Found the reason for the Windows slowness. The .asc file was on the flash drive I am using to move the projects between computers. The run leaves a 130MB .raw file in the directory where the .asc file is. I can see the drive becoming 100% busy in the Task Manager during the run.
Once I copied the file to the local SSD and ran from it, it is way faster, about 16s. Haven't tried this on Linux laptops yet, but it is obviously an issue of Windows file access being very slow to the USB flash drive compared to Linux. The stick is USB 3.0 Lexar 64GB, fairly old. I am happy with its speed otherwise. Big file writes are 20-30MB/s, reads 80-100MB/s under both systems.
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Mike
