Neu ban chiu kho de y thi co the
thay rang tat ca cac cong nghe hien nay deu co xu huong chuyen dich tu giao tiep
song song (parallel) sang chuoi (serial). Chuan IDE moi danh cho o cung cung la
Serial (Serial ATA - SATA). Roi den bus PCI cung da chuyen sang dang chuoi voi
chuan PCI Express. Con giao dien SCSI cung dang chuyen sang chuoi.
Diem khac biet duy nhat giua giao
tiep chuoi voi giao tiep song song la chuan nay chi truyen mot bit trong mot
khoang thoi gian, trong khi giao tiep song song truyen nhieu bit trong mot
khoang thoi gian. Su khac biet nay khien cho giao tiep song song thuong nhanh
hon giao tiep chuoi.
Tuy nhien, khong phai thuc te
tren deu dung trong moi truong hop. Giao tiep chuoi cung co the nhanh hon giao
tiep song song neu cac bit duoc chuyen di voi toc do nhanh hon. Chang han, cong
SATA co the dat toc do truyen du lieu len toi 150Mbps, trong khi cong IDE truyen
thong chi dung o muc 133Mbps.
Co mot vai ly do de chuyen thiet
bi tu giao tiep song song sang giao tiep chuoi. Trong giao tiep song song, do
nhieu bit duoc chuyen di trong mot khoang thoi gian nen moi bit can co mot day
dan. Chang han, trong mot giao tiep 32 bit se can 32 day dan de truyen du lieu,
do la chua ke den cac day danh cho tin hieu. So luong bit duoc chuyen di moi lan
cang cao thi cang can nhieu day dan, gay kho khan cho qua trinh san xuat cap va
chi phi lap dat. Trong giao tiep chuoi, chi can hai day dan, vi the nen qua
trinh giao tiep giua hai thiet bi se don gian hon rat nhieu.
 Ti le truyen du lieu cang cao thi
qua trinh can thiep dien tu cang de nay sinh. Moi day dan deu co the tro thanh
mot anten, thu nhieu tieng on tu moi truong ben ngoai, lam anh huong toi qua
trinh truyen du lieu. Trong giao tiep song song, do nhieu day dan duoc su dung
nen qua trinh can thiep dien tu rat nghiem trong. Con trong giao tiep chuoi thi
nguoc lai, do chi co hai day dan tham gia vao qua trinh truyen du lieu nen van
de de giai quyet hon rat nhieu, va do vay co the dam bao do an toan cho day dan.
Van con mot van de nho can de cap
toi o day. Do la ngay ca khi chung ta noi trong giao tiep song song, tat ca cac
bit deu duoc truyen cung mot thoi diem, nhung dieu do khong co nghia cac bit deu
toi dau nhan (receiver) vao cung mot thoi diem. Neu trong mot thiet bi co cong
suat nho thi dieu nay khong quan trong lam, nhung neu do la cac thiet bi toc do
cao thi su khac biet ve thoi gian tiep nhan cac bit se khien cho thiet bi lang
phi thoi gian (vi phai cho doi tat ca cac bit den). Va dieu nay co the anh huong
nghiem trong toi hieu suat hoat dong cua thiet bi do qua trinh truyen du lieu
chi dien ra trong nhung khoang thoi gian rat ngan ngui.
Them mot su khac biet khac nua la
giao tiep song song la qua trinh “nua hai chieu” (half-duplex), con giao tiep
chuoi la qua trinh “hai chieu” (full-duplex). Mot cach cu the hon: trong giao
tiep song song, chi co duy nhat mot duong dan de truyen du lieu giua bo truyen
va bo nhan. Do chi co mot duong duy nhat nen khong the dong thoi cung truyen va
cung nhan du lieu o cung mot thoi diem. Con trong giao tiep chuoi, do chi su
dung hai day dan nen cac nha san xuat thuong tang cuong them hai day dan nua
(tong cong la 4 day). Hai day dan cho truyen du lieu va hai day dan con lai de
nhan du lieu. Noi cach khac, trong giao tiep chuoi se co hai duong song song,
mot danh cho truyen, con mot danh cho nhan du lieu. Kha nang nay giup qua trinh
truyen va nhan du lieu dien ra dong thoi.
Su khac biet ve kien truc tren giup giao tiep chuoi co the truyen du lieu cao
gap hai lan so voi giao tiep song song.
Article source http://w4rum.com/592.t
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