This a modified version of Merit's MacPPP Link Access Protocol module for MacTCP that supports DTE rates of 115Kbps and 230Kbps on 660AVs, 840AV and PowerMacs. There are no other changes from Merit's 2.0.1 release but I thought the support for higher rates justified a bump of the minor version number. I also wanted some way to differentiate this version from an official Merit release (this most definitely isn't) and my initials are SD so that's why they're there. I'm releasing this since there are lots of Internet providers adding V.34 dialups now that the spec has been finalized and I'm sure there are other folks like me that want to get the maximum possible speed out of our nice expensive new modems.
Is a 115K or 230K DTE rate really going to be faster than 57.6K?
It depends on the data being transferred. The V.42bis data compression standard is theoretically capable of 4:1 compression. Therefore you'd want a 115Kbps DTE rate to fill a 28.8Kbps V.34 link w/V.42bis compression. In the real world most data doesn't usually compress better than 2:1 so a DTE rate of 57.6K is usually sufficient. On the other hand I've seen better than 8000 bytes/sec using Fetch to ftp a highly compressible text file (400K of repeating 'abcdef') over a 24K V.34 link. Using the Electronic Frontier Foundation's "Big Dummy's Guide to the Internet" as a test file I've gotten in the neighborhood of 6200 bytes/sec. BTW, does anyone regularly get 28.8K connects? My normal connect rate with a USR Courier V.34 on each end of the line is 24K with occasional 26.4K and very rarely 28.8K.
If you have a Hayes Optima 288, it supports a DTE rate of 230Kbps to feed their modified version of the V.42bis compression routine that's theoretically capable of 8:1 compression (as opposed to normal V.42bis' 4:1 max). Unfortunately I don't have one so I can't say what sort of throughput my test files would have at the 230K DTE rate.
Caveats
The changes to support the higher DTE rates make use of an undocumented and unsupported serial driver call as well as some direct manipulation of the Serial Controller Chip. This has been working for a few months on my 660AV and PM6100 but there are no guarantees.
What do I need to use it?
You need a Mac that supports serial DMA (i.e. a 660AV, 840AV or any PowerMac) and a true V.FC or V.34 modem attached to the built-in Modem or Printer port. The increased interrupt load for the higher rates is too much for non-serial DMA Macs so I'd strongly recommend against using it on one although I don't currently check the Mac type. If you insist on trying it on a IIfx or Quadra 900/950 you must make sure that you have set the serial ports to 'compatible' mode using the Serial Switch Control Panel. If you don't, you'll crash your Mac when you try to connect. Since I already said you shouldn't be using this software on one of these machines I don't consider this a bug so consider yourself warned.
Of course if your dialup PPP provider isn't using V.FC or V.34 modems with a 115K or 230K DTE rate on their end you won't see any difference. That part I can't help you with. :-)
Does it work with a GeoPort Telecom Adapter?
No. The GeoPort Telecom Adapter pod isn't really a modem. It's just the hardware required to connect your Mac to the phone lines. The rest of the modem functions are implemented inside your Mac. Apple may implement a V.34 version of the Express Modem software but I wouldn't hold my breath waiting for it. I wouldn't recommend it on the PowerMac either as the current V.32bis implementation of the software seems to be good for approximately a 30% slowdown on my 6100AV.
How do I use it?
If you aren't sure how to install MacPPP, see the accompanying 'Installing MacPPP' document. Once you have installed MacPPP 2.1SD, open the Config PPP Control Panel and hit the Config... button. Select 115K or 230K from the Port Speed popup menu. That's it. You should now be talking to your modem at a rate that supports the maximum possible throughput. If you selected a port other than the Modem or Printer ports you'll get an error Alert when trying to connect stating that the higher rates aren't supported for other ports and the rate will be changed to 57.6K.
Copyrights & Credits
MacPPP 2.1SD is based on MacPPP 2.0.1 which is Copyright ⌐1992-1993 Merit Network, Inc. and The Regents of the University of Michigan.
The changes from MacPPP 2.0.1 to 2.1SD are Copyright ⌐1994 by Steve Dagley. As is the case with Merit's statement regarding MacPPP 2.0.1, I make no guarantee about the performance or reliability of this software. Any risk in it's use is your own. Not for profit distribution is allowed/encouraged. This Read Me document must accompany any distribution. If you want to include this version in some sort of software collection (i.e. CD) all I want in exchange is a copy of the collection.
Thanks to Bill Coleman of Hayes for reminding me to think async instead of sync when programming the SCC for the higher rates. I've been doing code for 13-bit sync serial data for so long I forgot what async was. :-)
Thanks to Larry J. Blunk and the rest of the MacPPP programmers for making the source code to 2.0.1 available.
Version History
2.1SD - 12/11/94
First public release.
As always, revised this Read Me.
2.1SDb3 - 12/10/94
Third semi-public beta.
Due to popular demand (from Lyman Green) I have now updated the Config PPP Control Panel to show the 115K and 230K rates in the Port Speed popup.
Revised this Read Me once again.
2.1SDb2 - 12/08/94
Second semi-public beta.
Oops - left in a modified version of the modem init code that occasionally caused timeouts when trying to establish communications with the modem.
Cleaned up and expanded this Read Me.
2.1SDb1 - 12/06/94
First semi-public beta
Cleaned up the code somewhat and actually check for a suitable serial driver before making the calls.
2.1SDa3 - July 1994
Never publicly released.
Made sure selected port was modem or printer.
2.1SDa1 - July 1994
Never publicly released.
First build.
Known Problems
Apparently the software for the Axion serial port switching device makes the test for the internal serial ports fail and revert back to a DTE rate of 57.6K. I don't have one of these critters so it's kinda hard to figure out a workaround other than turning off their software.
