| eric.kuhnert-design.com | English | Deutsch | |
Published / Modified: 2024-09-18 / 2025-06-21
There suddenly was a Macintosh Performa 630CD on my desk. And after a fresh installation of System 7.5.3 files were due to be copied onto the machine. But how?
Although the Macintosh Performa 630 was the first Apple computer to ship with an IDE harddrive - instead of SCSI - Ethernet networking was only available as COMM-port upgrade card (which my specimen unfortunately did not have). However it featured the famous floppy SuperDrives (which handle 400K, 800K and 1.44M floppy diskettes) and the 630CD even came with a SCSI-based CD-ROM drive (which cannot read CD-R or CD-RWs). In addition to video-out (DB-15) and ADB two serial ports labelled Modem
and Printer
were present.
Sure, creating split archives were each part fits onto a 1.44M floppy diskette is one way to get files across. Stuffit presents itself, as it can be unpacked in the Macintosh quite easily. But such a process requires another older Mac or a virtual machine - both with a diskette drive - and would be pretty hands-on
. If in the 1990s one could connect to a local network thanks to LocalTalk or even the world wide web through a modem hooked up to one of these serial ports this interface should be good enough for the occasional file transfer today, right?
The idea was to pair up the Macintosh with another machine which has serial ports and can access network resources over Ethernet. A minimalistic bridge system, so to speak.
Apple has often reinvented the wheel. Although earlier Apple computers offered DB9-style connectors, most 68K Macintoshes did not. Instead the Modem
and Printer
ports both were designed as round Mini-DIN sockets with 8 pins each (Mini-DIN 8 female). A male cable connector looks like this:
| Pin | Signal | Description |
| 1 | DTR | Data Terminal Ready - Handshake from Mac to PC |
| 2 | DSR | Data Set Ready - Handshake from PC to Mac |
| 3 | TXD | Transmit Data - from Mac to PC |
| 4 | GND | Ground |
| 5 | RXD | Receive Data - from PC to Mac |
Nine pin serial in the form of DB9 has been the de-facto standard for serial ports within the PC world for a long time. Even nowadays some computers offer these on board and expansions cards are available for all current systems. It is still used heavily in industrial setups. Pins are counted as indicated below.
| Pin | Signal | Description |
| 1 | DCD | Carrier Detect Input |
| 2 | RXD | Receive Data - from Mac to PC |
| 3 | TXD | Transmit Data - from PC to Mac |
| 4 | DTR | Data Terminal Ready - Handshake from PC to Mac |
| 5 | GND | Ground |
| 6 | DSR | Data Set Ready - Handshake from Mac to PC |
| 7 | RTS | Request to Send |
| 8 | CTS | Clear to Send |
| 9 | RI | Ring Indicator |
While Mini-DIN 8 male to DB9 female adapters are still available, they may not work in this special case because they are usually designed for entirely different scenarios. Since I was not able to find a correct adapter I decided to build one myself. Because two computers were supposed to be connected, a cross-link adapter was needed. Therefore lines for both Handshake and Transmit/Receive Data were to be reversed. The diagram below illustrates an adapter to male Mini-DIN 8.
I acquired a new Mini-DIN 8 extension cable and a neat female DB9 connector with screw terminals. The Performa came with a StyleWriter II and included its original printer cable (male to male). So my adapter would be used with the printer cable and the female half of the new extension cable would become the actual adapter. Confusing, I know. My serial cable connection was to comprise the printer cable and an extension (a.k.a. my adapter), so it was - regarded as a whole - a Mini-DIN 8 male to DB9 female adapter.
With the adapter the essential requirement was met - and i could connect both computers physically. To make them talk to each other compatible software was needed on both ends. Kermit - a project initiated at Columbia University, NY - has been around since 1981 and was and is available for a large number of platforms. With The New Open-Source Kermit Project it still is actively improved upon.
MacKermit, an application for the Motorola 68000-based Macintosh, ran happily on my Macintosh System 7.5.3. Luckily it fit on a 1.44M floppy diskette and therefore could easily be installed on the Macintosh via drag and drop. I set-up Kermit 95 (C-Kermit 10.0 Beta.11, published in August 2024) on a PC - a Pentium III with Windows 98 SE - as this was the latest version. There even was a 32-bit installer!
Kermit95 comes with a graphical user interface (GUI). You can use the dialer to set up connections you want to use regularly. Additionally you can go straight to the console and set u an ad-hoc connection. If you are planning on uploading files to the PC side, I strongly recommend setting auto-download
to on, as this makes things much easier.
This is how I prepared and started my connection in Kermit's console:
> cd e:\temp # choose the directory where your files are
> set port com1 # select port, here COM-1
> set speed 57600 # the speed that works with both your machines
> set carrier-watch off # assume there is no carrier signal
> set terminal type tty # change terminal type to tty
> set parity none # no parity
> set terminal bytesize 8 # 8-bits in terminal
> set command bytesize 8 # 8-bits for command
> set terminal remote-character-set ascii # define terminal character set ASCII
> connect # start the connectionYou can download the dialer entry I setup for serial transfers during this experiment.
MacKermit is similar to Kermit95, general setup, however, is more simple. Starting with Settings
, I selected Modem
as the adapter was plugged into the corresponding connector on the back of the Mac. I also disabled carrier watch
and set the speed of the serial connection to the maximum 57600 baud. The only thing left was to select my working directory under File-Transfer
Set directory
(one downloads to it and uploads from it). With Get file from server
and Send file
I was able to download from and upload to the PC.
For optimal readability the above screenshots of MacKermit were taken from a Macintosh Performa 630 emulated with Basilisk II.
When disconnect when finished
is enabled and a transfer fails you will have to connect
Kermit 95 again. If auto-download is not enabled the PC will present you a Safe file as...
dialogue while you may sit in front of your Macintosh wondering why your transfer is not starting.
With the settings above I was able to transfer about 2.5 MB in an hour - yes hour, not second. This would have been pretty good for transfers over the internet in the mid nineties. If you happen to have a computer around with which you can prepare diskettes for an old Macintosh, that is a faster option but comes with its own downsides. If you haven't, do not want to swap disks for some time or your machines are further apart, then serial transfers are a good way of getting data on and off your old Macintosh. By the way: you do not need a computer with a traditional serial port built in as the other end point. There are USB-to-serial adapters available which can be used with any modern system.
Many SBCs like the Raspberry Pi can be set up for serial communication via UART. Also an adapter cable for the Raspberry's GPIO can be made relatively easily. With the flexibility and connectivity of a Raspberry Pi 4, for example, this could become a very neat solution.
Another valid route is networking. LocalTalk is worth a closer look but I do not expect faster transfers. And to access network resources on a modern LAN a bridge between a LocalTalk network and an Ethernet or a wireless network would be needed. The most expensive option would be a COMM-port Ethernet card for the Performa, of course. This would offer convenience and increased speed over serial transfers. However, in this scenario you still require a compatible service on another computer on the network to exchange files - while a ftp server would cater basic needs the neatest solution would be an Apple file server which is discoverable by and can communicate with Mac OS 7 clients. A Netatalk setup as described in part two of the G4 Series should actually do the trick.
Here are some websites related to this topic which helped me on my quest.
On Time/ Travel Sketches