1·1· 'c 0
HORIZON
More and more, you see the North Star H O R IZON computer at work: in busi
ness , research, and education. Its high performance qualifies the HORIZON for demanding professi onal applica
tions. Over 1 0,000 users during the past two years have proven that North S t a r h ar d w a r e h a s t h e r e l i a b i l ity for day- i n , day-out com puting. The H O R IZON is now a serious candidate for any small system i nstallation.
SOFTWARE IS THE KEY TO HORIZON MATURITY North Star BASIC and DOS have been used to d evelop h u n d reds of com
mercial prog ram packages. These packages establish that North Star software has the completeness and conve n i e nce necessary for serious program development. Because of the many i n de pe ndent ve ndors offering software using North Star BAS IC and DOS, the H O R IZON owner now has the widest selection of software in the m icroco m p u t e r i n d ustry! S oftware available includes: word processing, g eneral ledger, accou nts payable/
receivable , m a i l i ng l ist process i n g , i nve ntory a n d i nc o m e tax prepar
ation. Program development systems s u c h as a s s e m b l e r s , d e b u g g e rs , editors, P I LOT a n d FORTRAN are also available.
EXPAND YOUR HORIZON T h e basic H O R IZO N com puter i n cludes a Z 8 0 m icroprocesso r , 1 6 K bytes of RAM memory, an 1/0 i nterface and one Shugart minifloppy disk drive.
The H O R IZON can be expanded to 60K bytes or more of RAM, three disk drives, and three 1/0 inter
faces. Performance can be enhanced by t h e ad dition of the North Star hardware floating point board.
Also, S-1 00 bus pro
d u c t s f r o m o t h e r man ufacturers m ay be used to expand the H O R IZON.
For m o re i nforma
t i o n , cont act yo u r local computer store.
NoRTH * STAR CoMPUTERS
2547 Ni nth Street
Berkeley, California 947 1 0 ( 4 1 5} 549-0858
Circle 285 on inquiry card. BYTE December 1978 29
Fu nction Program storage Tape storage Program counter Head
Sequenci ng Display I nitial izing tape Saving tape Debuggi n g design
is to represent a signed d isplacement from the current program counter, as Millen suggests in his article. I n hardware, this wou ld require adding a 6 bit adder between the address bus and the program counter, plus some temporary latches to hold the results. I n software, a store instruction must be changed to an add instruction. I n hard
ware, the board must be modified to accom
modate the new circuitry, and the clock re
adj usted. I n software, under M I KBUG, the change can be made with seven keystrokes.
If this system were to be widely dis
tributed , complete documentation would have to be written. The hardwired approach requires a circuit board layout, a schematic d iagram , parts list and written commentary.
In the software version, comments in the program serve to document the system, along with a written commentary.
The software approach allows a building block technique. The program may be easily combined with other programs. The external programs need to know only the addresses of the various blocks in the universal Turing machine program's logic. The universal Turing machine circuit would have to be mod ified to adapt it to other equipment.
The software version uses M I KBUG's load and d u mp routi nes to save the tape contents, but this would have to be a special ly con
structed circuit for the hardwired design.
The design, implementation and testing times of the software version were two, one and two hours, respectively. I don't know the exact times required for the hardware approach, but they should be at least several times more than the software approach.
I n order to build the hardwired circuit, the experimenter must obtain al l the cir
cuitry, a circuit board, wire, power supply, etc, which may or may not be used in future experiments. However, once you have a microcomputer to work with , no extra items
Hardware Version Software Version
2 1 02 Memory locations hexadecimal 00 thru 7 F
2 1 02 Memory locations hexadecimal 80 thru F F Two 74 1 6 1 s Memory locations hexadecimal F B thru F C Three 74 1 9 1 s, 7474 Memory locations hexadecimal FD thru F F 7404, 741 61 ' 741 54 Conditional branching
7 segment LED M I K B U G print/punch command 74 1 57 , 7400,switch M I K B U G l oad command
M I K B UG pri nt/punch command Logic probe and M I K B U G break command osci lloscope
Table 2: Correspondence chart of the functions of the two approaches and the means with which they are implemented.
30 December 1978 © BYTE Publications Inc
are needed and the computer is usable for any other projects without losing th·e ability to reload the universal Turing machine program.
