1.3 Ram Flashcards
RAM
Random Access Memory
ROM
Read Only Memory
PROM
Programmable ROM; Write once
EPROM
Erasable PROM; Write/Erase/Write again
EEPROM
Electrically Erasable PROM; Flash and SSD
SRAM
Static RAM Very Fast Very expensive Physically larger Often used in processor caches; L1, L2, L3
DRAM
Dynamic RAM
Always refreshing
Random Access
SDRAM
Synchronous DRAM
Synchronous with common system clock
How many pins on SDRAM
168 Pins
DDR RAM
Double Data Rate
Twice as fast as SDRAM; same clock speed
How many pins on DDR RAM
184 Pins
DDR-200 number of transfers per second
200 Million
Throughput of DDR-200
1,600 MB/s; 200 x 8; PC1600
DDR I/O Bus speed vs Memory speed
1:1
DDR speed vs clock speed
2:1
DDR speed vs Transfer Rate
1:8
DDR2 vs DDR
Twice as fast
Not backwards compatible
How many pins on DDR2 RAM
240
DDR2 I/O Bus speed vs Memory speed
2:1
DDR2 speed vs clock speed
2:1
DDR2 speed vs Transfer Rate
1:8
DDR3 vs DDR2
Twice as fast
Same clock rate
Larger capacities
Not backwards compatible
How many pins on DDR3 RAM
240
DDR3 I/O Bus speed vs Memory speed
4:1
DDR3 speed vs clock speed
2:1
DDR3 speed vs Transfer Rate
1:8
SO-DIMM
Small Outline DIMM
Used on critical computer system
Parity Memory
ECC
Parity Memory
Adds additional party bit
Not always accurate
Does not correct
ECC
Error Correcting Code
Detects and corrects on the fly
Not all systems use ECC
How parity works
Makes byte even with extra bit
Parity bit for 11100111
0
Parity bit for 00000010
1
Parity bit for 10011000
1
Is parity correct
00000111 1
Yes
Is parity correct
00000010 0
No
Is parity correct
01100100 1
Yes
Registered Memory
additional register between RAM and controller
Also known as “buffered” memory
Mostly used on servers
Multi-channel memory
Install in pairs/trios
Should be exactly same modules
Often coloured differently
Single-sided vs double-sided
Ranks; groups of memory on a module that can be independently accessed
Physically if chips on one side or both
