Pecos SWW<>The Northstar Horizon Microcomputer

The Northstar Horizon Microcomputer
A True Classic

Welcome to the Pecos Buffet! Grab a plate and help yourself.

A Little Bit of This.
The School of the Personal Microcomputer
The Northstar Horizon S100 Bus Z80 Processor Microcomputer
The S100 Boards - 16 KB RAM, Z80 Zilog Processor, Floating Point Math, and Micro Disk Controller Boards

A Little Bit of That.
The Micro-Term Monitor and Keyboard
The Comrex Letter Quality Daisy Wheel Parallel Printer
The IP225 Dot Matrix Serial Impact Printer
The Original Owner Manuals

The Buffet Desert and More from Your Gracious Waiter
Editorial Privilege

The School of the Personal Microcomputer

In 1980 I had moved away from home and found myself stuck in a dead end job. I had a BSBA degree with MIS (Management Information Systems) as my major from the University of Arizona. I wanted to find a job in my career, but those jobs were few and far between in Tucson, Arizona and my starting salary would be less than my then current job. So I decided that I had two options, go back to school and get a Masters degree or buy a microcomputer and get some hands on training.

I got the microcomputer. I decided on a used Northstar Horizon, cost $3000.00. Now that may seem like a lot of money, and it was in 1980 dollars, but new, the 4x16 KB RAM boards alone would have cost $3200! That's right, I have an ad from a magazine quoting the price of one 16 KB RAM board at $795.00.

I enjoyed writing BASIC programs. I wrote a slot machine game, a word processor, and a payroll accounting system. This was before the days of integrated graphics, but with a little bit of clever planning, you could get ASCII characters to build pseudo graphics.

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The Northstar Horizon Microcomputer

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The Power Supply

Part	Specification
Transformer	HRZ-T1
15 Volt Electrolytic Capacitor	180,000uf +11 Volts DC (+- 15%)
25 Volt Electrolytic Capacitor	11,000uf +22 Volts DC (+- 15%)
25 Volt Electrolytic Capacitor	8,900uf -22 Volts DC (+- 15%)

Shugart SA400 Minifloppy Diskette Storage Drive Specifications

Dimensions

Width	Height	Depth	Weight
5.75 in	3.25 in	8.00 in	3 lbs

Capacity

Soft Sectoring	Hard Sectoring
80.6 KB	72.03 KB

Performance Specifications

Transfer Rate	Latency (Average)	Access Time (Track to Track)	Access Time (Average)	Access Time (Settling Time)	Head Load Time	Disc Motor Start Time
125.0 Kb/Sec	100 ms	40 ms	463 ms	10 ms	75 ms	1 sec

The front panel is clean with a logo and power LED. This may be the first personal computer with two built in diskette drives. The Northstar Horizon is renowned for its hardwood case. The S100 bus card cage holds twelve S100 boards, including the Z80 processor board.

The power supply is not modular like the modern personal computers. The three large, medium and small can capacitors and transformer are huge and built into the basic Northstar Horizon model.

I read that powering up an old Northstar Horizon can cause the large capacitors to literally catch on fire. This computer has not been used in more than 20 years.

If the box is marked correctly, this computer shipped as a Horizon-1 with 16 KB of RAM.

The microcomputers of the late 70's had no hard drives. External Winchester-technology drives were optional and very expensive. An 18 MB (that's MegaBytes not GigaBytes!) hard disk drive was available for the Northstar Horizon. It weighed 80 pounds and was huge when compared to the drives you see today - 9" x 20" x 26".

In order to get the computer to do something useful, a 5 1/4" floppy diskette with Northstar DOS had to be inserted into the leftmost diskette drive before start-up. At that point, you could load BASIC or another program to do some real work.

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The S100 Boards

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Board Notes

16K RAM Board The boards are manually selectable into one of four banks of 16K to total 64K. The board pictured here is selected for the third 16K bank. Each 16K RAM board contains 32 MK 4027 -3 MOS IC chips.

Z80A Processor Board The large IC chip is the 8 bit 4MHz Z80A microprocessor. Although it is hard to read, this appears to be the MOSTEK MK3880N version of the Z80A CPU.

Floating Point Board From the Northstar FPB-A Revision 5 manual: "The FPB is a microprogram controlled processor designed specifically to perform high speed decimal floating point arithmetic operations. The unit is implemented entirely from medium and small scale TTL integrated circuits and PROM memory. All data paths in the microprocessor are 4 bits wide thus enabling processing one decimal digit at a time."

Micro Disk Controller Controls up to four micro (5 1/4") floppy diskette drives.

Board	Notes
16K RAM Board	The boards are manually selectable into one of four banks of 16K to total 64K. The board pictured here is selected for the third 16K bank. Each 16K RAM board contains 32 MK 4027 -3 MOS IC chips.
Z80A Processor Board	The large IC chip is the 8 bit 4MHz Z80A microprocessor. Although it is hard to read, this appears to be the MOSTEK MK3880N version of the Z80A CPU.
Floating Point Board	From the Northstar FPB-A Revision 5 manual: "The FPB is a microprogram controlled processor designed specifically to perform high speed decimal floating point arithmetic operations. The unit is implemented entirely from medium and small scale TTL integrated circuits and PROM memory. All data paths in the microprocessor are 4 bits wide thus enabling processing one decimal digit at a time."
Micro Disk Controller	Controls up to four micro (5 1/4") floppy diskette drives.

