PAHI2= MASS

EDN'sAll-Star PC incorporates several mass-storage devicesthat provide flexible information storage and easydata interchange among PCs. We frequently crossedthe thin linebetween the leading and the bleedingedges of data-storage.technologyaswe. tested variousstorage devices, host adapters, and peripheralcontrollers. What we learned applies to all typesof computersystems, notjust PCs.

I nU's originalModel5151 PC provideddata stor- | l"g.onsingle-sided,160k-bytefloppydisksand I on audio cassettetapes. The floppy-disk-drive'r" capacitywas mediocre,even by early 1980sstan- vl' dards, and the 200 bytes/secaudio-cassette inter- . facewas a joke. Fortunately,mass-storage capacity t, ;:d:i,,l:'fii$i," ifiif, x'-'ili:'*a'"#TJ';, ry data, PC-compatible hard disks store hundreds and even thousands of megabytes, and tape drives store gigabytes. EDN's All-Star PC incorporateseight mass- --i t storage peripheral devicesmanaged by three con- troller or host-adapter cards (Fig 1). Each of these three mass-storagesubsystems- , SCSI, and WORM (write- once, read-many)optical drive-has uniquecapabilities. The floppy-disksub- i systemsupports four floppy-diskdrives, which furnish convenient. removable data storage and permit standardized il STEVEN H LEIBSON, Senior Regional Editor data interchangewith other PCs. floppy-disk drive, the All-Star PC wastough because most PC floppy- The SCSI subsystemcontrols two would not be able to duplicate disk controllers manage only two 330M-bytehard disks for the com- floppy disks directly; it would have floppy-diskdrives. The All-Star PC putet's primary data-storageneeds to temporarily store the informa- would require a floppydisk control- and a 2.5Gbyte tape unit for archi- tion being copied on a hard disk ler card that could manage four val and backupstorage (Fis 2). Fi- while the source and destination floppy-disk drives and support the nally, the PC's opticalWORM drive disks were swappedin the floppy- PC's floppy-diskformats. The Com- provides indelible file storage on disk drive. Becauseof an idiosyn- paticard IV from MicroSolutions lG-byte cartridges. cratic aversionto 2-step floppy du- ComputerProducts met these re- Floppy-disk drives are the one plication, I decidedearly on that the quirements. common element in every PC's All-Star PC would incorporatefour Table I lists the PC floppy-disk mass-storage repertoire. IBM's floppy-disk drives: two 5%-in. and formats that the Compaticard IV floppy formats swept away the mi- two 3%-in.drives. supports. The Compaticard IV, crocomputerindustry's hundredsof Meetingthat 4-driverequirement alongwith one 5%-in.high-capacity 6%-in. floppy-disk formats devel- drive and one 8%-in. high-capacity oped for the CPAI{ operating sys- drive, can read any standard PC tem. However,even IBM's l60k- floppy-disk format. The Compati- byte disk format didn't last long. card IV also supports other types ,'sDOS 1.1 introduceda of floppy-disk drives, such as the 320k-byte, double-sided format. now archaic 8-in. units, and can DOS 2.0 added hierarchical file store 2.8M bytes on certain }L/t-in. structures to the disk, bumpedthe drives that accept a ne\Mtype of single-sidedfloppy-disk capacityto floppy disk basedon barium-ferite l80k bytes, and increasedthe dou- media. The All-Star PC incorpo- ble-sidedformat's capacity to 360k rates a 2.8M-byte floppy drive-an bytes. The 360k-byteformat's rapid FD-236I from Teac America Inc. proliferation consignedthe earlier This drive can read and write stan- PC floppy formats to oblivion. dard 720k-and 1.44M-bytePC disks The next mqjor change in PC and can also use barium-fenite floppydisk formats occured when disks. The All-Star PC incorporates IBM introduced its PC/AT with three other floppy-diskdrives from l.2M-byte, "high-density," llr-in. Teac-two FD-55GFR5%-in., high- floppy-disk drives. Then came 3%- density drives and one FD-235HF in. floppy-disk drives that stored gr/b-in. drive. Thus, the All-Star ?20k bytes, followed by the intro- PC's full complementof drives in- duction of IBM's PS/2 cludes two 5%-in. and two 3%-in. and 1.44M-byte, Srrh-in. drives. units. Over a 9-yearspan, the.PC, which had unified the industry's floppy- Twisted cablesmake it tough disk formats, evolvedits own collec- TWofactors in IbM's floppy-disk- tion of incompatibleformats. subsystem design complicated ef- The All-Star PC needed to ac- forts to put four floppy-disk drives commodate these various floppy in the All-Star PC. The first is a formats for maximumcompatibility very peculiar floppy-disk-driveca- with other PCs. It neededat least llcven mau-rtoragepcrlpheralr cram the All- ble for the PC. The cable includes two floppydisk drives: a irA-in., Strr PC'r l0 half-helghtdrlve bayr. hon top a twist that interchangesthe drive- l.ZM-byte drive and a Tr/z-in., to Dottom,the perlpheralrInclude a 2.5G-byte selectand motor-enablesignal lines tape drlve, tno 5.25-ln.and two 3.5-ln.flopry- 1.44M-byte drive. However, with dh& drlves, and tm 330M-bytehuddtrL betweenthe cable'stwo drive con- only one lVq-in. and one Tr/z-in. drlvee. nectors.firis cute schemesimplifies

