Re: IIGS 115,200 Baud Serial Port - How?

[Hugh Hood <hughhood@earthlink.net>]

Fellas,

It turns out that the 115,200 baud IIGS built-in SCC port ProTERM 3.1
patches _were_ a success. When I connected another IIGS up to a host machine
that could actually support a 115,200 baud serial port, ProTERM 3.1 (patched
for 115,200 baud) shined.

Thanks go out to David Schmidt, David Wilson and David Empson, whose replies
forced me to look more closely at the Zilog 8530 SCC manual and try one more
time.

To obtain a rough benchmarch comparison, I did a Zmodem null-modem transfer
of an uncompressed 33.5K AppleWorks Spreadsheet file from ProTERM 3.1 on the
Apple IIGS to a Mac OS X machine running in the background the rz/sz Zmodem
Unix programs, controlled of course from the getty-enabled Apple IIGS serial
terminal. 

Here are the results of the error-free Zmodem transfer at (2) different
speeds:

                    File Size     Time        CPS
                    ------------------------------------
57,600 baud         34,211 bytes  7 seconds   4901 cps

115,200 baud        34,211 bytes  4 seconds   8577 cps


Obviously, the 115,200 baud (and even the 57,600 baud) CPS file transfer
rate is significantly higher than that obtained from a 9,600 or 19,200 baud
connection. In addition, normal terminal work is _very_ snappy at 115,200
baud compared to the lower baud rate connections.

Please keep in mind that these results were obtained with an 7/32 Zipped
IIGS connected via hardware handshaking cable to a PowerMac G4 with a PCI
slot serial card. Both the IIGS built-in serial ports and the PowerMac PCI
slot card serial ports were RS-422, and cabled accordingly.

I do suspect that a IIGS _without_ an accelerator might drop some characters
at this speed during a screen update, but that Zmodem transfers would not
suffer from that, since the screen is not updated during those processes.

I'm really amazed that ProTERM 3.1 can keep up with the screen updates at
115,200 baud, but it does. What a program!

Anyway, I'll prepare a short post describing how to make these patches to
ProTERM 3.1 with a block editor, such as ProSel's Block Warden. The main
patches are to PT3.CODE0. There are a few 'cosmetic' patches in PT3.CODE1 to
reflect the fact that the baud rate is 115,200 and _only_ 115,200. Since
this patched copy of ProTERM is a single baud pony, you would want to keep
it as a _separate_ program on your drive.

If Tony Diaz thinks it appropriate (and legal, and wanted), I'll just upload
the patched versions of these (2) files to his new home for the freeware
ProTERM. But, I'll wait to hear from him first.

Hugh Hood...
 








in article C586DF38.14DE%hughhood@earthlink.net, Hugh Hood at
hughhood@earthlink.net wrote on 1/4/09 9:48 PM:

> Concerning patching ProTERM 3.1 to achieve 115,200 baud from the IIGS serial
> port(s), I must mention that there's a _chance_ that my final patches will
> produce positive results.
>