The Turbo ASB Card

As the speed of today's fastest modems leaps from 14,400 bps to 28,800 bps and beyond, the hardware inside our computers that handle this faster information takes on increasing importance. When serial interface cards like the Apple Super Serial Card and Applied Engineering's Serial Pro were introduced, the idea of telecommunication at or above their 19,200 bps upper limits was merely a fantasy.

When 14.4k bps modems began to filter into the consumer market within the last year or so, many serial card owners began to feel the approaching port rate ceiling and, when it became apparent that the new 28.8k bps modems would soon be following, a so lution was needed to enable the serial cards to take full advantage of the new modem's capabilities.

In 1993, Lightning Systems opened its doors and began selling telecommunication enhancements for the Apple //. Their featured product, the Turbo ASB, is an add on board to the Super Serial Card or AE Serial Pro which removes the 19.2k bps limits and e xtends it to a whopping 230,400 bps, faster than any current Apple // should need to go. The Turbo ASB is an external baud (bps) rate generator for the 6551 chip that most serial cards for the Apple // have on them. It supports all of the standard bps r ates that the original serial interface comes with and adds 38.4k, 57.6k, 115.2k, and 230.4k bps.

The Turbo ASB is a small (about two inches by two inches) board that takes the place of the 6551 chip on the serial card. It effectively blocks the slot next to the serial card, but Lightning Systems is developing a cabled version that will allow the board to be used without blocking a slot so that 'power users' with fully loaded CPU's can take full advantage of all of their slots. The board also contains an updated version of the 6551 chip which corrects a problem in some of the older serial cards that caused characters to be lost. In many typical high speed configurations where Hardware Handshaking cables are used, the computer will send and receive data faster than the modem can receive and transmit. The computer and the modem handle the differe nce in speeds by allowing the modem to switch the Clear to Send (CTS) line when it's buffer fills, instructing the computer to stop transmitting data. The original 6551 chips would stop sending data immediately and, if the computer was transmitting a cha racter when this CTS signal was received, the lost character would result in an error. The new 6551 chip allows the computer to complete any characters it is the middle of sending and avoids transmission errors.

The Turbo ASB has had some very impressive performance results. When tested on an 8 Mhz Zipped //e and a direct serial link through a US Robotics v.32 modem, the transfer of a 256k file of ascii text resulted in an 8000 cps transfer rate --about 480k of data per minute! Of course, in real world file transfers of compressed data, the actual kilobytes per minute would be less, but the numbers still reflect a staggering amount of information transferred when compared to a top end speed of 19.2 bps of a standard serial card.

The Turbo ASB currently supports ProTERM v3.1, ANSIterm v2.12, and Spectrum v1.0 and higher. The support for these software packages is configured by setting the three DIP switches on the board. The possible speeds/switch combinations are shown in th e table below:

Standard|	Turbo ASB Rates	Rates	

| S1-1 ON S1-2 ON S1-3 ON
50 | 100 50 25 75 | 150 75 38 109.9 | 220 110 55 134.58 | 269 135 68 150 | 300 150 75 300 | 600 300 150 600 | 1,200 600 300 1200 | 2,400 1,200 600 1800 | 3,600 1,800 900 2400 | 4,800 2,400 1,200 3600 | 7,200 3,600 1,800 4800 | 9,600 4,800 2,400 7200 | 14,400 7,200 3,600 9600 | 19,200 9,600 4,800 19200 | 38,400 19,200 9,600 Ext./16 | 230,400 115,200 57,600

If you need to use the baud (bps) rates provided by your original Serial Interface Card, set the switches on the Turbo ASB as follows:

If you use ProTERM 3.1, you need to use a 'new' version of the PT3.CODE0 file available for download from the INTREC BBS. To achieve the full 230.4k bps rate, there is also a modification to the PT3.Global file included with the ASB's documentation. The proper configuring of the DIP switches for the supported software products is included with the ASB's documentation.

ANSIterm v2.12 directly supports the Turbo ASB in its set up menu and proper DIP switch configuration is included in the documentation. Spectrum user's should note that the maximum suggested 'port' rate setting (for v 1.0) is 38.4k bps. Speeds above this are extremely high for any Apple II computer and because of the GS/OS nature of Spectrum, under some conditions the software may not be able to keep up with the data at 230.4k bps. This has not been tested with the new (v2.0) version of Spectrum a nd it is possible that the potential problem may have already gone away.

The Turbo ASB cards are $27.00 each.
Shipping and handling is as follows:

Within the U.S., $3.00 per order.
Canada and Mexico, $5.00 per order.
Everywhere else, $10.00 per order.

Include an E-Mail address if you have one. Monies need to be sent in US funds.

Mailing Address (United States)

Lightning Systems
P.O. Box 4
Mukwonago, WI 53149

Bulletin Board (BBS to call with modem)
Lightning Systems
(414) 363-4282 200megs 21.6k USR Dual Standard

Ron Higgins of Lightning Systems is the developer of the Turbo ASB card. He currently works full-time as an Associate Engineer for a telecommunications manufacturer while continuing his study for a degree in Computer Science. He can be Emailed at

This article was reprinted with the kind permission of Auri Rahimzadeh, editor/publisher of PowerGS Diskazine. It appeared in issue number 5.

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