108 EDN March29, 1990 9omprti.,rd tv 83li;,li?*"n-,;",ffrXlii s+,?,f,[f,gHi:]&lly],,.rr. eAi 6is).?rt'_l&6:

system conflguration by allowing you to set all of the floppy-disk- drive selectjumpers to address 1, uz,riqi*$*r., but it negates the original floppy- disk-drivecable's ability to address four drives. Fig 3 illustrates how the Compaticard IV circumvents fffit'f**ilr"tr."',"* IBM's eccentric floppy-disk-drive cable limitations by splitting the four drives under its control into two pairs. Each pair of floppy-disk drives connects to the controller with a separate floppy-disk-drive cable. However, solving the hardware Compaticard IV and supplying a limitations of IBM's floppy-disk- loadable device driver for the extra subsystem design doesn't fix the two drives. The devicedriver adds This is not merely a hypothetical second problem-BlOS (basic I/O the extra floppy-disk drives onto problem. The All-Star PC includes system) limitations. Most PC the end of the existing drive-desig- a pair of enormoushard-disk drives mother-boardBIOS ROMs control nator chain. Thus, if your system and initially used Microsoft's DOS only two floppy-disk drives. Al- has four floppy-disk drives and two 3.3, which accommodates disk though the Compaticard IV man- hard drives, the first two floppy driveswith capacitiesto 32M bytes. ages as many as four floppy-disk designatorsare A and B, the hard- The AII-Star PC's hard-disk drives drives, IBM's original PC/AT com- drive designators are C and D, and have a formatted capacity of 330M puter did not. Consequently,com- the third and fourth floppy designa- bytes each. DOS 3.3's solution to puters and BIOS ROMs patterned tors are E and F. This scheme this mismatchwas to create l0logi- after the PC/AT support only two works for most PCs, but can cause cal drives out of eachphysical drive. floppy-disk drives. MicroSolutions problemsfor systemsthat useenor- As a result, the first hard-disk drive skirted this problem by incorporat- mous hard-disk drives and older transmuted into logical drives C ing a floppy BIOS ROM on the versionsof DOS. through L; the second hard-disk drive became drives M through V. The Compaticard IV therefore as- signed designators W and X to the €:d secondpair of floppies. DOS only handles26 logical drives (A through Z), leaving only two drive designa- tors for use with other storage de- *q vices.Because the All-Star PC was going to have an optical WORM disk drive, there was actually only one drive designator left to play with. ea Designator-relatedproblems arose with a disk-cachingprogram called PC-Cache,part of the PC ToolsDe-

Sculptureby KathyJeffers/Sculpture Photog- raphy by Chrir Vincent.Photography by The Fig l-Three subsyrtemsprovide the All-StarPC's mass-storage capabilities: a floppy ruboyotem, PhotoWorks and StevenLeibson unless other- a SCSIsubsystem, and a WORM(write-once, read-many) optical-disk rubrystem, wire noted.

