RAM Chapter 5

Understanding DRAM Organizing RAM Practical DRAM DRAM Sticks 64K x 1, 256K x 1 -> 8 bit Practical DRAM Intel 8088 had 1 byte frontside bus. Required two reads or writes. Cost issues DRAM Sticks X4, x8, x16 memory chips Single Inline Memory Module Consumer RAM Capacity organization’s most important concept

Types of RAM SDRAM – Synchronous Dynamic Random Access Memory Synched to the system clock DIMM Mostly 64-bit Banks of memory RDRAM – Rambus DRAM Dual channel architecture. Must be installed in pairs. MCC alternated between RIMMs CRIMM – continuity RIMM Proprietary. Expensive. Intel only.

Types of RAM DDR SDRAM – Double Data Rate SDRAM DDR2 DDR3 Read/write twice per clock cycle Table 5-1 DDR2 Clock doubled I/O circuits Cache on the module Table 5-2 DDR3 Table 5-3 Doubles buffer size Can overclock RAM Triple-channel memory

Types of RAM DDR3L/DDR3U DDR4 Low voltage Higher densities Lower voltages

RAM Variations Double-sided DIMM Latency Parity and ECC Chips on both sides of the module Physical space may be an issue Latency There is a time lag between when the MCC requests and the module returns data There is a time lag between possible requests CL2 or CL3 wait 2 or 3 clock cycles between actions Parity and ECC Stores extra bits to detect memory errors Registered and Buffered Memory A register is added to the module to act as a buffer between the module and the memory controller

Working with RAM Do you need more RAM? Getting the right RAM Virtual Memory Disk thrashing Pagefile.sys System RAM Recommendations 32-bit Windows: 2GB; 4 GB better 64-bit Windows: 4GB; 8GB better; 16+GB for processor intensive programs Control Panel ReadyBoost Can use flash device as virtual memory Getting the right RAM