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Date: Fri, 16 Jul 2021 06:56:39 -0700
From: Larry McVoy <lm@mcvoy.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
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Subject: Re: [TUHS] 386BSD released
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On Fri, Jul 16, 2021 at 09:00:58AM -0400, Theodore Y. Ts'o wrote:
> The trick that I used was two have two "flip buffers" which were
> dedicated for each serial port.  One buffer would be filled by the
> interrupt handler, while the other would be buffer would be processed
> by the bottom half (read: software interrupt) handler.  When the
> bottom half handler had emptied one buffer, it would check to see if
> there were any characters in the other buffer, and if so, flip the two
> and process the characters in that buffer.  

I'm pretty sure SGI used a similar approach for networking packets.