EDN March 29, 1990 luxe packagefrom Central fers. The All-Star PC could have audio tape) drive, but one wasn,t Point Software Inc (Beaverton, OR, used drives with larger capacities available in time for this project. (503)690-8090). PC-Cache improves (some 5%-in. SCSI hard-disk drives The EXB-8200stores 2.5G bytes on hard-disk performance, but it inter- such as Micropolis Corp's 1bg0 se- one 8-mm videotape cartridge, yet fered with the Compaticard IV's ries now have capacities in excess the entire unit, including an inte- floppy-disk device driver. After of lG byte), but we couldn't find gral formatter/controller, occupies loading the program, I could no any \Y+in. hard drives that were the space of a full-height, 5%-in. longer read or write from the two faster than the Wren Runners. For drive. It also employs helical-scan \r/z-in. floppy-disk drives, W and X. this project, speed reigned over ca- recording. Suspectingthat the program cache pacity, becausea pair of BBOM-byte The Wren Runners and the EXB- was inter{ering with the device drives seemedto provide all the ca- 8200 require a SCSI host adapter driver, I instructed PC-Cache to ig- pacity the All-Star PC required. for operation, but becauseof expe- nore drives W and X. It couldn't. No sane system integrator would diency (or perhaps becauseof a lack however,because it recognized only omit a way to back up 660M bytes of foresight), the PC's BIOS only the first 16 drive designators, A of on-line data. Because the Wren works with a Western Digital through P. Clearly, PC-Cache and Runners employ SCSI llo, I WD1003 controller card and ST-b06 DOS 3.3 couldnot be used together planned to use a SCSI-basedtape hard-disk drives. Tape drives are on the All-Star PC. You,ll find the drive that could back up both hard- somewhat less trouble becausepC solutions to this problem in Part 4. disk drives on just one tape car- BIOS ROMs don't support them at As long as PC-Cache wasn't acti- tridge. These constraints left only all. Therefore, there are no com- vated, the floppy-disk drives one choice: Exabyte's EXB-8200 patibility problems to overcome. worked fine. Even without a cach- cartridge-tape subsystem. I briefly PC disk controllers that don't imi- ing program, the All-Star pO's considered using a DAT (digital hard-disk drives, a pair of Seagate Technology's SCSI-based Wren Runners, are very fast. The hard- llriue disk drives have an average-seek- FD.5SGFR57r'in' ttini Flonry'Disk time rating of 12.8msec and a max! mum track-to-track seek-time rat- ing of 4.8 msec. (Both ratings in- clude controller overhead.) They also support SCSI transfers at burst rates to 4.?M bytes/sec for synchronous transfers and ZM bytes/sec for asynchronous trans- 3lfi3ltt (unrormatted):1'6M' IXJ$iit (rormatted'Dos): ifrXnSPB['il^Ft*': sook'3ook' liTff"n:u3u,rg,,,0 msec SIDES:2 ^^^ .r^^^r, f^rmats: 1.2M and li?hiil;l+':qtrilF*i",:+*tri["ft*L*]$3;'sil'ff"fS,d

110 EDN March29, 1990 Table1-Compaticad lV floppy-diskformats Formatted capaclty Flrstsupported Drlve Sides ln DOgveBlon: 5Vt ln, 360k 2 2.m 48 lpi s20k 2 1.10 2 slded 180k 1 2ffi 160k 1 100 St/t in, 800k 2 Proprietaryto Compaticard 96 tpl 360k 2 2.00 2 slded 320k 2 1.10 180k 290 160k 1 1.00 tate the PC/AI's original disk con- 5Vt ln, 1.2M 2 3.00 troller card do have compatibility 96 tpl 8mk 2 Pmpri€taryto compalicard problems. However, the rewards of 2 elded 360k 2 2.00 Hlghcapaclty 920k 2 1.10 using the SCSI bus are worth the 180k 1 2.CX) risks of incompatibility. 160k r.00 in. 1.2M 2 Propriotaryto Compaticard I 't30 2 3lded 250k 1 SCSI provides many benefits 3Vzln, 720R 2 3.20 SCSI compatibility gives you a 2 *lded wide choice of high-performance 31hln, 1.4M 2 3.30 2 slded 720k 2. 3.20 storage peripherals, including hard- Hlghcapaclty disk drives with a range of capaci- 31hln, 2.8M 2 Proprietaryto Compaticard ties (from less than 100M bytes to 2 slded 14M 2 330 Exendeddonslty 720k 2 3.20 more than lG byte), high-capacity floppy-disk drives, and tape drives. One industry group, the CAM (CommonAccess Method) Commit- the storage peripherals immedi- lecting the SCSI host adapter: tee, is developing specificationsto ately, not when CAM-compatible speed and compatibility. Because solve the driver problems for SCSI- products finally appear (see box, the Wren Runners are so fast. a basedproducts, but the All-Star PC "CAM: A common accessmethod slow host adapter would introduce needed a SCSI host adapter that for SCSI"). a bottleneck in the SCSI subsys- would work with the soft,wareand There were two criteria for se- tem. And the compatibility objec- s6:

