Early Memories Early Memories Memory Prof. Stephen A. Edwards
[email protected] NCTU, Summer 2005 Williams Tube CRT-based random access memory, 1946. Used on the Manchester Mark I. 2048 bits. Mercury acoustic delay line. Used in the EDASC, 1947. 32 × 17 bits Memory – p. 1/23 Memory – p. 2/23 Memory – p. 3/23 Early Memories Early Memories Modern Memory Choices Family Programmed Persistence Mask ROM at fabrication 1 PROM once 1 EPROM 1000s, UV 10 years FLASH 1000s, block 10 years EEPROM 1000s, byte 10 years Magnetic core memory, 1952. IBM. NVRAM 1 5 years Magnetic drum memory. 1950s & 60s. SRAM 1 while powered Secondary storage. DRAM 1 64 ms Memory – p. 4/23 Memory – p. 5/23 Memory – p. 6/23 ROMs EPROMs EEPROM and FLASH Slow write Fowler- Oxide Nordheim Tunneling floating gate Word Line EEPROM: bit at a time Drain (bit line) FLASH: block Source Channel at a time Source: SST Memory – p. 7/23 Memory – p. 8/23 Memory – p. 9/23 Static RAM Cell Standard SRAM: 6264 Standard SRAM: 6264 19±15,13±11 Word D[7:0] ¡£¢ ¤ ¡£¢ ¤ 10±2,25±23,21 8K × 8 Addr[12:0] CS1 ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ 22 Can be very fast: 1CY 626 4 OE ¤ ¡£¢ ¤ ¡£¢ 27 Cypress sells a 55ns WE CS2 20 version ¢ ¢ ¢ ¢ ¢ ¢ ¢ CS1 PRELIMINARY 26 Simple, asynchronous ¡£¢ ¤ CY6264 CS2 WE interface ¢ ¢ 8K x 8 Static RAM ¡£¢ ¤ Bit Bit OE Features over 70% when deselected. The CY6264 is packaged in a ¢ 450-mil (300-mil body) SOIC. • 55, 70 ns access times An active LOW write enable signal (WE) controls the writ- ¥ ¥¦ § § § § § § §¨ ¥ ¥ ¥¦ § § § ¨ § ¥ ¥ ¥ • CMOS for optimum speed/power ing/reading operation of the memory.