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4. Prosbash diskoy

Gia na diabasete h na gracete kati apo to disko, prepei na deijoyme th 8esh sto disko, dinontas gia paradeigma ton tomea h thn enothta. An o diskos einai SCSI, tote o ari8mos toy tomea phgainei katey8eian sthn entolh SCSI kai o diskos thn katalabainei. An o diskos einai IDE xrhsimopoiwntas LBA, isxuei to idio. Alla an o diskos einai palios RLL h MFM h IDE ths pro-LBA epoxhs, tote o diskos perimenei ena triplo ari8mo (kulindro, kefalh, tomea) gia na katadeijei to shmeio.

H antistoixia metaju grammikhs dieu8ynshs kai ths 3D shmeiografias einai: gia ena disko me C kylindroys, H kefales kai S tomeis/ixnos h 8esh (c,h,s) se 3D h CHS einai h idia 8esh me c*H*S + h*S + (s-1) se grammikh h LBA. (To meion ena einai epeidh oi tomeis arxizoyn kata paradosh apo to 1, oxi to 0 opws sto 3D).

Kata synepeia, gia na prosbash se enan polu palioo mh-SCSI disko, prepei na jeroyme thn gewmetria, dhladh, tis times C, H kai S.

4.1 Prosbash toy BIOS kai to orio twn 1024 kylindrwn

To Linux de xrhsimopoiei to BIOS, alla alla systhmata to xrhsimopoioun. To BIOS, poy prouparxei toy LBA, prosferei tis roytines diskoy INT13 poy dexontai (c,h,s) parametroys. (Akribestera: to AH dialegei th leitoyrgia poy 8a ektelestei, to CH einai ta katw 8 bits toy onomatos toy kylindroys, to CL exei sta bits 7-6 ta anw dyo bits toy ari8mou toy kylindroy kai sta bits 5-0 ton ari8mo toy tomea, DH einai o ari8mos ths kefalhs, kai DL einai o ari8mos toy diskoy (80h h 81h). Ayto ejhgei merika th diatajh toy pinaka katatmhsewn.)

Etsi, exoyme to CHS kwdikopoihmeno se 3 bytes, me 10 bits gia to onoma toy kylindroy , 8 bits gia thn kefalh kai 6 bits gia ton ari8mo ixnoys tomea (1-63). Ejypakouetai oti oi kulindroi mporei na einai apo 0 ews 1023 kai de mporoun na ari8mh8oun panw apo 1024 kulindroi apo to BIOS.

To DOS kai ta Windows den allajan otan IDE diskoi me yposthrijh LBA emfanisthkan, opote to DOS kai ta Windows synexisa na xreiazontai gewmetria diskoy, akoma ki otan ayto de xreiazotan apo to I/O toy diskoy, alla mono gia na epikoinwnoun me to BIOS. Ayto jana shmainei oti to Linux xreiazetai th gewmetria opoy epikoinwnia me to BIOS h me alla leitoyrgika apaiteitai, akoma kai se monternoys diskoys.

Ayth h katastash krathse gia tessera xronia peripoy kai meta emfanisthkan sthn agora diskoi poy de mporousan na klh8oun me tis synarthseis INT13 (ka8oti ta 10+8+6=24 bits gia (c,h,s) den mporoun na ari8mhsoyn panw apo 8.5 GB) kai mia nea diasundesh me to BIOS sxediasthke: oi apokaloumenes Extended INT13 synarthseis, opoy to DS:SI deixnei sto 16-byte Disk Address Packet poy perilambanei enan 8mpito ari8mo enothtwn.

Polu arga o kosmos ths Microsoft kineitai pros th xrhsh aytwn twn Extended INT13 synarthsewn. Mallon se merika xronia apo shmera, kanena monterno susthma de 8a xreiazetai th gewmetria toy diskoy.

4.2 Istoria toy BIOS kai twn oriwn toy IDE

ATA Specification (gia IDE diskoys) - to orio twn 137 GB

To polu 65536 kulindroi (ari8mhmenoi 0-65535), 16 kefales (ari8mhmenes 0-15), 255 tomeis/ixnos (ari8mhmenoi 1-255) gia mia megisth xwrhtikothta 267386880 tomewn (512 bytes o ka8enas), dhladh, 136902082560 bytes (137 GB). Ayto akoma den einai problhma (to 1999), alla 8a einai se merika xronia apo shmera.

BIOS Int 13 - to orio twn 8.5 GB

To polu 1024 kulindroi (0-1023), 256 kefales (0-255), 63 tomeis/ixnos (1-63) gia megisth xwrhtikothta 8455716864 bytes (8.5 GB). Aytos einai enas arketa sobaros periorismos shmera. Shmainei oti to DOS de mporei na xrhsimopoihsei toys neoys megaloys diskoys.

