Lecture 4 Flashcards
How is memory capacity specified?
By word size (8,16,32 bits) and number of bytes stored.
What is the unit of transfer?
Governed by data bus width, equal to number of bits that can be read/written at a time.
External memory transferred in larger units than a word: blocks.
What are four memory access methods?
Sequential (magnetic tape), Direct (jumping to vicinity plus sequential), Random (exact addresses, RAM), Associative (cache, comparison).
What are three performance parameters for memory?
Access time, memory cycle times (access time plus time before next access), transfer rate.
What are four physical types of memory?
Semiconductor (RAM/ROM), magnetic surface (DISK,TAPE), optical (DVD), magneto-optical (removable disk).
What are four physical characteristics of memory?
Decay, volatility, erasability, power consumption
What is a key design issue for RAM?
Memory layout or organisation
What are the three levels f memory hierarchy top to bottom?
Inboard, outboard, off line.
As we move from top to bottom with memory hierarchy what four factors change?
Cost per bit decreases, capacity increases, access time increases, frequency of access decreases.
What are two categories of registers?
User-Visible and Control/Status.
User Visible include AC, Data & Address.
Control include PC, IR, MBR, MAR, PSW
What are two main types of RAM?
DRAM: dynamic (refreshed frequently), simple (bits stored as charges in capacitors), allows high density & cheap.
SRAM: Static, uses flip flops, fast, complex so more expensive and needs more space, no refresh needed so faster, used in cache.
What are the five advanced DRAM technologies?
Enchanced, cache dram, sdram, rdram, sldram.
What is edram.
Enhanced dram is a combination of sram and dram. A small sram cache is included.
What is cache dram?
Takes advantage of small cache. SRAM component is larger than in edram.
What is Sdram?
Synchronous dram, synchronized with cpu clock, cpu doesn’t have to wait.
