Classic computing fanatic Cameron Kaiser has bought two items of classic know-how, a Commodore 64 and a Convergent WorkSlate, speaking collectively — over a “35-cent softmodem” that lets the 2 discuss over a wire as simply as a phone line.
“Of the various attention-grabbing posts from Usenet’s extra golden days, one among my favorites was John Iannetta’s ’35-cent modem,’ the place the [MOS Technology] SID chip gives one-way knowledge modulation to a receiving modem linked through the [Commodore] C64’s sound output,” Kaiser explains. “Whereas I bear in mind him posting it again in 1998, I by no means truly tried it on the time.”
No cellphone line? No downside! This intelligent “softmodem” turns a Commodore 64 right into a server for any modem-equipped gadget with only a easy cable. (📷: Cameron Kaiser)
Earlier than the times of high-speed connections, Wi-Fi, and Ethernet, the gold customary for computerized telecommunications was hooking your micro as much as a modem and having it dial as much as a distant modem and scream at it — modulating the digital knowledge from the pc into audio, sending it over the phone wires initially designed for voice visitors, and demodulating it again into knowledge on the different finish.
The Commodore 64 had no scarcity of {hardware} modems, however Iannetta’s design was totally different: utilizing the Sound Interface Machine (SID) chip within the Commodore 64 to exchange the majority of the modem’s {hardware}, requiring only some cents in elements to interface with an actual modem on the different finish of the road. Maybe surprisingly, it is a trick that works — and in Kaiser’s case, meant a brand new and low-cost option to get a conveyable Commodore SX-64 speaking to a Convergent WorkSlate.
“Formally the WorkSlate’s solely technique of telecommunications is its 300 baud inside modem,” Kaiser explains. “Whereas we have now a 9,600 bps manner of wiring up a Workslate to a contemporary laptop, it is all the time good to have a less complicated different, and I figured this could be an excellent problem to see if John’s outdated program might let my Commodore SX-64 discuss to my WorkSlate. Spoiler alert: it really works!”
The one {hardware} wanted is a customized cable, although Kaiser warns it ought to by no means be linked to an actual cellphone line. (📷: Cameron Kaiser)
Writing a modified model of Iannetta’s unique softmodem code, Kaiser was capable of get the Commodore 64 to behave as a modem speaking to the one constructed into the WorkSlate — even simulating a dial tone and activating the WorkSlate’s speaker cellphone perform. The addition of an XMODEM protocols permits the software program to switch information to and from the WorkSlate, too. “John was a great man with a intelligent programming type,” Kaiser says, “and it was good to see his code operating once more (and dealing, although that was a given). Plus, it is a nice use for a Commodore to assist your different programs, and a roadmap for doing one thing comparable on different machines with sufficiently succesful sound {hardware}.”
The highly-detailed mission write-up is out there on the Outdated Classic Computing Analysis weblog; the supply code is out there on GitHub, together with a precompiled binary, underneath a public area license; directions for wiring an acceptable cable are included. “By no means join this cable to a wall jack,” Kaiser notes. “You would ship 48V via your machine.”
