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IBM's 350 disk storage unit, announced with the IBM 305 RAMAC computer on 14 September 1956, was the first commercial hard disk drive. It held 5 million characters (letters or digits), about 3.75 megabytes by today's measure, and weighed about a ton.

IBM, 1956

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The story behind the card

RAMAC stood for Random Access Method of Accounting and Control. Random access, the ability to go straight to any record, was the whole point. Business records were usually kept on punched cards or magnetic tape, which had to be worked through in order, while the disk drive could reach any record in under a second, about 600 milliseconds on average. Inside, a stack of 52 disks, each 61 centimetres across, spun at 1,200 revolutions a minute, and an arm moved between them to read and write. The whole RAMAC system could be leased for 3,200 US dollars a month. The drive was developed at IBM's laboratory in San Jose, California, and the first production units shipped in 1957. A phone today stores tens of thousands of times as much.

Türkçe oku
İlk ticari sabit disk sürücüsü IBM'in 350 disk birimiydi; şirket onu 14 Eylül 1956'da IBM 305 RAMAC bilgisayarıyla birlikte duyurdu. Sürücü 5 milyon karakter (harf ya da rakam), yani bugünkü ölçüyle yaklaşık 3,75 megabayt veri saklıyordu ve yaklaşık bir ton ağırlığındaydı.

RAMAC, İngilizcede “muhasebe ve denetim için rastgele erişim yöntemi” anlamına gelen adın kısaltmasıydı. Asıl yenilik de rastgele erişimdi, yani istenen kayda doğrudan gidebilmek. Şirket kayıtları genellikle delikli kartlarda ya da manyetik bantlarda tutuluyordu ve bunların baştan sona sırayla taranması gerekiyordu. Disk sürücüsü ise herhangi bir kayda bir saniyeden kısa sürede, ortalama 600 milisaniyede ulaşabiliyordu. İçinde her biri 61 santimetre çapında 52 disk dakikada 1.200 devirle dönüyor, aralarında gidip gelen bir kol veriyi okuyup yazıyordu. Bütün RAMAC sistemi ayda 3.200 dolara kiralanabiliyordu. Sürücü, IBM'in Kaliforniya'nın San Jose kentindeki laboratuvarında geliştirildi; seri üretilen ilk örnekler 1957'de teslim edildi. Bugün bir telefon bunun on binlerce katını saklayabiliyor.

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Background reading: IBM 305 RAMAC
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