[cctalk] IBM 350 disk and 305 drum [WAS:RE: Re: Drum memory on pdp11's? Wikipedia thinks so....]

The IBM 350 disk storage (RAMAC) has 5 million 6-bit characters or 3.75 MB; the actual recorded characters were 8-bits in length including a parity bit and a stop bit for each recorded 6-bit character It was announced as part of the IBM 305 RAMAC system which had drum memory which as far as I can tell had 24 tracks of 100 6-bit characters = 14,400 bits or 1.8 kB Source: http://bitsavers.trailing-edge.com/pdf/ibm/305_ramac/22-6264-1_305_RAMAC_Ma… pgs 17 &18 If anyone has a better number please post it 😊 Tom -----Original Message----- From: Mike Katz &lt;bitwiz(a)12bitsbest.com&gt; Sent: Monday, April 15, 2024 9:33 AM To: General Discussion: On-Topic and Off-Topic Posts &lt;cctalk(a)classiccmp.org&gt; Cc: Douglas Taylor &lt;dj.taylor4(a)comcast.net&gt; Subject: [cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so.... There was drum storage for the early PDP-8 the "Straight 8", PDP-9 and PDP-10. Each drum stored 32,768 words. Up to 8 of them could be connected for a total storage of 262,144 words of storage. IBM made a 5BM drum storage unit that was the side of a small refrigerator: The RAMAC's disk storage unit, the IBM 350, weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. It stored approximately 5MB of data: *five million 8-bit characters on fifty 24-inch-diameter disks*, a form of drum memory. <snip>