HOW TO "READ" FM TUNER SPECIFICATIONS 7t ioiiIc $ WORLDS LARGEST-SELLING ELECTRONICS MAGAZINE JANUARY 1975/75¢ PROJECT BREAKTHROUGH! 1Mild's First Minicomputer Kit to Rival Commercial Models... ALTAIR 88U0" SAVE OVER $1000 { A LTA 1R 8800 PAX: 1. let F In au an {0 l O, OS T- f a, ci tt n Os S i Q 11 . `/ MOO J t '4, _ , - . r . _ !w tn. LIS All tl U at = Al {{ U /11. At at {O O 6 G .. t O u 11 tt 1! 11 uMu ' AlOS tnr uuw aMut . sr MOW .a a.Ma4ai ' . in 9 - t- 4 ALSO IN THIS ISSUE: An Under -$90 Scientific Calculator Project o,ae . CCD's-TV Camera Tube Successor? . r'`?99` Thyristor-Controlled Photoflashers ;- TEST REPORTS: lSt Technics 200 Speaker System le Q 0'© Pioneer RT-1011 Open -Reel Recorder Tram Diamond í,6. 3:cr Nvs .aa,© - é f g COGN311 Aw 551 Edmund Scientw sr .1121abEi 1 i4 Hewlett-Packar , t 9teat C6451CC479 kxG' 96IC4£ 18101 AmericanRadioHistory.Com Popular Electronics PC 1117/ JANUARY, 1975 TESTED EXCLUSIVE! ALTAIR 8800 The most powerful minicomputer project ever presente -caM be built for under $400 á: . ;' --¢-^-. ., - .-r= ALTAIR 8800 ui1 PIOr MM. °,ei r i1 Our eUI ,;11.101.- 30 IR' It ° 05 04 U n- 11 00 5, n t [ ,'r` q [1. Q.,' Q.-.. ó ' ri '11 43 ' gout 3301-I@ IM R] !It III MO 7, M 03 tl,ai' II II°. 'lb II. C' , 0 O . U,.G t! , , U, l ° ' 1 , , . ' ' - ' .1 IS ...se . I 1 1- 1 S 1^ I 0 - r 10 /1 p r5 e-, .INAull, _ y 1 "-----11 4% 4% ":-....:174111.UAfíS N 331 IrOi . U1/II: 0/71IM - O(IOS+, Iltlr ° IVrIR A01 a0R Y01Ki d BY H. EDWARD ROBERTS AND WILLIAM YATES THE era of the computer in every tral processing unit is a new LSI chip home-a favorite topic among that is many times more powerful than science -fiction writers-has arrived! previous IC processors. It can ac- PROCESSOR DESCRIPTION It's made possible by the POPULAR commodate 256 inputs and 256 out- Processor: 8 bit parallel ELECTRONICS/MITS Altair 8800, a full- puts, all directly addressable, and has Max. memory: 65,000 words (all directly blown computer that can hold its own 78 basic machine instructions (as addressable) against sophisticated minicomputers .compared with 40 in the' usual Instruction cycle time: 2 ps (min.) Inputs and outputs: 256 (all directly ad- now on the market. And it doesn't cost minicomputer). This means that you dressable) several thousand. dollars. In fact, it's can write an extensive and detailed Number of basic machine 'instructions: in a color TV -receiver's The has price class program. basic computer 78 (181 with variants) -under $400 fora complete kit. 256 words of memory, but it can be Add/substract time: 2 ps The Altair 8800 is not a "demon- economically expanded for 65,000 Number of subroutine levels: 65,000 strator" or souped -up calculator. It is words. Thus, with full expansion, up to Interrupt structure: 8 hardwire vectored the most powerful computer ever pre- 65,000 subroutines can all be going at levels plus software levels sented as a construction project in any the same time. Number of auxiliary registers: 8 plus electronics magazine. In many ways, it The basic computer is a cómplete stack pointer, program counter and represents a revolutionary develop= system. The program- can be entered accumulator Memory type: semiconductor (dynamic ment'inielectrónic design and think= via switches located on the front or static RAM, ROM, PROM) ing. a in panel, providing LED readout bi- Memory access time: 850 ns static RAM; The Altair 8800 is a parallel 8 -bit nary format. The very -low-cost termi- 420 or 150 ns dynamic Ram word/16=bit address computer with an nal presented in POPULAR ELEC- instruction cycle time of 2 µs. Its cen- TRONICS last month can also be used. JANUARY 1975 33 AmericanRadioHistory.Com matter) is shown in Fig. 1. It consists of the following subsystems: PARTS LIST CPU. The heart of the computer is the CPU, or central processor unit. See fig. 2. The CPU performs all the calculations, generates system tim- C1, CS 'to C13- 10.1-µF disé capacitor ing, and makes all decisions. Of par- C2 --0.01-µF disc capacitor ticular importance are the decisions C3, C4-100-pF disc capacitor the CPU makes concerning what de- C14 to C20-0.001-µF disc capacitor vice should have access to the data 1C1-8080, central processing unit IC (Intel) buss. It makes these decisions by IC2 to ICS 74L74 IC { sending status information at the be- Fig. 1. Basic block 106 to IC 14-8T97 IC ginning of each computer cycle, diagram of computer tel- IC15, IC17-7402 IC ling the memory and the input/output parts and operation. IC 16, IC32, IC33-7404 IC . what to expect for the rest of the cycle. 