'NOVEMBER 19 7 G'E)OLZDt1à1Y www.americanradiohistory.com SWTPC announces first dual minifloppy kit under $1,000 Sire CT64::..... 5WÌreMINIFLOPPY SYSTEM SilAV 6800 c DISK SYSTEMEfN Del Now SWTPC offers complete best -buy computer system with $995 dual minifloppy, $500 video terminal/ monitor, $395 4K computer. $395 4K 6800 Computer The SWTPC 6800 comes complete with 4K memory, serial interface, power supply, $995 MF -68 Dual Minifloppy chassis, famous Motorola MIKBUG® You need dual drives to get full benefits mini -operating system in read -only from a minifloppy. So we waited to offer a memory (ROM), and the most complete floppy until we could give you a dependa- documentation with any computer kit. Our ble dual system at the right price. growing software library includes 4K and The MF -68 is a complete top -quality 8K BASIC (cassettes $4.95 and $9.95; minifloppy for your SWTPC Computer. The paper tape $10.00 and $20.00). Extra kit has controller, chassis, cover, power $500 Terminal /Monitor memory, $100/4K or $250/8K. supply, cables, assembly instructions, two The CT -64 terminal kit offers these Other SWTPC peripherals include highly reliable a premium features: 64- lines, Shugart drives, and character $250 PR -40 Alphanumeric Line Printer diskette with the Floppy Disk Operating upper /lower case letters, switchable con- (40 characters /line, 5 x 7 dot matrix, System (FDOS) and BASIC. (A disk floppy trol character printing, word highlighting, 75 line /minute speed, compatible with is no better than its operating system, and full cursor control, 110 -1200 Baud serial our 6800 computer and MITS /IMSAI); the MF -68 has one of the best available.) interface, and many others. Separately $79.50 AC -30 Cassette Interface System MF -6X -64 is 12 MHz An optional $850 kit expands the the CT $325, the CT-VM (writes /reads Kansas City standard tapes, system to four drives. $175. monitor controls two recorders, usable with other computers); and other peripherals now Enclosed is: $250 for the PR -40 Line Printer and to come. $1 990 for the full system shown above $79.50 for AC -30 Cassette Interface (MF -68 Minifloppy, CT -64 Terminal with Additional 4K memory boards at $100 CT-VM Monitor). Additional 8K memory boards at $250 Southwest Technical $995 for the Dual Minifloppy Or BAC # Exp. Date EEITI Products Corp. $325 for the CT -64 Terminal Or MC # Exp. Date 219 W. Rhapsody, San Antonio, Texas 78216 $175 for the CT-VM Monitor Name Address London: Southwest Technical Products Co., Ltd. $395 for the 4K 6800 Computer City State Zip Tokyo: Southwest Technical Products Corp. /Japan www.americanradiohistory.com Circle 136 on inquiry card. You can now have the industry's finest microcomputer with that all- important disk drive YOU CAN GET THAT ALL -IMPORTANT SOFTWARE, The professional - TOO grade microcomputer for professionals Loading your programs and files will take you only a few seconds with the new Cromemco Z -2D computer. You can load fast because the Z -2D comes equipped with a 5" floppy disk drive and controller. Each diskette will store up to 92 kilobytes. Diskettes will also store your pro- grams inexpensively -much more so than with ROMs. And ever so much more conveniently than with cas- settes or paper tape. The Z -2D itself is our fast, rugged, ADVANCED CONTROLLER CARD Shown with optional bench cabinet professional -grade Z -2 computer The new Z -2D is a professional equipped with disk drive and con- system that gives you professional troller. You can get the Z -2D with performance. either single or dual drives (dual In the Z -2D you get our well - We're able to put all of this in- shown in photo). known 4 -MHz CPU card, the proven cluding a UART for the CRT interface Z -2 chassis with 21 -slot motherboard on just one card because we've taken CROMEMCO HAS THE and 30 -amp power supply that can the forward step of using LSI con- SOFTWARE handle 21 cards and dual floppy You can rely on this: Cromemco drives with ease. troller circuitry. is committed to supplying quality Then there's our new disk con- STORE/ FACTORY software support. troller card with special features: Contact your computer store or For example, here's what's now Capability to handle up to 4 Cromemco factory now about the available for our Z -2D users: disk drives Z -2D. It's a real workhorse that you CROMEMCO FORTRAN IV COM- A disk bootstrap Monitor in a can put to professional or OEM use PILER: a well -developed and power- 1K 2708 PROM now. ful FORTRAN that's ideal for scien- RS An -232 serial interface for Kit: Z -2D with 1 disk drive tific use. Produces optimized, relo- interfacing your CRT terminal (Model Z2D -K) $1495. catable Z -80 object code. or teletype Assembled: Z -2D fully assembled CROMEMCO 16K DISK BASIC: a LSI disk controller circuitry