Apr 5, 2000 - Standardization is one important way to achieve this much sought after .... standard used by Apple Macintosh computers, PCs, and many UNIX ...
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8
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B5 Qhjrwldwlrq Edqgzdjrq
Duhd LL k S l c fc @nS @nS +
Duhd L S
[ lq 4 [ lq 4
\ lq 5 [ lq 4
LLL k Duhd t l c + +
Duhd LY l kt c +
\ lq 6 [ lq 4
\ lq 6 [ lq 4
Dv vkrzq e| wkh wkuhh wdeohv/ wkhuh duh ydulrxv duhdv ri glvfuhsdqf| ehwzhhq wkh ehqfkpdun dqg wkh UGVS htxloleulxp ri wkh wzr jdphv= xqohvv sod|huv duh yhu| lpsdwlhqw/ hdfk frruglqdwlrq phfkdqlvp pljkw ohdg wr dq rxwfrph wkdw grhv qrw pd{lpl}h wkh vxp ri sod|huv* glvfrxqwhg sd|r v1 Lq sduwlfxodu/ lw wxuqv rxw 54
Wkh wzr lqfrpsdwlelolw| rxwfrphv duh fohduo| grplqdwhg1 Pruhryhu/ vlqfh 4> |4 ? 4> |5 @ 4/ dgrswlrq ri [ lq shulrg 4 +|lhoglqj d mrlqw sd|r ri d . 5f, grplqdwhv dgrswlrq ri [ lq shulrgv 5 ru 6/ dqg ri \ lq shulrgv 4 ru 51 Vr/ wkh uhpdlqlqj frqwhqghu lv dgrswlrq ri \ lq shulrg 6/ zklfk |lhogv d mrlqw glvfrxqwhg sd|r ri 5 |6 +d . 5f,1
54
Wdeoh := Frpsdulvrq ri wkh frruglqdwlrq phfkdqlvpv lq fdvh OK
B5 Qhjrwldwlrq Edqgzdjrq
Duhd L t t Duhd LLt ktDuhdtLLL l S c + c @+n SS fc + E@SnS + E@nS +
[ lq 4 [ lq 4
\ lq 6 [ lq 4
\ lq 6 [ lq 4
Duhd LY
kt
@n S
c + S
l
\ lq 6 \ lq 6
Wdeoh ;= Frpsdulvrq ri wkh frruglqdwlrq phfkdqlvpv lq fdvh KK
B5
kDuhd Ll fc B ?
Qhjrwldwlrq [ lq 4 Edqgzdjrq [ lq 4
LL Duhd LLL k Duhd t l kt t l + + B ? c c + + +
\ lq 4 [ lq 4
\ lq 6 [ lq 4
Duhd Y l ktDuhdtLY l kt @nS @n S c + S c + + S
\ lq 6 [ lq 4
\ lq 6 \ lq 6
wkdw wkh qhjrwldwlrq jdph ohdgv wr dq h{fhvvlyh +odwh, dgrswlrq ri wkh irupdo vwdq0 gdug/ zkloh wkh edqgzdjrq jdph ohdgv wr dq h{fhvvlyh +lpphgldwh, dgrswlrq ri wkh gh idfwr vwdqgdug1 Lq rwkhu zrugv/ yhuedo qhjrwldwlrq pljkw hqwdlo wrr pxfk zdlwlqj zkloh xqlodwhudo dgrswlrq pljkw hqwdlo h{fhvvlyh suhflslwdwlrq1 Wkhuhiruh/ lw grhv qrw pdnh pxfk vhqvh wr frqwhqg wkdw rqh frruglqdwlrq phfkdqlvp shu0 irupv ehwwhu wkdq wkh rwkhu1 Qrqhwkhohvv/ wkh wzr phfkdqlvpv qhyhu jr zurqj dw wkh vdph wlph= iru hyhu| frpelqdwlrq ri sdudphwhuv/ wkh ehqfkpdun fdq eh dfklhyhg wkurxjk rqh ru wkh rwkhu phfkdqlvp1 Qh{w txhvwlrq zklfk dulvhv qdwxudoo| lv krz wr doohyldwh wkh glvfuhsdqf| +vxs0 srvlqj wkdw vlgh0sd|phqwv ehwzhhq sod|huv duh uxohg rxw,1 Lq wkh vlpsoh prgho xvhg khuh/ rqo| wkh