May 2009 Archives

North Star Horizon

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One of the retrocomputing projects I’ve been working on lately is finally taking shape — the restoration/construction of a North Star Horizon S-100 bus computer system.


I’ve been building this system up from parts, as the 1977 vintage Horizon chassis — though complete with a battered wooden chassis cover, HRZ-MB-3 motherboard and power supply — had been stripped of its complement of S-100 cards and diskette drives.


The HRZ-MB-3 motherboard supports up to twelve S-100 cards (only six are populated with connectors on my unit), and has a built-in serial terminal interface at the rear. I was able to track down a Horizon ZPB-A2 Z-80A Processor Board, Horizon RAM32 Memory Card and Horizon MDC-A4 Micro Disk Controller from additional eBay auctions. For the diskette drives, I went with Shugart SA-450s which are close to original spec (SA-400).


Next steps involve locating a new fuse holder for the power supply as the existing holder’s retention cover and fuse are missing. I also need to locate an appropriate floppy cable and operating system diskettes.


Perhaps later down the road, I’ll attempt to rebuild or repair the wooden chassis cover as it is in pretty poor condition. The original Horizon chassis cover was constructed of cheap veneer covered plywood (kind of a seventies thing), so repair would involve stripping the old veneer away, filling areas with wood putty and then applying fresh new veneer. It might just be easier to build a new cover to similar specifications out of quality wood, though it would be arguably less authentic I suppose.

Anyway, I’ve had fun putting this together so far; kind of a treasure hunt locating all the parts to form a mostly complete Horizon. Hopefully I can get it to a state where it will actually run once again!

Update: I noticed another NorthStar Horizon chassis has shown up on eBay. This one is missing the motherboard which may be a show stopper for many, but does have the Shugart SA-400 floppy drives, drive cable and a complete power supply. Kind of interesting - not sure why the Horizons that turn up these days are stripped, but I have seen a number of loose Horizon boards as well (including a bare motherboard last month) so it may not be too difficult to rebuild if one is so inclined.

Epson PX-8 Geneva


While catching up on older episodes of Earl Evans’ always entertaining Retrobits Podcast, he mentioned a company selling new, still-in-the box Epson PX-8 “Geneva” laptops. My interest in the machine was piqued after listening to additional shows which discussed both the PX-8 in general as well as covered his quest to get a virtual floppy system up and running for the machine.


Amazingly enough, though these podcast episodes were recorded nearly three years ago (in the summer of 2006), Star Technology continues to stock the new-in-box PX-8s for $99 each. Around the same time, I watched a used PX-8 go for $140 on eBay, which sweetened the deal.


I bought a unit, along with a new Software Library package containing Portable WordStar, CalcStar and Scheduler for an additional $15.

Earl provides a great overview of the machine in his podcast, which is of course recommended listening. But in a nutshell, the PX-8 Geneva is a Z80 compatible, CP/M 2.2 based laptop with an 80 column by 8 line LCD display. It sports a respectable 6-8 hours of battery life on a single charge.


Commercial software is provided by way of ROM modules that plug into a bay on the underside of the machine. Out of the box, the unit comes with CP/M utilities and BASIC on ROMs — and as mentioned previously, Portable WordStar, CalcStar and Scheduler are available in ROM format as well. User storage is provided via an internal microcassette drive, but an external cable can be built to interface with a PC-based virtual floppy emulator for more robust storage.


It’s a neat little machine! The display is surprisingly usable - having the full 80-columns does make a huge difference. The keyboard also has a nice, solid feel. It’s certainly a neat way to experience a vintage CP/M machine that doesn’t take up a lot of space, and it’s certainly fun breaking the seal on a machine that was “new” in 1984 … in 2009.

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This page is an archive of entries from May 2009 listed from newest to oldest.

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