and tested (Model Z2D- W) $2095. powerful pre -compiling interpreter Additional disk drive with 14 -digit precision and powerful (Model Z2D -FDD) $495. I/O handling capabilities. Particularly Z -2 USERS: Your Z -2 was designed with the future SOFTWARE suited to business applications. in mind. It can be easily retrofitted (On standard IBM -format CROMEMCO Z -80 ASSEMBLER: a with everything needed to convert to soft -sectored mini diskettes) macro -assembler that produces relo- a Z -2D. Only $935 kit; or $1135 for 16K BASIC (Model FDB -S) $95 catable object code. Uses standard assembled retrofit package. FORTRAN IV (Model FDF -S) $95 Z -80 mnemonics. Z -80 Assembler (Model FDA -S) $95 Cromemco Gin c or p or a t e d Specialists in computers and peripherals 2400 CHARLESTON RD., MOUNTAIN VIEW, CA 94043 (415) 964 -7400 Circle 40 on inquiry card. www.americanradiohistory.com TV DAZZLER To make your computer more useful- a wide choice of memory, I/O, CPU Your computer's usefulness de- grammer. Uses high -speed 2708 eras- (Model TRT -K): $195. Assembled pends on the capability of its CPU, able PROMS. A must for all com- (Model TRT -W): $295. memories, and I/O interfaces, right? puters. Will load 8K BASIC into RAM JOYSTICK. A console that lets So here's a broad line of truly in less than a second. Kit (Model you input physical position data with useful computer products that lets BSK -0): $145. Assembled (Model above Model D + 7 A/D card. For you do interesting things with your BSW -0): $245. games, process control, etc. Con- Cromemco Z -1 and Z -2 computers. 16K CAPACITY PROM CARD. Ca- tains speaker for sound effects. Kit And with your S- 100 -compatible Al- pacity for up to 16K of high -speed (Model JS -1 -K): $65. Assembled tairs and IMSAIs, too. 2708 erasable PROM. Kit (Model (Model JS -1 -W): $95. CPU 16KPR -K): $145. Assembled (Model 16KPR -W): $245. PROFESSIONAL QUALITY Z -80 MICROPROCESSOR CARD. You get first -class quality with The most advanced p.P card avail- I/O INTERFACES Cromemco. able. Forms the heart of our Z -1 FAST 7- CHANNEL DIGITAL - Here are actual quotes from ar- and Z -2 systems. Also a re- direct ANALOG I /O. Extremely useful ticles by independent experts: "The placement for Altair /IMSAI CPUs. board with 7 A/D channels and 7 Cromemco boards are absolutely Has 4 -MHz clock rate and the power D/A channels. Also one 8 -bit par- beautiful" . "The BYTESAVER is Z µP of the -80 chip. Kit (Model ZPU- allel I/O channel. Kit (Model D + tremendous" . "Construction of K): $295. Assembled (Model ZPU- 7A -K): $145. Assembled (Model D Cromemco I/O and joystick are out- $395. W): + 7A -W): $245. standing" . "Cromemco periph- MEMORIES TV DAZZLER. Color graphics in- erals ran with no trouble whatso- 16K RAM. The fastest available. terface. Lets you use color TV as full - ever." Also has bank -select feature. Kit color graphics terminal. Kit (Model Everyone agrees. Cromemco is (Model 16KZ -K): $495. Assembled CGI -K): $215. Assembled (Model tops. (Model 16KZ -W): $795. CGI -W): $350. STORES /MAIL 4K RAM. Bank -select allows ex- DIGITAL INTERFACE (OUR NEW So count on Cromemco. Look pansion to 8 banks of 64K bytes TU -ART). Interfaces with teletype, into these Cromemco products at each. Kit (Model 4KZ -K): $195. As- CRT terminals, line printers, etc. Has your store. Or order by mail from sembled (Model 4KZ -W): $295. not one but two serial I/O ports and the factory. THE BYTESAVER - an 8K capa- two 8 -bit parallel I/O ports as well We wish you pleasure and suc- city PROM card with integral pro- as 10 on -board interval timers. Kit cess with your computer. Cromemco in c or p or a t e d Specialists in computers and peripherals 2432 CHARLESTON RD., MOUNTAIN VIEW, CA 94043 (415) 964-7400 Circle 40 on inquiry card. www.americanradiohistory.com FUI NOVEMBER 1977 In the Queue Volume 2 Number 11 Foreground 10 MEMORY MAPPED 10 PUBLISHERS Hard ware -Ciarcia Virginia Peschke Manfred Peschke 50 USING INTERRUPTS FOR REAL TIME CLOCKS EDITOR IN CHIEF Real Time Techniques -M F Smith Carl T Hclmcrs I r PRODUCTION MANAGER 68 DOES ANYBODY KNOW WHAT TIME IT IS? Judith Havcy Peripherals -Grappel CIRCULATION MANAGER Gregory Spitzfaden 72 ADDING AN INTERRUPT DRIVEN REAL TIME CLOCK ASSISTANT PUBLISHER Real Time Systems -Sneed Debra Boudricau EDITOR 76 FLOATING POINT ARITHMETIC Christopher P Morgan Soft ware -Hashizume CO -OP EDITOR Scott Morrow 80 BUILDING A COMPUTER FROM SCRATCH PRODUCTION EDITORS Hard ware -Jones Karen Gregory Nancy Salmon 94 A 6502 PERSONAL SYSTEM DESIGN: KOMPUUTAR ADVERTISING Hardware-Brader Debra Boudricau, Director Noreen Bardslcy 146 IMPLEMENTING AN LSI FREQUENCY COUNTER Virginia Peschke Hardware -Lynne EDITORIAL ASSISTANT Ingrid Nyland 150 SWEET16: THE 6502 DREAM MACHINE PRODUCTION ASSISTANT Software- Wozniak Cheryl