Section 2 - Commodore Computers

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128 COMPUTE! May, 1982, 1982. IssueI ~ue 24 speed: 1. I. Diskettes that don't turn freely inside their disk jackets significantly slow down the drive. Be sure you make the test with the "loosest" diskette you can find. diskette you can find. 2. Drives seem to turn fastest when they are first turned on and slow. down slig htly as they first turned on and slow down slightly as they warm up. We don'l don't know why this is true. Adjusting Drive Speed Before you attempt to adjust your drive, we must caution that the operation described here may void any warranty youu have for your Atari drive. Even if the drive is out of warranty, Alari Atari does not recom mend that users attemptLO to adjust the speed of their drives. A special speed test diskette and an oscilloscope are necessary, they maintain, to prop erlyy set the drive speed. Neither the author, Quality Software, nor COMPUTE! magazine Gi cann assume any responsibility for damage caused to your drive while attempting to make a speed adjustment. We do know that hundreds of Atari owners are already acUusting adjusting the speed of their drives with no known negative results. Atari does provide an 8 10 Service Manual results. Atari does provide an 810 Service Manual for $30 to anyone who insists on doing their own repairs. Write to Atari Personal <strong>Computers</strong>, <strong>Computers</strong>. 1395 Bonegas Borregas Avenue, Sunnyvale, CA (attn: Lupe SOto). Soto). If I f youu decide you want to make a speed acU adjust ustment, carefull y fo llow the fo llowing steps: ment, carefully follow the following steps: 1. I. Be sure you have a cleann working environment so that dust, hair, etc. e lC. will not get into the disk drive. Turn offthe power to the disk the disk drive. Turn off the power to the disk drive. 2. You will need a pen knife, a small to medium sized phillips head screwdriver, , and a small SIOl slot screwdriver. r. 3. Using g the pen knife orr similar instrument nt or strong fingernails, il lift off the four plastic stick-on screw hole covers on the top of the drive. 4. Using g the phillips screwdriver, remove the four screws that secure the drive cover to the base of the drive. 5. Carefully y lift the cover off the drive and set it aside. 6. With the drive facing you, locate the drive speed potentiometer, which is a nylon wheel with a slot in it, in the back of the drive to the left side. We have found two different colors off potentiometers, white and blue. 7. Using the SIOl slot screwdriver, turn the tuner in a clockwise direction to slow it down, counterclockwise to speed it up. You will have to experiment until you have arrived at the right speed. 8. Replace the drive cover before testing the drive, but don't screw it back on until you have the drive speed properly adjusted. the drive speed properly adjusted. The BASIC Program Looking again at Program 1, I, we will explain how the BASIC program works. Lines 100 and 1100 read in data statements 1000 LO to 1080, POKEing 73 values into the reserved RAM area staning starting at memory location 1536 ($600). These 73 bytes comprise a machine language routine that deter r mines the amount of time it takes the drive to rotate 100 times. Lines 120 and 130 clear the video screen and ask the user to input the drive number. Line 140 pokes the indicated drive number into memory location 1610 ($64A). Line 150 calls the machine language routine. Afterr returning to the BASIC program, the time lime it took the drive to rotate 100 times is in memory mory locations 1611 and 1612 12 ($64B,$64C). These values are read into A and B by line 160. The value A is a number ranging from 0 LO to 255 that is incremented 60 times a second and the 255 that is incremented 60 times a second and the value e B is a number that is incremented increnlented once for every time the value of A reaches 256. Thus line 170 computes the elapsed time in minutes by computing it in sixtieths of a second and dividing by 3600. Line 180 computes RPM LO to the nearest unit by dividing 100 (the number of revolutions) by MINUTES. The 0.55 permits proper roundoff. Line 190 displays the result o n the video sc reen. Line 190 displays the result on the video screen. The Machine Language Program Program 2 is a listing of the source code forr the machine language program aand is provided for those familiar with machine language. The first instruction (line 0010) I 0) is required to clean up the stack for reentering ring BASIC. Lines 0011 to 0014 set the sector number to 1. Lines 0015 toOO 0017 l7 setup a buffer area at $500 into inLO which the data from seCLO sectorr I will be read. Lines 0018 and 0019 set the drive number r to the value specified by the user. Lines 0020 and 00211 specify a read operation. Lines 0022 and 0023 will cause sector I LO be read five times to 0023 will cause sector 1 to be read five times to ensure that the drive is up LO to full speed. Lines 0024 and 0026 perform these five reads by calling the a nd 0026 per form these fi ve reads by calling the resident disk handler ($E453). Lines 0027 and 0028 request 100 more reads. Lines 0029 and 003 1 zero out two of the Atari's Lines 0029 and 0031 zero out two of the Atari's timer r bytes ($13 and $ $14). Lines 0032 to 0034 perform 100 reads. T he n lines 0035LO 0038 save the elapsed time in ALOC AND BLOC ($64B, S64C). $64C). Line 0039 returns control to the BASIC program. perform 100 reads. Then lines 0035 to 0038 save the elapsed time in ALOC AND BLOC ($64B,
VOUNEED YOU NEED SpeedRead+ • Optimized Systems Software, the company that brought you BASIC A+ and OS/A+, proudly presents another "PLUS". "PLUS", • SpeedRead+ is the world's first speed reading tutor designed for use on your personal computer. computer, • SpeedRead+ begins with training your eyes and mind to function as the incredible precision machine they were meant to be. be, • SpeedRead+ goes beyond mere words —- it trains you to recognize phrases and columns instantly —- it exercises your peripheral vision —- it increases your comprehension. comprehension, • SpeedRead+ matches your pace —- now and in the future. future, AVAILABLE NOW! AVAILABLE NOW! For 16K ATARI" ATAAI' computers with disk, Introductory Price """ " "',"""""""""',.,,' $59.95 $59,95 Coming soon for APPLE IP. II' , Inquire about availability of TRS-80" TAS-80' and cassette versions. versions, SEE YOUR DEALER TODAY! SEE YOUR DEALER TODAY! Call or write for a descriptive brochure of SpeedRead+ ,- and other fine OSS products, such as OS/A+, , BASIC A+, , and TINY C\ C' , ATARI. AlARI, APPLE II, TRS-80, lRS·BO. and TINY C are trademarks of 01 Atari. Alan, Inc., .. Apple Computer. Computer, Inc.. Inc" Radio Shack, Shack. and Tiny C Associates, respectively- respectively. SpeedRead+ d+ is a trademark of 01 Eagle Software and Optimized Systems Software. Optimized Systems Software, Inc., .. 10379 10319 Lansdale unsdale Ave., Cupertino, Cupertino. CA 95014, 95014. (408) 446-3099 446·3099
Page 1 and 2: 1\ MALA Educational Programs M\~ Fo
Page 3 and 4: May. 1982. Issue 24 COMPUTEI 101 Ma
Page 5 and 6: • the battle for the moons of Jup
Page 7 and 8: May, May. 1Q82lssue 1982, Issue 24
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Page 11 and 12: • Announcing the Printing Breakth
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Page 15 and 16: APPLE • ALTOS • ATARI • MAXEL
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Page 29: THEE MOSAIC 32K RAM FOR ATARI 32K R
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Section 2 - Commodore Computers

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