To orio twn 528 MB

An oi idies times c,h,s xrhsimopoiountai gia to BIOS Int 13 call kai gia to I/O toy IDE diskoy, kai oi dyo periorismoi syndyazontai kai mporoume na xrhsimopoihsoyme to polu 1024 kylindroys, 16 kefales kai 63 tomeis/ixnos gia megisth telikh xwrhtikothta 528482304 bytes (528MB), to perifhmo orio twn 504 MiB gia DOS me palio BIOS. Ayto egine problhma to 1993 kai efeyre8hkan polla texnasmata, kai se yliko (LBA), kai firmware (metafrazontas to BIOS) kai se software (diaxeiristes diskwn). H ennoia ths 'metafrashs' efeyre8hke (1994): to BIOS mporouse na xrhsimopoiei mia gewmetria otan epikoinwnouse me to disko kai allh, ceydh, gewmetria otan milouse sto DOS, kai na metafrasei metaju toys.

To orio twn 2.1 GB (Aprilios 1996)

Merika palia BIOS xrhsimopoioun mono 12 bits gia to pedio sth CMOS RAM poy dinei ton ari8mo twn kylindrwn. Kata synepeia, o ari8mos aytos mporei na einai to polu 4095, kai mono 4095*16*63*512=2113413120 bytes einai prosbasima. To na yparxei megaluteros diskos exei ws apotelesma to kremasma kata thn ekkinhsh. Ayto ekane diskoys me gewmetria 4092/16/63 arketa dhmofilhs. Akoma kai shmera yparxoyn megaloi diskoi poy erxontai me diakopth gia emfanizontai ws 4092/16/63. Deite kai to over2gb.htm.

To orio twn 3.2 GB

Yphrxe ena megalo bug sto Phoenix 4.03 kai 4.04 BIOS poy ta ekane na kollane sto CMOS setup gia diskoys megaluteroys twn 3227MB. Deite to over3gb.htm.

To orio twn 4.2 GB (Febroyarios 1997)

H aplh metafrash toy BIOS (ECHS=Extended CHS, merikes fores legetai kai `Large disk support' h apla `Large') leitoyrgei me ton synexh diplasiasmo toy ari8mou twn kefalwn kai ton ypodiplasiasmo toy ari8mou twn kylindrwn poy deixnontai sto DOS, mexri oi kulindroi na einai to polu 1024. To DOS kai ta Windows 95 de mporoun na diaxeiristoun 256 kefales, kai sthn periptwsh poy o diskos anaferei 16 kefales, ayto shmainei oti o aplos aytos mhxanismos mporei na doylecei gia mexri 8192*16*63*512=4227858432 bytes (me ceydh gewmetria me 1024 kylindroys, 128 kefales, 63 tomeis/ixnos). Shmeiwste oti to ECHS den allazei ton ari8mo twn tomewn ana ixnos, opote an den einai 63, to orio 8a einai akoma xamhlotero. Deite to over4gb.htm.

To orio twn 7.9 GB

Ligo pio ejypna BIOS apofeugoyn ayto to problhma me th ru8mish prwta toy ari8mou twn kefalwn se 15 (`revised ECHS'), wste h ceydhs gewmetria na diathreitai me 240 kefales, arketo gia 1024*240*63*512=7927234560 bytes.

To orio twn 8.4 GB

Teleiwnontas, an to BIOS kanei o,ti mporei gia mia epityxh metafrash, xrhsimopoiei 255 kefales me 63 tomeis/ixnos (`assisted LBA' or just `LBA') kai ftanei ta 1024*255*63*512=8422686720 bytes, ligo mikrotero apo to prohgoumeno orio twn 8.5 GB, efoson gewmetries me 256 kefales prepei na apofeugontai. (H metafrash 8a xrhsimopoihsei gia ton ari8mo kefalwn ton ari8mo H apo thn akoloy8ia 16, 32, 64, 128, 255 gia thn opoia h synolikh xwrhtikothta ftanei sta 1024*H*63*512, kai meta ypologizei ton ari8mo twn kylindrwn C ws thn xwrhtikothta diairoumenh me (H*63*512).)

The 33.8 GB limit (August 1999)

To epomeno empodio erxetai me mege8h anw twn 33.8 GB. To problhma einai oti me 16 kefales kai 63tomeis/ixnos ayto antistoixei se ari8mo kylindrwn panw apo 65535, poy de xwraei se short ari8mo. Ta perissotera BIOS shmera de mporoun na xeiristoun tetoioys diskoys. (Deite Asus upgrades gia nees ekdoseis poy doyleuoyn.) Pyrhnes palaioteroi twn 2.2.14 / 2.3.21 xreiazontai patch. Deite IDE problhmata me 34+ GB diskoys parakatw.

Gia peraiterw syzhthsh aytou toy 8ematos deite Breaking the Barriers kai, gia perissoteres leptomereies, IDE Hard Drive Capacity Barriers.

Diskoi megaluteroi twn 8.4 GB anaferoyn th gewmetria toys ws 16383/16/63. Ayto shmainei oti h 'gewmetria' einai aneparkhs kai oti h synolikh xwrhtikothta de mporei na ypologistei apo th gewmetria.


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