Understanding the basic components of a computer system
By:
        Conrad Pafford
                                  On:
                                        September 14, 2007

We will start by familiarizing ourselves with four main components, that when working together create a digital number crunching device that everyone is so intimidated by. The audience of this informational computer hardware introduction would ideally have a little experience with computer hardware and his/her goal would be to gain a better understanding and in turn build better computer systems.



Component 1:
Hard Disk Drive (HDD)- Fastest speeds (data transfer rates) for consumers are in the 300 MB/s range currently.
Purpose - Static (non-volatile storage)
Much slower than the CPU - which justifies an intermediate device known as Random Access Memory.
UDMA - Ultra Direct Memory Access - lessens processor utilization as HDD communicates directly with RAM



Component 2:
Randam Access Memory (RAM) Many speed variations exist - some of the fastest for computers transfer at 12,800 MB/s.
The above speed is DDR2 which transfers 6,400 MB/s per channel.
Purpose - Communication with CPU somewhat directly as it is much faster than the fastest hard drive.
Justification - Generates less heat & consumes less power than "static ram"



Important point 1 - RAM has something known as latency (specified by CL5<<5 cycles) which is the number of clock cycles it takes for RAM to process internally (1st data time in to 1st data time out; subsequent data at 1 clock on contiguous address)
Important point 2 - RAM is by nature Dynamic as in (DRAM) it uses capacitors which require electrical recharge as they hold data only for short times thus a refresh is required. Different RAM has different refresh rates and data cannot go in or out during these refreshes. The previous sentence justifies the need for a  "CPU cache" which is discussed in the CPU section below.



Component 3:
North Bridge - Communication data path between RAM and CPU. This chipset only exists on motherboards that are of type Intel (AMD processors have the circuitry imbedded within them).



Component 4:
Central Processing Unit (CPU or simply processor) - The CPU performs rapid mathematical calculation (much faster than RAM or the Hard Drive)
Type AMD - Internal Data Path size between L1 & L2 Cache = 128 bits 
Type Intel - Internal Data Path size between L1 & L2 Cache = 256 bits
The cache is responsible for storing data sent from RAM to the CPU so that maximum transfer rate can occur. Because the cache is "static" and not "dynamic" and uses a circuit known as a "flip-flop" it is as fast as the cpu because there is little or know latency due to a recharge or refresh.
Newer AMD 64 Processors support two external data busses --> Memory bus and hypertransport bus.



I hope this brief informative page helps people build better machines. There are many, many more aspects that need to be understood to build a computer efficiently but the above should get anyone started. Any questions or comments e-mail slpafford@pdscsansaba.com or call 325-372-4155 to schedule tutoring.



Link to motherboard websites -- Manufacturer Website Links
To calculate transfer rate:
width (of data path eg. 128 or 256) X clock rate (1) X data per cloth /8