:*-€

-*:

Fig 2-One SCSIhost adapter,an lN-2000from AlwaysTechnology, controls the All-Star PC'r two 330M-bytehard-dirk drives and the cartridge tape drive.

EDN March29, 1990 111 tive presented an even more com- DMA to achieve high transfer ager, problems arose, which even- plex problem. The SCSI frrmware speeds. Even aft,er confining the tually forced me to choosean alter- and software supplied with the host AHA-1540A to its slowest DMA native SCSI host adapter (see box, adapter had to be compatible with transfer rate to prevent it from "Lost in (memory) space"). the variety of DOS extenders and overmnning the All-Star PC's operating systemsthat the All-Star memory subsystem,it still achieved Climbing out of the box PC would use. In addition, the host transfer rates of almost l.3M bytes/ The lessonslearned from working adapter had to support the Wren sec, according to version 2.8 of a with the AHA-1540A led away from Runners and the Exabyte EXB- disk-performance test program SCSI host adapters that employed 8200. from Core International (Boca Ra- first-party DMA. EDN Regional After testing host adapter cards ton, FL, (407) 997-6055).However, Editor Maury Wright helped find from several manufacturers, I se- after installing Quarterdeck Office a product that offered format com- lected Adaptec's AHA-1540A. The Systems' (Santa Monica, CA, (213) patibility with the AHA-1540A AHA-1540A employs first-party 392-9701) QEMM memory man- (eliminating the need to reformat

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Fig 3-The PC's twiated floppy-dltk cable catr only handle hro floppy{lok drlvee, eo the All-Star PC'a floppy-dirk controller employs two such cables to control lts four floppy drives.

EDN March29, 1990 FD-?3ilEFllz.in.ificro Ffoppy.lffskDrive ;:j:"Tojga Inc,7730 rere_ ;,filtiiiS"I;;yo4;i"o

STATSI tfitJ]t (un the harddisk drives), had the i,CI rormatted): 2M, requisite operating-system and de- vice drivers available, didn't use first-parby DMA, and promised good performance. That product is i5$ii*ttg"**""*" Always Technology's IN-2000 AT Ifl'ff.?.l"%'.:.'?u,niE1* SCSI Host Adapter. Onceinstalled in the All-Star PC, SIDES:2 the IN-2000 worked as advertised. The machine booted without refor- matting the hard-disk drives. In ad- iil'"tJ,,:i"Tfr dition, the board proved compatible 1'#i,iij'*lil.fi#!'fiillil",,lr*TS"iT#T*"#*, with QEMM's memory-mapping abilities, indicating that the first- party DMA problem was indeed hard-disk and tape drives. Moving solved. However, after a keyboard the tape drive to SCSI address 4 The Core test claimed that the reset (invoked by pressing the con- solved the problem by separating IN-2000 initially transfened 970k trol, alt, and delete keys simultane- the tape drive and the hard-disk bytes/sec, roughly 257o less than ously), the PC locked up shortly af- drives at addresses0 and l. With- the AHA-1540A. This is a respect- ter initializing the SCSI drives. Al- out the address gap, the IN-2000 able speed, but the Wren Runners ways quickly determined that the was attempting to initialize the tape can do better, as earlier experi- problem was causedby the consecu- drive as if it were a disk drive, and ments with the AHA-1540A tive SCSI addressesI used for the as a result, lockedup. proved. A searchfor the I/O bottle-

