Zero 2W / 64-bit build

Tested ISO/CHDs, various, in this example Stone Keep as it has a large 320mb file called VOICES in the Data dir.
Available here: https://archive.org/download/20230723_20230723_0858

From a CHD compressed with '-c cdzs,cdfl' the transfer
Taken from: https://docs.mamedev.org/tools/chdman.html#compression-algorithms
(A blend of a good compression/decompression)

Bin/Cue stats
average transfer: 6.0mb/s / 53 seconds

CHD stats, compressed with a light algorithm cdzs & cdfl
average transfer: 2.1mb/s / 3 minutes 12 seconds

Transfers on a Windows 11 PC so that the destination system is not in question in terms of power/USB performance.
Compression/Decompression normally benefits greatly from an increased core count, perhaps there is a multi-threaded handler for this format that can be used that will reduce the performance hit?

Thanks.

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