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The Micro-Term Act-IV Terminal

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Item Specification

Access Mode Local or Remote

Baud Rates (I/O) 300, 600, 1200, 2400, 4800, 9600, 19200

Baud Rates (Printer - Optional) 110, 300, 600, 1200, 2400, 4800, 9600
Duplex Mode Half or Full

EIA 25 Pin Connectors (2) AUX, I/O

Item	Specification
Access Mode	Local or Remote
Baud Rates (I/O)	300, 600, 1200, 2400, 4800, 9600, 19200
Baud Rates (Printer - Optional)	110, 300, 600, 1200, 2400, 4800, 9600
Duplex Mode	Half or Full
EIA 25 Pin Connectors (2)	AUX, I/O

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The Printers

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The Comrex Daisy Wheel ComRiter

Item	Specification
Print Wheel	96 pedals/wheel Cassette Type
Print Rates	16 Characters Per Second
Carriage Motion	Bi-directional, logic seeking
Carriage Return Speed	1,000 ms Maximum
Characters Per Line	132 characters (1/10"), 158 characters (1/12"), 198 characters (1/15")
Ribbon	Cassette Type One Time Film Ribbon - 120,000 Characters Maximum
Ribbon	Cassette Type Multi Strike Film Ribbon - 500,000 Characters Maximum

The Integral Data Systems BrighterWriter IP225 Impact Printer

Item	Specification
Print Head	7 x 7 Dot Matrix Impact
Print Rates	83, 100, 120, 165 Characters Per Second*
Baud Rates	110, 150, 300, 600 or 1200
Printable Characters Per Inch	8.3, 10, 12 or 16.5

* "However, the maximum sustained print rate is generally just under one-half the print rate to account for print head reversal and return time." From the The BrighterWriter IP-125/225 Impact Printer Owner's Manual.

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The Original Owner's Manuals

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Manual Name	Picture
The North Star May 1980 Product Catalog
The North Star May 1980 Product Catalog Back Cover
The North Star May 1980 Product Catalog Pages 6-7
The North Star System Software Including North Star Basic Manual
The North Star Z80A Processor Board Manual
The North Star 16K Ram Board Manual
The North Star Double Density Diskette Drive Manual
The North Star Floating Point Board FPB-A Manual
The Zilog Z80/Z80A CPU Technical Manual
The Shugart SA400 Mini-Floppy Diskette Storage Drive Manual
The Micro-Term Act IV Owner's Manual
The Micro-Term Act IV Technical Manual
The BrighterWriter Impact Printer Product Catalog
The BrighterWriter Impact Printer Manual
The Comrex Daisy Wheel Printer Manual
The North Star December 1979 Newsletter #4
The North Star Dimension IBM Compatible Multi-User System Poster

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Editorial Privilege

This is the section where I am allowed to stray from the facts, give my opinions and feelings and make speculations and inferences.

Note that the misspellings in the quoted text/specs are as written in the manuals. Some things never change.

The purchase of the Northstar Horizon led to a job at a local small business, Digitgraph, where I got my start in the MIS field. There a very smart engineer by the name of Steve Brault discovered from data sheets that the 4K RAM chips that I needed for the RAM boards could be replaced with the more common and inexpensive 16K chips.

The computer had fallen victim to electrical shorting from the only spot in our rented condo where water leaked in over the power plug doing quite a number on the various boards. The computer was fixed at a local repair shop, but the RAM was never quite the same. If you look closely on some of the pictures of the boards you will see pencil marks on some of the chips put there during the repair.

All in all, the computer was a lot of fun and a great learning experience at a time when personal computers were virtually unheard of. I learned by using the Northstar Horizon that the personal computer was more than just a toy and would eventually play a major role in the business place.

Even more fun than the Northstar Horizon was the Northstar Advantage. It was the successor to the Horizon and its main interest to me was its graphics capabilities. Now this wasn't the fancy color graphics that you see today on all personal computers, but simple green screen graphics. A local computer store allowed me to borrow the manual and I wrote a very cool '21' card game. I remember sitting out in the spring Tucson weather mapping out the details of each face card. Now that was fun and the results were very professional. I still have the program, but I wonder what the store did with their version of the game.

Waiter! I want to look at my buffet choices again.

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© Copyright 2007-2015 Alan Norton None of the content may be used or reproduced without written authorization from Alan Norton.

The Northstar Horizon Microcomputer A True Classic

The Northstar Horizon Microcomputer

Click on thumbnail picture for a larger image

The Power Supply

Shugart SA400 Minifloppy Diskette Storage Drive Specifications

Dimensions

Capacity

Performance Specifications

The S100 Boards

Click on thumbnail picture for a larger image

The Micro-Term Act-IV Terminal

Click on thumbnail picture for a larger image

The Printers

Click on thumbnail picture for a larger image

The Comrex Daisy Wheel ComRiter

The Integral Data Systems BrighterWriter IP225 Impact Printer

The Original Owner's Manuals

Click on thumbnail picture for a larger image

The Northstar Horizon Microcomputer
A True Classic