CA]VI:A common accessmethod for SCSI The PC'slack of adequatedrivers for SCSI host the software-accessmethods it developsshould be adaptersand peripheralscaused many of the All- extensibleto other computersystems as well. Star PC Project'smass-storage problems. Periph- For the PC, the committeeis approachingthe eral vendorsrely on host-adaptervendors to write problem at the lowest level. Most PC operating- the peripheral drivers becausethose drivers are al- systemsoftware can control disk drives attached ways specificto the host adapter. The host-adapter to a WesternDigital WD1003hard-disk controller vendorscan't possiblywrite softwaredrivers for becausethat is the controllerIBM shippedwith the every conceivableSCSI peripheral;they're too busy PC/AT. The CAM Committee'sATA (AT Attach- writing drivers that coupletheir boardsto the most ment) specdefines a standardmethod that allows popularPC operatingsystems. Consequently, every SCSIhost adapters to mimicthe WD1003by emulat- SCSIhost adapterfor the PC workswith only a few ing its register set. This approaeheliminates the PC operatingsystems and supportsonly a subset needfor specialSCSI drivers.Perceptive Solutions of the availableperipherals. The CAM (Common Inc (DeSoto,TX, (214)n4-6774) offers a caching AccessMethod) Committee is trying to eradicate disk controller,the Hyperstore1600, that has a this problem. WDf0B emulationmode along the lines of CAM's Formedin 1988,the committeeis developingsev- ATA spec.The committeeis also developingan en- eral specificationsthat will allow vendorsto write hancedAT attachment(EATA) specificationthat oneset ofdrivers for everyoperating system, host allows a driver to take advantageof SCSI features adapter,and peripheraldevice. It includesrepresen- not availablethrough the ATA emulationmode. For tatives from a wide crosssection of peripheral,host- more information about the CAM Committee,con- adapter,and computervendors. Currently, the com- tact its chairman,I Dal Allen, 14426Black Walnut mittee is focusingon the needsof PC systems,but Ct, Saratoga,CA 95070.Phone (408) 867-6630.

EDN March 29. 1990 113 neck (with the intent of boostingthe BIOS ROM back into the IN-2000, vided relative performance data SCSI subsystem's performance), we changed a PLD on the Cheetah that helped improve the All-Star coupled with two experiments, ex- Gold 425 mother board to speed its PC's performance. posed the culprit. For the first ex- expansion bus from 6 to 8 MHz. With the SCSI performanceprob- periment, Always supplied a re- That experiment had no effect on lem supposedlylicked, I loaded a vised BIOS ROM for the IN-2000 the Core test, proving that the suite of tape--sofbwarepro- that reprogrammed the board's "slow" ISA bus was not interfering grams, supplied by Novastor Corp SCSI protocol chip, a Western Digi- with the All-Star PC's disk-trans- (Westlake Village, CA, (818) 707- tal WD33C93, to eliminate hand- fer-rate efficiency. Of course, abso- 9900),onto the system. When the shake delays that the chip was gen- lute test numbers don't tell you All-Star PC tried to run the Novas- erating. Always put the delays in very much about a sys- tor programs, every one locked up as a conservative measure, though tem, but these two experiments the computer. Frantic calls to No- they weren't needed. Eliminating demonstrate a valid use for bench- vastor and Always Technology re- those delaysboosted the IN-2000's marks. The All-Star PC won't in all sulted in the discovery that the No- Core test results to almost 1.3M likelihood consistently transfer data vastor files on the hard disk were bytes/see,tying the AHA-1540A. over the SCSI bus at l.3M bytes/sec cormpted; they simply didn't match for every application, no matter their counterparts on the floppy Exonerating the expansion bus what Core's test results say. How- disks. Further testing revealedthat The second experiment took ever, in carefully controlled experi- the IN-2000SCSI host adapterwith place at Cheetah International, ments such as the two described the new BIOS ROM was no longer where, after plugging the original above, the Core benchmark pro- writing data to the disk correctly.