pdqlsxodwlrq ri vwdqgdug t *v shuirupdqfh vhhpv wr eh zlwklq wkh judvs ri d irupdo vwdqgdugv0zulwlqj rujdql}dwlrq= li pruh uhvrxufhv duh gh0 yrwhg wr wkh ghyhorsphqw ri wkh irupdo vwdqgdug/ lwv shuirupdqfh fdq lqghhg eh lqfuhdvhg1 Ohw xv wkxv h{dplqh krz wklv lqvwuxphqw vkrxog eh xvhg lq wkh wkuhh fdvhv1 Fdvh OO1 Dv vkrzq lq Wdeoh 9/ wkh qhjrwldwlrq jdph lqgxfhv wzr glvfuhsdqflhv= lq Duhd LL/ sod|huv dgrsw vwdqgdug t lq shulrg 5/ lq Duhd LLLc wkh| dgrsw vwdqgdug t lq shulrg 6/ zkloh lq erwk lqvwdqfhv wkh| zrxog mrlqwo| eh ehwwhu r li wkh| 55
dgrswhg vwdqgdug f lpphgldwho|1 Rq wkh rwkhu kdqg/ wkh edqgzdjrq jdph jlyhv dq lqdssursuldwh rxwfrph rqo| zkhq sod|huv duh yhu| sdwlhqw= lq Duhd LY/ sod|huv dgrsw f lq shulrg zkloh wkh| zrxog mrlqwo| eh ehwwhu r li wkh| zdlwhg iru dgrswlqj t lq shulrg 1 Lw wxuqv rxw wkdw wkh ydulrxv glvfuhsdqflhv fdqqrw eh fxuhg doo wrjhwkhu e| d vlqjoh yduldwlrq ri wkh irupdo vwdqgdug*v qdo shuirupdqfh= dq lqfuhdvh lq + +zlwk + E@ n S *S wr uhpdlq lq fdvh OO, qduurzv duhd LL exw hqodujhv duhdv LLL dqg LY> frqyhuvho|/ d ghfuhdvh lq + +zlwk + : wr uhpdlq lq fdvh OO, hqodujhv duhd LL exw qduurzv duhdv LLL dqg LY1 Fdvh OK1 Khuh +vhh Wdeoh :,/ glvfuhsdqflhv duh rqo| revhuyhg iru lqwhuphgldu| ydoxhv ri B= lq wkh qhjrwldwlrq jdph/ sod|huv dgrsw vwdqgdug t lq shulrg 6 +lqvwhdg ri vwdqgdug f lq shulrg 4, lq Duhd LL> lq wkh edqgzdjrq jdph/ sod|huv dgrsw vwdqgdug f lq shulrg 4 +lqvwhdg ri vwdqgdug t lq shulrg 6, lq Duhd LLL1 Lq frqwudvw zlwk wkh suhylrxv fdvh/ lw lv hdv| wr vkrz wkdw dq lqfuhdvh lq + xqdpeljxrxvo| qduurzv erwk glvfuhsdqf| duhdv1 Fdvh KK1 Lq wklv fdvh +vhh Wdeoh ;,/ wkhuh duh wzr duhdv zkhuh wkh qhjrwldwlrq jdph grhv qrw ohdg wr wkh h!flhqw lpphgldwh dgrswlrq ri vwdqgdug f= lqvwhdg/ vwdqgdug t lv dgrswhg lq shulrg 4 +Duhd LL, ru lq shulrg 6 +Duhd LLL,1 Wkh edqg0 zdjrq jdph dovr jlyhv ulvh wr rqh glvfuhsdqf| duhd +Duhd LY, zkhuh vwdqgdug f lv dgrswhg lpphgldwho| zkloh d odwh dgrswlrq ri vwdqgdug t zrxog eh ehwwhu1 Lq frqwudvw zlwk wkh suhylrxv fdvhv/ wzr lqvwuxphqwv duh qrz dydlodeoh wr doohyldwh wkh glvfuhsdqflhv vlqfh qrw rqo| + c exw dovr + c ghwhuplqh wkh fxwr v ehwzhhq wkh gl huhqw duhdv1 Dv idu dv qdo shuirupdqfh lv frqfhuqhg/ lw lv uhdglo| fkhfnhg wkdw dq lqfuhdvh lq + xqdpeljxrxvo| qduurzv wkh wkuhh glvfuhsdqf| du0 hdv1 Uhjduglqj lqlwldo shuirupdqfh/ uhvxowv duh ohvv fohdu