1C18 to IC20, IC51-74123 IC The CPU contains the program ' IC21-7473 IC timer, sometimes called the P counter. 1C22 to 1C24, IC50 7400 IC This device keeps track of the current IC25-7430 IC In an upcoming issue, we will de- location in the memory that the proc- i; IC 26-7410 IC scribe how to build a low-cost CRT - essor is using. Also located in the CPU 1C27 to IC31, IC39 to IC41-7405 IC type terminal that can be used with the is the arithmetic unit. 1C34, 1C35-8111 IC IC36-74L30 IC computer and can also be mated with The CPU used in the 8800 computer; IC42 to IC49-74L00 IC any time-sharing computer by tele- the Intel 8080 LSI chip, is relatively ex- 1052-7406 IC phone. pensive in quantities of It one. was IC53 to IC58- 8111 IC (optional) selected, however, because it serves I.ED1 to LED36-Panel-type, red light-; About the Computer. A computer is to create a minicomputer whose per- emitting diode a basically piece of variable hardware. formance competes with current (Note: Following are resistors 1/2 -watt, By changing the bit pattern stored in commercial minicomputers. In prac- 10% tolerance) - the memory, the hardware (electronic tice, a lower -performance processor Rl, R3, R9 to R31, R56-1000 ohm circuitry) can be altered from one type would have been adequate for the ma- 'R2, R4, R7, R8-330 ohm - R5, R33 to R37-2200 ohm of device to another. When the bit pat- jority of the tasks the user might wish 1 R6-7500 ohm tern, and thus the hardware, is to initially define. But the problem with R32-100 ohm changed, we have what is referred to the lesser -power approach is that rela- R38, R48 to R55-10,000 ohm as "software." Any type of variable in- tively little money would be saved, and R39-200,000 ohm struction (programming)-such as it would be doomed to near -future ob- R40 to R47-470 ohm. Basic, Fortran, Cobol, Algol-is gen- solescence for practical purposes. R57 to R92-220 ohm erally classified as software. Our intent here was to produce a 51 to S16, S25-Spst miniature toggle To cause it to vary the hardware, you processor with more than enough switch must communicate with the compu- power to handle any job. 517 to S24-Spdt spring -loaded, momen- ter. In the case of the 8800, this is done Still another consideration was tary -action miniature toggle switch by setting the bit pattern on the front- programming. The larger the instruc- KTAL-2-MHz crystal . Misc.-Metal case; power. supply panel switches in accordance with a tion set, the easier the computer is to (see text); line'cord; multiconductor ribbon t. set of instructions (provided with the program. The 8080 chip has 78 in- cable; mounting hardware; etc. Intel 8080 LSI chip). For example, the solder; structions, which is almost twice that Note: The following items are 8800 computer will available automatically add of the next power level CPU available from< MITS,. Inc., 6328 Linn N.E., when a specific bit pattern (10000010) (Intel's 8008), which is really designed Albuquerque,- NM 87108 (Tel.: 505- is received. By setting address and for use as a buffer. 265-7553): partial kit No. 8800PK (in- data switches, a complete program of The CPU contains eight general- cludes pc boards and all electronic com- up to 78 steps in the basic computer purpose registers, P counter, arithme- ponents (but not case, switches, or can be inserted into the processor. If tic unit, accumulator, stack pointer, power supply),..$298; complete kit No. 8800K extensive programming is to be per- instruction decoder, and miscellane- (contains all parts, including ready -to -use case, switches, and power formed, an assembler or higher lan- ous timing and control circuits. The supply), $397; Completely assembled guage is used. With an assembler, the arithmetic unit is of special interest and tested Model 8800A computer (in- person doing the program simply because it contains the circuitry re- cludes'90-day warranty), $498. Prices do types the word "add" on the device. quired to perform arithmetic in both not include postage or delivery charge. (In Basic and Fortran, a + is used in- decimal and binary formats. ' Both kits include detailed assembly and stead.) The stack pointer is the register that _ operating manual..A FREE set of etch- Fundamental programming con- keeps track of the subroutine ad- = ing and drilling guides, component- cepts are simple enough to master in a dresses. The 8800 computer is capa- placement diagrams and miscellaneous relatively short time.