Lost in (memory) space DMA controllershave a tough time working with spond,the first-party DMA controllerwill write pPs that incorporateon-chip memory-management data into the wrong physicaladdresses, which is units, especiallyif the coderunning the DMA con- exactlywhat happenedto the All-Star PC whenit troller doesn'tknow that addresstranslation is oc- usedAdaptec's AHA-1540A. cuning. This scenariooccurs when you use DOS Quarterdeckand Phar Lap SoftwareInc (Cam- extenderprograms, such as Quarterdeck'sQEMM bridge,MA, (617)661-1510) jointly developed,pub- memorymanager, in conjunctionwith expansion lished,and supporta specificationthat allowssoft- cardsthat employfirst-party DMA. QEMMcan map ware suchas a disk BIOSto find out how memory blocksof extendedmemory (located above lM byte hasbeen mapped by the DOS-extensionprogram. in the p,P'saddress space) into unusedaddress This specification,called the VCPI (Virtual Control spacesbelow lM byte, and it can alsoswitch ex- ProgramInterface), provides a functioncall that tendedmemory into the programarea-between 0 suppliesthe logical-to-physicaladdress-mapping in- and 640kbytes-for multitaskingoperations. formation. QEMM handlesmother-board DMA transfersby VCPI hasbecome a de factostandard that several providinga protectedbuffer area, but this technique majorsoftware vendors suppor"t. Adaptec's software won't work for first-party DMA controllersthat are doesn'tsupport VCPI. Instead,it createsa buffer not awareof QEMM. DOSis ignorantof memory for DMA transferswhen they are usedwith DOS managementand providesno way for QEMM to extenders.Invoking this featureofAdaptec's driver tell it that logicalmemory addresses no longermatch carves64k bytes from DOS'salready overcrowded physicaladdresses. Most DOSservices don't need 640kprogram space. Although you canshrink the to know aboutremapped addresses. However, DOS sizeof Adaptec'sDMA buffer (resultingin a speed managesfirst-party DMA controllersand supplies reduction),I judged this solutionto be inadequate them with the destinationaddresses for transfers. for the All-Star PC'sneeds and reluctantlybenched If logicaland physicaladdresses no longercorre- the AHA-1540A. tL4 EDN March29, 1990 Johan Olstenius,the IN-2000's path.on Ft.2gOJt%-in.iticro a..isn.", discovereda logic Ftoppy-Diskttrive slow T^^^ e- ttt.-fiott'uaupterthat wastoo rnc, transfers' :.-::.T9rlqa 7733Tele_ i" ft""af" the fasterSCSI Hllgl lgr r4ontebeilo,cA foJo"ut"tY, the IN-2000emPIoYs vuo4u.(21 3) 727_768d.. gate Xilinx field-programmable q- the r-"^ 6PCAs)- for most of re- Lou"a'tlogic, so the correction STATS: ffi;"J";ly a RoM change'{-sm3ll 4M, the ,n:if;i lLlTformatted): iPnOivf on the IN-2000holds FPGA configuration information' the *fti.ft i.loade=dautomatically by iifi"" parts at powerup' Olstenius ;ffi,,ri.-,,ffiffi:in the ;;i;"d .orn" of the circuitrYin I$fX.?T"'l'Jd.'i?,J81* iitin* chiP to sPeeduP the slow i"ni. ortti. Thii exercise under- SIDES:2 ;;;;;t'th" advantagesof the "soft aPProach hutd*u"." design "*; ploYedon the IN-2000'I Pluggeo in the new conngurationROM' and llifiJffiliffjt,.il:F,ill'#n"J"?'ffifl":#iHilfi afler reinstallingthe tapesoftware' i,"i]ii,,illiit; the ;;.kJ uP the lnformation on harddisks. EDN's All-Star PC incorPorates u *-"*r,a tYPeof storagePeriPheral an N SGSIHost Adapter that Providesarchival storage: til.2000 LpX-SOOOoptical-disk subsystem fto* IVf"*i*um Storage t1c'. ltt3 APX-5000's WORM optlcal-dlsK 500M cartridge stores more than tut.t Jn eachside for a total capac- ity or ,PP"o*imatelY19Pq Pti.": You maY wonder whY the. All-Star tt at- PC has a WORM drive when drive' t*al-g-;th has the ExabYte taPe ttt. ExabYte and Maximum ;'lT-+ils.';+'MoDE:16'bit Bros $ffiIil;ft-'1v:rNr 13H

ffi*;*'lu;tg**rl'iri*tt .:H"F3;s#,1? T"n:,R:'J"IfJ:l;

