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.

PCMCIA 1.0, SRAM and linear flash cards

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Although mounting remote HDDs over a serial cable to my Olivetti Quaderno was a nice solution, it was not very fast. I wanted to add persistent storage using a PCMCIA card, but Quaderno has just PCMCIA 1.0. I used to work a lot with PCMCIA, but it was always the newer standard (2.0) typical for 386/486 laptops. PCMCIA 1.0 does not support IO devices (so no ethernet cards) or CompactFlash cards (as they are IO cards in the ATA mode). PCMCIA 1.0 can work only with linear memory mapped cards. For linear flash cards, there were two incompatible standards (FTL and MS FFS). SRAM cards had just a single standard. In addition to all of this, simpler devices (industrial, embedded) required attribute memory on the card in order to work at all (fortunately, this laptop supports full Card Services and does not need it).

I took a 4MB PCMCIA SRAM expansion from my Amiga 600 and put it in Quaderno. The ROMDOS drive contains a Microsoft program called MEMCARD.exe (very similar to FDISK.exe, but for early PCMCIA cards), so I used it to format the card, rebooted the machine and got 4MB of persistent storage (the SRAM card has a battery to retain the data even after removing the card from the computer).

These early PCMCIA cards don’t work in Windows out of the box. However, there is already a DOS driver included in Windows 9x. You just need to add two lines in the config.sys and you can use the SRAM card in a “more modern vintage computer” (it still allows you to use the slot with other cards and use hot-plug features). Btw these direct mapped SRAM cards have one big advantage – they are super-fast.

I know it’s almost 30 years late, but I finally understood, how these old PCMCIA devices work…

Olivetti Quaderno PT-XT-20 (1992) – part 2

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You might think that the machine is useless without a working HDD and no floppy drive, but that is not true. Quaderno has a small bootable “ROMDOS” drive with basic system files, COMMAND.COM, a RAMDISK driver (up to 320KB of EMS memory can be used and you still have full 640KB of conventional memory) and Interlink software. This drive is interesting, because it acts like a read-write one. You can edit config.sys and autoexec.bat (the changes are there even after shutdown, if the CMOS battery is ok or AC is connected). You can even copy files there, but if it’s more than a few KB, the system will crash hard (requiring you to
reinitialize the ROMDOS).

With Interlink, you can mount remote HDDs over a serial port. I used it to run VC (Volkov Commander) to edit the config.sys (no EDIT.COM in ROMDOS) and enable the RAMDISK driver. After this, I had my small but fast local storage (non-persistent) and everything bigger was started directly out of the remote HDD from another computer. This is a good way to test the computer before fixing the HDD or installing a flash/SRAM card in PCMCIA 1.0.

Pocket Computing

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HP 200lx (1994) and Poqet PC (1989) are x86/XT compatibles with DOS in ROM. Poqet PC is more like a standard PC and has a better keyboard. On the other side HP is loaded with full-featured productivity programs (PIM, Lotus spreadsheet, word processor, scientific and financial calculators…) and a special easy-to-use graphics environment.

Libretto 70CT (1997) runs standard Windows 95/NT. Except for the size this is a normal laptop. Toshiba somehow managed to squeeze a 2.5-inch hard drive and the Pentium CPU in a package with the size of Windows CE handhelds.