Re: 3860 bytes per second on a 38400 bps line

From: David Wood (
Date: 2003-06-05 17:02:34

On rs232 it takes at least two bits to frame a byte:

1 start
8 data
1 stop

Thus its easy to calculate throughput on a saturated unblocked line: remove
a zero.


On Thu, 5 Jun 2003, Marko [iso-8859-1] Mäkelä wrote:

> I released a new version of c2nload, the fastloader for my RS-232 based tape
> drive emulator (
> This version has two new features: the ability to disable automatic start-up
> of the program, and the ability to load data to the RAM area $d000-$dfff on
> the C64 and C128.  It also fixes a bug on the 264 series: there, tape file
> names are 17 characters long, not 16.
> I measured the transfer speed on the C64, C128, Vic-20 and plus/4 (not on
> the PET, as my 8032 is a bit difficult to access).  Loading a 3-byte program
> file takes almost 6 seconds.  Loading a file from $400 to $ffff on the
> Commodore 64 takes 22.618 seconds real time (and virtually no user or system
> time), measured with two different files copied from /dev/random.  The
> transfer of the last 64511 bytes takes 16.709 seconds, which yields a transfer
> rate of 3860.8 bytes per second.  I would have expected that a 38,400 bps line
> with 8 data bits and one stop bit would only yield 3840 bytes per second.
> 	Marko
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