- Conceptual Overview
- Read-Only Memory (ROM)
- Random Access Memory (RAM)
- Cycles and Frequencies
- Summary—Basic Memory
- Cache Memory
- Memory Pages
- Rambus Memory (RDRAM)
- Double Data Rate SDRAM (DDR SDRAM)
- Video RAM (VRAM)
- Supplemental Information
- Packaging Modules
- Memory Diagnostics—Parity
- Exam Prep Questions
- Need to Know More?
We've seen that memory can be broadly divided into two categories: memory that the system can change, and that which the system cannot change. RAM and ROM, respectively, are the beginning concepts for understanding memory. The ROM BIOS is where the motherboard remembers the most basic instructions about the hardware of a particular chipset. CMOS stores system configuration settings, as well as settings for additional hardware connected to the basic chipset. BIOS and CMOS are different in that CMOS requires a small amount of electricity to maintain its settings.
BIOS and CMOS can be changed, but not without some effort. Make sure you know the acronyms associated with these chips and the ways in which they can be updated. Additionally, you should have a comfortable understanding about the following points having to do with memory:
The central processing unit, the memory controller, and the system clock
Clock cycles and multipliers, and how electrical data pulses are "pushed" along by clock pulses
How timing affects performance, and the difference between asynchronous and synchronous data transfers
The North Bridge and South Bridge architecture (see Chapter 2), and how the front side bus stands between the CPU and the North Bridge
We've talked about the original DRAM chips, and how they became SDRAM chips. The important change was when the memory controllers began to use timing frequencies to perform reads, writes, and refreshes. We've also examined the concept of timing oscillators and how their frequency can be divided into multipliers. Notice how we refer to the CPU speed as a multiple of slowest speed, and rarely as a fraction of a faster speed (a good marketing technique).
DRAM and SDRAM are both different from BIOS and CMOS. Be sure you know the acronyms, because you'll find them on the exam. SIMMs and DIMMs are modules, and we'll be discussing them shortly. Memory chips use different components as storage cells. After the chip has been manufactured, it's packaged onto a module. The individual chips fit onto a small IC board to form a module.