EDN March29, 1990 surance policy against a hard-disk crash. Although the Maximum Stor- age WORM drive could satisfy the need for backup storage, you would quickly fill up the relatively expen- sive and nonerasable WORM car- tridge if you used it for daily or even weekly . However, the indelible storage and higher speed of the WORM drive provide many benefits to a PC-based(or any other) workstation that are not re- lated to backup storage but to archi- val storage. Archival storage holds files that you wish to savebut don't necessarily need to have immedi- ately at hand. For example, you could use the WORM disk cartridge lo freeze a suite of design and development software in case you ever need to revert to that particular version. Sad stories abound of engineers who neededto revisea design,only Even wlth iust the SCSIand floppy cabling in place, the interior of the AlLStar PCis beconinga rat's negt of wlring. to discover that the particular ver- sions of the CAD and CAE sofbware Storage drives can back up the All- cartridges; the WORM drive pro- tools required for editing the old de- Star PC's two 330M-byte hard-disk vides much faster access to data sign files were long gone. A 1G-byte drives with one cartridge. Four key than the tape cartridge; and the WORM cartridge allows you to save factors differentiate the tape and WORM drive provides indelible several down-level versions of your WORM drives: the tape drive storage. favorite software tools. You can be stores more data per tape cartridge Storage on the tape drive costs confident that those frles cannot be than the WORM drive stores on a less per byte, making tape a better erasedto make room for newer soft- disk cartridge; the tape carbridges alternative for backup storage, ware. The same advantage applies cost much less than the optical-disk which retains information as an in- to different versions of your design What'smissing? The All-Star PC incorporateseight storageperiph- Service(Newton, MA, (617)5584960) provides a erals, but somedevice tlpes are conspicuouslyab- comprehensiveelectronic device catalog called sent. An erasableoptical disk drive wasn't included CAPS(Computer-Aided Product Selection) on CD for two reasons.First, opticaldisks are not standard ROMsand suppliesyou with the CD ROM drives methodsfor data interchangeamong PCs; second, when you subscribeto the CAPS service. the Exabyte and Maximirm Storagedrives provide Also missingfrom the All-Star PC's mass-storage all the archival and backupstorage the All-Star PC menagerieis a network connection-not because needs.Also omittedis a CD ROMdrive, because networkslack merit, rather, becauseof realistic con- the use of suchdrives is still very applicationspe- straints on the project. With only onemachine, there cific. For example,Cahners's Technical Information is simplyno way to test a network card.

116 EDN March29. 1990 Urenf,unner i%-in.Blgid.Diskllrive

(408)438_ Gircterd. eir specifrcationsand Your designs' STATSI Maximum Storage Providestools (unrormatted):3B5M version control as uPdate fi:ft'tt for You LAHA( -tTV ,t- - frles. You can alwaYsretrieve an se"i"'iii ;#Y:T3}ed' 512'byte older version of a file from the ; ;;t :.:.-ulr A_rRAN S F ER WORMdisk cartridge. --"' er r-^ - ^i vP9 -- an external -..'rvr oEFx I tltE. The APX-5000 is , 10.7 unit. TheAll-Star PC usesan exter- nal unit for two reasons.First, it hasno moredrive baYs to accommo- ,'$:#il.t"r%o'Zone bit date a WORMdisk drive. Second, in an environmentwhere engineers BIO: may have an irregular need for the TheWren Runner capabilities of the WORM disk t***rtt'*,**r***M*, drive, the external drive can be i;tt kfl*.;ffi passed-I\{aximum around. You can Plug ? Storagecontroller board into each engineer'sworkstation andshare the drive.That confrgura- muchless than equipping tion costs CarrridseIaFe Sub!$m everyengineering workstation with EI}S200Umm a WORMdrive. MaximumStorage develoPed its own frle'storagesYstem instead of usingthe DOSfile structure,so its E:l?s?,?"dleellei?ifii}f; APX-5000works on a varietY of ?3iil7iii.'q-1-*'i:ti computer sYstems and worksta' tions. The common file format acrossmultiPle comPutersmakes the ability to move the drive from tp""'' evenmore attrac- il?13*x-'.wfgf systemto sYstem tSftG?"tR (aver- tive becausethe APX-5000'sdisk ll$ RArE cartridgebecomes a good medium for data interchangeamong other- wise incomPatiblesYstems. lp-.,'fi$f$s,l??"v..," ESDI The APX-5000drive has an I*1"€h?f"t,."" (EnhancedSmall DeviceInterface) o q,tandard port, soit doesn'twork on the SCSI bus. MaximumStorage suPPlies a proprietarydisk-controller card for ffi lhe drive. The APX-5000, when EDN March29, 1990 ffifrxe:Jif.'sJffi;il,, ffinnW

