It was 1985. Just 3 years before, Commodore had made telecommunications affordable, releasing the first modem on the market that retailed for $100. They weren’t just making it possible to live in the future, they were making it affordable. But the industry was passing them by. Commodore needed to catch up, and the 1670 modem 1200 was what they came up with.
Commodore modems: Slow and incompatible, but cheap
The knock on earlier Commodore modems was that they were slow, and not compliant with industry standards. A Commodore modem could interoperate with other modems, but from a programming standpoint, they didn’t follow industry standards. They weren’t even compatible with each other, so terminal software that worked with one Commodore modem may not necessarily work with another.
To some extent, this was understandable. Commodore was trying to hit aggressive price points, and that meant licensing technology from the lowest bidder. And somebody who was complying with the Hayes standard didn’t need to be the lowest bidder. They just needed to be a little bit cheaper than Hayes.
How the Commodore 1670 modem was a winner
With the 1670, Commodore introduced a modem that operated at 1200 bits per second rather than 300 bits per second. It was also Hayes compatible. The price was reasonable at $200, and Commodore aggressively cut the price over time. By 1988, mail order houses were selling it for $60. Cheaper modems at the same speed existed like the Volksmodem 6480, but they didn’t have that degree of compatibility. This time, Commodore avoided that siren song and they produced a winner. Mostly.
Like earlier models, the 1670 plugged into the user port on the left hand side of the machine. This unusual port had both serial and parallel signals on it. The serial signals were not quite RS-232 compliant, which saved money because it eliminated two chips inside the computer and two chips inside the modem.
It initially sold for $200, which was a good price for a modem of that speed in the mid 1980s, and they didn’t compromise much on quality to get to that price point either. The OEM for the internals was none other than US Robotics.
The two versions of the Commodore 1670 modem 1200
There were two versions of the 1670, and the easiest way to tell the difference between them is to look at the back. The early model had three dip switches in the back, and the later model had four.
By some accounts, that’s the only difference between the two. But that’s not quite the case. I remember being told that the early model was compatible with the Hayes command set, but the registers weren’t all in the same place. The most straightforward commands like the commands to dial the phone, hang up the phone, and reset the modem where all the same. But the command to set the register that controlled how quickly it dialed the phone wouldn’t necessarily be the same. Depending on how fancy your software decided to get, it wouldn’t necessarily work right if it was expecting a genuine Hayes modem.
The later version changed that, and it even said so on the box. A big sticker on the box proclaiming it was the new and improved version boasted of being 100% Hayes compatible.
And by all accounts, it was a really good modem. It was reliable, it interoperated well with other modems, and it generally did not feel like a compromise, at least until inexpensive modems that operated at $2,400 that’s per second arrived on the market.
But there was a catch.
My experience with the Commodore 1670
I own at least one 1670, and I say that because I may have ended up with a second one at some point. But I started out with just one, because even the cheapest modems available at the time were somewhat expensive. And when I got mine, it didn’t work. The local Commodore service center wouldn’t look at it since we didn’t buy it from them, so we had to ship it back to Commodore in Pennsylvania. And they sent us back a tested working unit.
Except that one didn’t work either.
Getting help from a familiar friend
Lucky for me, I still had my old, slow modem, so I could use it to ask for help. And my friend Sonny, the grumpy guy who didn’t like Maverick and preferred Fast Hack’em, volunteered to help. He said he had two of them. That was on brand for him. His accumulation of Commodore equipment was legendary in these parts.
He called me later that night and told me to flip the modem over and tell him how the switches were set. I don’t remember how they were set but he immediately said I think that’s your problem. And he told me that he used his with all four switches down. So I set the four switches all to the down position, then we hung up the phone and I tried to call his modem with mine. And it worked perfectly.
Sonny said that wasn’t the first time he’d helped someone with theirs. Then he told me to write down on the modem to keep all four switches down so I wouldn’t forget. I didn’t write it down, and 35 years later, I still remember. The human brain is a really weird thing.
Eventually I upgraded to a 2400 BPS modem made by a company called Aprotek, and I thought I passed my 1670 on to someone else. But I found one in a box of old parts a few years ago, so I don’t know if it is my original 1670, or if I picked up another one somewhere along the way. Either is possible.
But the switches on that modem are all in the down position.
Oh Commodore, don’t ever change
I really wonder how much extra labor Commodore ended up spending because they didn’t ship the modem in that configuration, and they didn’t clearly state the recommended switch settings in the manual either.
But that’s on brand for Commodore too. Commodore was good at getting the big things right, or at least right enough. It was usually the little things they must stop at, and they messed up enough of them that they ended up not being a viable business.
But they made it possible to get a glimpse of the future, and they made it more affordable than anyone else, at least for a few years in the 1980s. And even though I wasn’t able to fix this problem myself, I did learn a lot of computer troubleshooting skills messing around with those Commodores, and I’ve been able to make a career of it.
David Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.
Hayes-compatible. I used to remember a lot more than ATA and ATH.