|International Business Machines Corporation introduced a new version of computer in the September of 1956--IBM 305 RAMAC (Random Access Memory Accounting) system. It was certainly one of the last vacuum tube systems created in International Business Machines, but... it introduced disk storage technologies to the planet and is the starting point of each mechanical disk drive to date--IBM 350 Disk Storage, therefore it became a marketplace hit and more than 1000 305s were built before manufacturing ended in 1961.|
The 350 Disk Storage Device consisted of the magnetic disk memory device using its entry mechanism, the pneumatic and digital controls for the entry apparatus, and a little air compressor. manufactured with covers, it was 170 cm high, 150 cm long and 72 cm deep. It had been configured with 50 24-inch magnetic disks comprising of 50000 sectors, all of which held 100 alphanumeric characters, to get a total capacity of 5 million figures. Overall the RAMAC has around about 5MB of storage space, it may seem extremely small but in the 50's that capacity of storage was considered extremely big.
The hard drives disks spun around at 1200 rpm, tracks (20 per inch) were recorded at up to 100 bits per inch. The rendition of a "seek" instruction placed a read & write head to the track that contained the desired sector and picked the sector to get an after read or write operation. Seek time in general was around 600 milliseconds. The hard drive system costs some people $10000.
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