Ch4 RAM - I RAM II Historical/Conceptual A...

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I. RAM II. Historical/Conceptual A. RAM – (Random-Access Memory) i. program copied frm mass storage to RAM then ran B. not in use, programs held in mass storage (harddrive, floppy-disk, CD-ROM disk) C. “random access” - any part of memory be accessed wit equal ease III. DRAM (Dynamic random-access memory) A. stores individual 1's and 0's using microscopic capacitors and transistors B. # of chips soldered onto a card of some type IV. Organizing DRAM A. standard RAM used in all computers i. low cost, high speed, capability to contain a lot of data on small package B. need RAM to store data in 8-bit chunks for 8088 processor (8-bit external data bus) C. CPU needs memory to store programs and data in 8-bit(1-byte) chunks i. byte-wide memory (memory in PC) D. two values (units of bits) – combined: get size of DRAM i. depth (also called height) ii. width iii. depth K(bit) x width (bit) E. impossible to tell size of DRAM by looking at it i. can be different inside but look the same ii. only can tell by reading info printed on chip (cant decipher info) V. A Historical Look A. original IBM PC – 640KB DRAM (most) B. “Everything old is new again.” C. 1-bit wide (old days) D. organized with the memory controller chip E. made 1-bit wide DRAMs to look like 8-bit wide DRAM i. eight 1-bit wide chips in a row on motherboard ii. wire up row of DRAM to MCC F. row of chips i. add up to eight bits ii. chip had to be same depth VI. Multiple Rows A. days of 8088 processor i. biggest DRAM chip – 256K x 1 ii. add more rows to get more than 256K of RAM B. adding more rows – needed improved MCC – new chipsets
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