Memory and Secondary Memory Devices RDRAM vs DDR SDRAM MEMS disk alternatives Flash Memory IBM Microdisk Brian Hanczaryk Albert Meixner

RDRAM Power Modes Read/write transaction Active 1.0x mW 1.0x ns 100x ns 0.1x ns Nap 0.1x mW PowerDown.01x mW Standby 0.6x mW

RDRAM Advantages Disadvantages High clock speeds Bus effectiveness 85% Cost (128 MB -> $1000) Higher latency Operates at high temperature

DDR SDRAM Advantages Disadvantages Comparable bandwidth levels Lower latency Cost Poor bus efficiency 65% not by Intel

RDRAM vs DDR SDRAM

MEMS-Based Storage Devices Microelectromechanical systems (MEMS) –could improve storage hierarchies –replace disks (portable, wearable) –compliment disks (caches for RAID) Mechanical & Layout characteristics determine performance Simulation model –access times 6.5X faster –3X improvement of end-to-end performance

Data Org. of MEMS-Based Storage

IBM MicroDrive Fits into PCMCIA card slots Designed for Digital Cameras, PDAs, … 170MB, 340MB, 512MB, 1G Power Save Support (ABLE-2) Automatically switches, between Performance Idle, Low Power Idle, Standby and Sleep

IBM MicroDrive Advantages Disadvantages High Bandwidth 4MB-6MB/sec High Capactiy MB Low Cost 0.6$/MB High Power Consumption Standby 80mA, Read 300mA Less Robust Than Memory 150G operational High Latency Latency ~7ms, Seek ~15ms

FlashMemory A type of EEPROM chip no mechanical parts Solid State Storage Device Keeps data without power supply Widely used in Digital Cameras, PDAs, Cell Phones… CompactFlash (PCMCIA), Sony MemoryStick, Sega VMU, …

Flash Memory Advantages Disadvantages Low Latency High Bandwidth 4-6 MB/s Robust 2000G Low Power Consumption Sleep 0.5 mA, Read 46-75mA Low Capacity <200MB High Cost ~1.6$/MB