This exam ple cannot be taken as a com
plete treatment of the trade-offs of the two approaches. Each designer m ust judge the merits of an approach accord ing to the particular needs of the problem to be solved . If the universal Turing machine were to be mass-produced for tim e-critical operations, the h ardware approach woul d be best. If the design is to be used for the Sunday afternoon project of a m icrocomputer enthusiast who already has a system, the software approach would be best.•
Operating the Turing Machine 1 . Put your program i n the state stor
age area. N ote that the add ress of each state is twice the state n u m ber.
2. Initial ize the tape storage area. You may put your tape anywhere in memory as long as you set the tape head pointer to the proper initial address. Location hexadecimal 0080 is convenient.
3. I n itial ize the program counter. Put 00 in location hexadecimal OOFB, and the first address in the Turing m achine in lo
cation hexadecimal OOFC. This m ust be the actual memory address (twice the state number).
4. I n itial ize the mask. The mask se
lects which bit of the byte pointed to by the head pointer to operate on. I t must be composed of seven 0 b its and a single 1 bit. 01 is a reasonable starting value.
5. I nitial ize the head pointer. This is the address of the byte in memory to be considered as the head of the tape. It must point to the tape storage area.
6. Set your M I KBUG start address to hexadecimal 0200, press G (for go), and away it goes.
R E F E R E NCES
1 . Millen, J, "A U niversal Turing Machine,"
December 1 976 B YTE, page 1 1 4 .
2. Ralston, A, and Meek, C (editors). Encyclo
pedia of Compu ter Science, Petrocelli-Charter, New York, 1 976, pages 1 43 2 thru 1 437.
3. Shannon, C E, and McCarthy, J (editors).
Automata Studies, Princeton University P ress, Princeton NJ, 1 956.
Double Capacity
The DOUBLER - Micromotion's latest advance in floppy disk technology - doubles the capacity of floppy disk systems.
Over 500 K!3ytes are recorded on each side of on 8" disl�.
This means bigger files for more powerful systems.
Double Speed
Data transfer with the DOUBLER is twice as fast -500 Kbits
per second. And since there is twice as much data on each trocl�. your drive steps only half as much - so your system runs foster than it ever has before!
Increased Reliability
That's right - even better reliability. Why? Because we did it the 1 13M way. 1 13M designed 2D formatting - so it has to be reliable. Micromotion's innovative, state-of-the-art de
sign incorporates write precompensotion electronics and a phose lock oscil lator on a single, all digital, S-1 00 circuit
board. So we guarantee the DOUBLER will be more de
pendable than your present single density controller - and we worontee the DOUBLER for a full year.
Unbeatable Convenience
It couldn't be easier to step up to double density. The DOUBLER operates automatically in either single or double density. Just insert a diskette and you're running properly. You
con transfer files between single or double density diskettes without any software or hardware changes - or even
oper-and the software is all ready to go. An onboord 2708 EPROM
contains the bootstrap. There's even jump-on-reset circuitry so you con operate without a front panel . And , of course, we include utilities to format disl�ettes.
Universally Versatile
The DOUBLER will operate with all industry-standard mini and full-sized drives. And it will work in any 8080 or Z-80
S- 1 00 computer operating at 2 to 4 MHz. The DOUBLER will support up to four double or single headed drives.
Fully Compatible
The DOUBLER is compatible with CP I M * version 1 .4. If you hove a CP I M * 1 .4 system, just odd our C!310S - or you con buy our ready-to-boot version. I nstall the new controller, connect any terminal to the RS-232 interface, and boot off your new double-sized, double-speed system. You still con use all your old software without any changes.
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All Micromotion products ore fully assembled, thoroughly tested, include complete documentation, and ore priced for value:
DOUBLER double density controller
MEGABOX dual drive double density system ZEPHER - Per Sci double density system Z- PLUS - MEGABOX 32 KZ-80 computer
$ 495.
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2,595.
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ate with one single and one double density diskette. Available
Installation is a snap. There's a hardware UART on board The DOUBLER is available NOW at your local computer store.
Micromotion Inc. 524 Union Street San Francisco California 94133 / 415 398-0269
Where there's always more in store.
Circle 223 o n i nq u iry card.
'CP/M is a trademark of Digital Research.
BYTE December 1978 31