null-modem

First steps with my Tandy TRS-80 Model 100

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I recently acquired a shiny Model 100 portable with necessary accessory. I played a bit with the machine before cleaning it and I was a bit surprised that it could retain data in the RAM disk for minutes after disconnecting the power. That gave me the impression that there was a backup battery inside, which scared me enough to open the machine immediately… and yes, although the battery still provided some voltage, it started destroying itself and the computer. I removed the residue from both the backup battery and the battery compartment for AA cells and cleaned the rest of the machine. It looks almost like new now.

I have to say that I am very impressed with the Model 100. The user experience is closer to professional computers of that time than home 8-bit machines. The programs in ROM can read/write the same files, switching between them is fast and there is even a shared clipboard. I particularly like the built-in terminal emulator with handy access to download/upload features and easy configuration. This was a true mobile companion for those working on the road and accessing the company minicomputer over modem.

My version does not have the modem, but at least the null-modem communication works flawlessly. I think I should install an old UNIX somewhere and try accessing it like in the old days. Somebody even created a Model 100 termcap definition file, so it is possible to use control functions of its terminal emulator in UNIX.

Backing Up DD Floppies

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I was asked by my manager to download data from multiple boxes full of floppy disks he used in the early 90s. I’m used to people at work asking me for help with old UNIX systems, but reading 5.25-inch floppies is here for the first time. He used to be a musician when he lived in Israel and used his 386 PC as a sequencer with an E-mu Proteus/1 external wavetable synthesizer.

I picked my Vienna 286 computer to read the floppies. It’s quite a high spec machine with an 8MHz CPU, math coprocessor, Hercules-compatible Graphics and 1.5meg ISA RAM card… and it’s my only computer with a 5.25-inch drive. If you ask why I removed the CRT before I started copying the files, ugly mold smell goes from it every time it’s turned on and I hate it. I rather configured the machine to work in a headless mode (straight boot into Microsoft InterLink Server) and accessed the drives from a laptop over a null-modem cable.

Mac OS 7.1 CZ, Serial Cable and File Share

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I’ve installed a new “hard disk” in my PowerBook 100 a few months ago. However, until now, there was no time to install an operating system other than the primitive System 6.0.8E that I used in the floppy-only mode. My goal was to have a Czech version that would allow me to read and write documents with our unique letters like Ř/ř. With a help of my friend, I got the floppy images of Mac OS 7.1 CZ and was able to copy them on real floppies (using my modern iBook G4 and a generic USB drive).

Working with old Macs can be painful due to use of file metadata (called resource forks) that can be lost very easily. Old Mac apps insist on this metadata and refuse to open a file if metadata is lost. Having a modern Mac is always handy to prevent these situations.

I don’t have a Mac serial cable. However, I recently bought two adapters for the conversion from Mac/SGI 8-pin mini-DIN to PC DB9. Connecting these adapters to a standard null-modem on both sides worked well and I was able to copy programs and documents from another old Mac. I’ve also managed copying files from/to a modern Windows PC. I pack the files into a ZIP file (to preserve resource forks) inside a Mac emulator and copy it using ZMODEM.