2007-07-31 06:42 am (UTC)

It's already doing a byte-for-byte copy. The point here is that there's an extra I/O port access (which can be excruciatingly slow) after every single byte as a slowdown, which is unnecessary. I'm not just saying it's unnecessary because we're all naïve about hardware, but because it didn't exist in 6.9. By a quirk of the modular tree, versions 7.0 and later use the I/O port access, whereas versions 6.9 and earlier just swap BL and BH about ten times as a delay, which, I'm sure you know, will generate no delay whatsoever on any machine made after 1995.