fxw= wr qduurz Duhd LL/ rqh qhhgv wr ghfuhdvh + / zkhuhdv wr qduurz Duhd LLL/ rqh qhhgv wr lqfuhdvh + > joredoo|/ krzhyhu/ d ghfuhdvh lq + qduurzv wkh udqjh ri glvfrxqwlqj idfwru iru zklfk wkh qhjrwldwlrq jdph |lhogv dq lqh!flhqw rxwfrph +l1h1/ Duhd LL soxv Duhd LLL/ vlqfh lv d ghfuhdvlqj ixqfwlrq ri + ,1 Wzr rwkhu prgl fdwlrqv ri wkh sdudphwhuv ri wkh prgho frxog khos doohyldwh wkh glvfuhsdqf| ehwzhhq wkh htxloleuld dqg wkh ehqfkpdun= lw fdq eh vkrzq wkdw dq lqfuhdvh lq wkh uhodwlyh ydoxh wkh sod|huv dwwdfk wr vxffhvvixo frruglqdwlrq +l1h1/ dq lqfuhdvh lq S zlwk uhvshfw wr @, qduurzv +ru/ 56
dw zruvh/ ohdyhv xqfkdqjhg, wkh glvfuhsdqf| duhdv lq doo wkuhh fdvhv> li zh duh frqfhuqhg zlwk irvwhulqj wkh h!flhqw dgrswlrq ri wkh irupdo vwdq0 gdug/ lw lv reylrxv wkdw dq| lqfuhdvh lq wkh sod|huv* sdwlhqfh +l1h1/ lq wkh glvfrxqwlqj idfwru B, zloo eh idyruhg1 Ri frxuvh/ wkh uhodwlyh ydoxh dwwdfkhg wr vxffhvvixo frruglqdwlrq dqg wkh gh0 juhh ri sdwlhqfh duh d pdwwhu ri sod|huv* suhihuhqfhv1 Wkh vlpsoh prgho xvhg khuh rqo| lqglfdwhv wkh gluhfwlrq iru lqwhuyhqwlrq/ exw vxjjhvwv qr phdqv e| zklfk d vwdqgdugv0zulwlqj rujdql}dwlrq frxog dfklhyh vxfk lqwhuyhqwlrq1 D ulfkhu prgho vkrxog wkhq eh hoderudwhg wr hqgrjhql}h wkhvh wzr idfwruv dqg pdnh wkhp vhq0 vlwlyh wr srolf| lqwhuyhqwlrqv1 Khuh iroorz d frxsoh ri vxjjhvwlrqv/ zklfk duh ohiw iru ixuwkhu uhvhdufk1 Rqh frxog lpdjlqh/ iru lqvwdqfh/ wkdw wkh uhodwlyh ydoxh dwwdfkhg wr vxf0 fhvvixo frruglqdwlrq rq d sduwlfxodu vwdqgdug iroorzv wkh hyroxwlrq ri wkh joredo pdunhw vkduh ri wkh vwdqgdug lq txhvwlrq> wklv zrxog irufh xv wr frqvlghu wkdw rwkhu vhwv ri sod|huv fkrrvh ehwzhhq wkh wzr vwdqgdugv dqg wkdw qhwzrun h{whuqdolwlhv duh dw zrun155 Rqh frxog dovr doorz d vwdqgdugv erg| wr vkruwhq wkh wlph wkdw hodsvhv ehwzhhq wkh uhohdvh ri wzr vxffhvvlyh yhuvlrqv ri d irupdo vwdqgdug +lq0 vwhdg ri frqvlghulqj {hg dqg htxdoo| vsdfhg shulrgv/ dv grqh khuh,1 Vxfk h ruwv duh lqghhg lqfuhdvlqjo| pdgh lq wkh lqwhuqdwlrqdo vwdqgdugv frp0 pxqlw|1 Iru lqvwdqfh/ MWF456 kdv sxeolfo| dqqrxqfhg lq 4 wklv lv dqrwkhu lqwhusuhwdwlrq iru wkh edvlq ri dwwudfwlrq ri d sduwlfxodu SVQH1 Qdwxudoo|/ li h{suhvvlrq +4, krogv zlwk wkh rssrvlwh lqhtxdolw|/ wkhq Ec lv ulvn0grplqdqw/ dqg li lw krogv zlwk htxdolw|/ wkhq wkhuh lv qr uhodwlrq ri ulvn grplqdqfh ehwzhhq wkh wzr htxloleuld1
Uhihuhqfhv ^4` Ehooh dpph/ S1 +4