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o All units meet MIL-T-27E Militarydesignation is TF5R21ZZfor Transformers,TF6RAOZ. for Inductors o Powerof 125Milliwatts at lKHz (Series70000) (.310'Wx .310"Hx .310,,D) Max.distortion 5% o Powerof 400 Milliwatts fi#fi1fi:##il,",,,l[,l'o""J*,:,.:r,#i$ff at lKHz (Series71000) ::,ii:,#r,:,?:r,; (.385',Wx .385"Hx .385"D) Max.distortion 5% o FrequencyResponse +3dB,400H2:250KHZat 1.0 Milliwatt first pluggedinto the All-Star PC, Turbo C and Turbo Pascallibraries o DielectricStrenoth didn't work. The controller had andyou canget that revisedlibrary All unitstested at ZOOVnMS trouble communicatingwith the codefrom Borland. o InsulationResistance drive. However, turning off the With the devicedriver frxed,the Greaterthan 10,000 Megohms at 80486 pP's intenral cache RAM APX-5000 worked flawlessly 300vDc and cured the problem. That clue the All-Star PC's complementof o OperatingTemperature pointed an accusingfinger at the mass-storagedevices -55'C wascomplete. to +105.C APX-5000'sdevice-driver software. That (all unib can be suppliedto classS still left the machinedeaf, requirements,+13OC) In many high-speedPCs, the ex- mute, and blind. il r Terminals pansion-bus'sspeed may cause Conductoris copperclad steel, problems. However, the All-Star References tinned100o/". PC's expansionbus runs at 6 MHz Efectroplatedper MIL-T-I0722 A and l. Wright, Mau4r, "Recent3M- to ASTMCCS 8452. specificallyto avoidsuch problems. 20M-byte,3%-in. floppy-disk drives suit o ThermalShock Barry Bremsteller at Maximum mainstreamuses," EDN, October22, 25 cycles,method 107D, MIL-STD- Storage discoveredthe problem's 1988,pg 103. 202E,test conditionA-1 cause. The driver routines that 2. Wright, Maury, "\Minchesterdisk drives,"EDN,May monitoredthe proper operationof 25, 1989,pgl2Z. PICOmanufactures complete lines ot 3. lVright, Maury, "Helical-scan Transformers,lnductots and DC-DC Converterc the controllercard were timing out drives store gigabyteson trny tape ear- before the hardware had time to tridges,".EDN,Decembet 22, lg8i8, executeits commands.The culprit pg 129. provedto be the delay function in 4. Leibson,Steven H, "Optical-disk BorlandInternational's (Scotts drivestarget standard5%-in. sites," Val- EDN, December25, pg ley, (408) 1986, 42. CA, 439-1800)Turbo C 5. Terry, Chris, "Rewritable optical- functionlibrary. The delay routine disk drives, optical units provide mass is self- calibrating over a range of storage,"EDN,May ll, 1989,pg 59. Electronics,Inc. pP speeds, 453 N. MacQuesten Plsy. Ml. Vernon, N.Y. 105SA but the 80486simply CattTott Frce 8OO.43l.l 064 burst past the limits of the self-cali- Article Intercst Quotient rNNEw YoRK cALr 914.699.5514 bration algorithm. The company (Circle One) has fixed the delay function in its High 512 Medium 5l3Iow 514 clRcLE NO.59 EDN March29, f990