On Sun, 8 Sep 2013 09:58:29 -0700, Jon Perryman wrote: >WOW. How did it use drum as main memmory? Did it have like 1K of real memory >and have hardware to move from drum upon address resolution? Or is drum a >similar architecture to ram? > Nope. None of the above. The drum was "real". From:
http://en.wikipedia.org/wiki/IBM_650#Hardware The rotating drum memory provided 2,000 signed 10-digit words of memory ..., which is approximately 8.5 KB in today's units. ... A word could not be accessed until its location on the drum surface passed under the read/write heads during rotation (rotating at 12,500 rpm, the non-optimized average access time was 2.5 ms). ... That's ms, not μs. Programs could be optimized by placing instructions around the drum based on the expected execution time of the previous instruction. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN