[Coco] Serial Port file transfers

[Gene Heskett]

On Sunday 05 November 2006 23:03, Jim Hickle wrote:
>What sort of speeds should I be expecting from a 512k CoCo running
> NitrOS9, with an RS-232 pack connected to a Linux system's serial port? 
> I'm trying to transfer files and it's taking forever using floppies and
> the PCDos program.
>
>Using rz/sz on the coco I can set the ports no higher than 2400 bps.  I
> can bump it up to 4800 if transferring using Supercomm's Xmodem
> transfer.  Is this really the limit?   Maybe I should give up on serial
> transfers and use CD-ROM's?
>
Years ago now, I was using an amiga-2000-040 and Olaf Barthels term4.7 to 
measure that.  I was getting around 740 cps with the interfaces set for 
9600 on a nitros9-1.15 system, and about 430 cps with a stock 512k coco3.
This was using the auto-trigger of rz/sz-3.36 with supercom-2.3 for the 
term program on the coco3's.  Using the 7-wire protocol for flow control, 
not xon/xoff.

Using xmoden or ymodem, speeds in the 3000 or more cps range should be 
doable on a stock coco3 since they have a much simpler error checking 
method and send whole 128 byte blocks at a time whereas rz/sz is character 
at a time which makes its 24 bit crc checking a huge cpu hog.  But, rz/sz 
absolutely guarantees the data sent is good, the other two methods can let 
errors slip thru, and file sizes need trimmed as they record whole 128 
byte blocks even if the last byte of the file is the first byte of the 
last block, which makes the rx'd file 127 bytes too long.

If you can't set the ports any higher than 2400 baud, you have a flow 
control miss-match I think.  And because the acia chip has a bug, there 
was a minor re-wire of the rs-232 pack and a patch for sacia that fixed 
that bug if you wanted to use hardware flow control, commonly called 
7-wire.  That patch should be in the later sacia modules, its enabled by 
one of the xmode options and isn't documented anyplace but in that patch's 
readme that I know of.

Unforch, I don't recall the name of the patch, and I'm not sure that it 
survived the hack job when rtsi got hacked into several years ago.  I 
don't believe I have it myself now, as it was a casualty of a flaky hard 
drive & controller a decade+ back up the log.

>-jim hickle
>
>
>
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-- 
Cheers, Gene
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