Brian said:
Hi, I have a few questions about hardware and what it is. I looked here:
http://www.microsoft.com/en/us/sitemap.aspx
But there was no newsgroup. I use XP, so I need hardware. That's the only
way I can tie these questions into using this board. Anyways:
- What is an IEEE 1394 port (I think I have the number right). It seems
related to something about audio or video?
- What's a VGA port?
- What's a RJ-45 Ethernet connector?
- What is a serial port? What goes in it?
- What is an eSATA drive? Is it a newer SATA hard-drive? Is it better or
what's the difference?
- Why does RAM have to be in pairs (eg: 2-1Gb, or 2-512Mb, 2-2Gb)? I kind of
understand it interacts well or something, but why can't I use only one 2Gb
or 4Gb? Why can't I use a 1Gb and 2Gb combination or a 512Mb and 4gB (I think
I saw a 4gb in a store)? Can it be done, do you have to set some options up
for a non-same pair to work? Will it work?
- How can I tell when I need a new or larger power supply? If they are
overused do they burn out or crash and erase your system? I know there are
features to monitor my system, but how can I tell I have to upgrade a 300
Watt to a 500 Watt for instance?
- Can someone change their Processors? From what I'v seen, people seem to
sodder them on, or theya re already attached to the motherboard, but I think
this can be added to or changed. No?
- For what situations would someone recommend adding more that one fan in
your computer? How many hours of daily log-time or what situations make 2+
fans worth it?
Thank you.
Brian
If it is homework, it's going to be a long night.
The folks at Wikipedia write all sorts of articles. You can enter some of
your homework questions here. It does take a little skill to find stuff
here, because the articles aren't always located in the most straight forward
way. For example, "serial port" versus "RS-232".
http://www.wikipedia.org/
This would be for IEEE 1394. Otherwise known as Firewire. It is a communications
standard. It supports storage devices. It can also be used for networking (but such
a usage is not too common).
http://en.wikipedia.org/wiki/IEEE_1394
eSATA = External SATA, same as SATA only supporting the drive housed in an
external enclosure. Cabling is designed to make the cable last longer when
plugged and unplugged a lot. An eSATA cable is good for 5000 insertions.
*******
RAM is used in pairs, to operate in dual channel mode. One implementation of
it, operates two 64 bit DIMMs, as if they were a DIMM which is 128 bits wide.
That doubles the bandwidth on a burst transfer.
There are even situations where the computer has three memory channels, and
memory is used in triples. And it is done for the same reason, to enhance
memory bandwidth.
*******
When a power supply fails, it can damage equipment. It can ruin the motherboard.
It can ruin the hard drive. "Erasing a hard drive" would not be the result.
A hard drive could be damaged, but if it was, the rotating platters could
be recovered at a data recovery firm. Cost would be like $1000, but you could
get the data back. If the power supply ruins the motherboard, you replace it.
If the power supply ruins the hard drive, you install a new one. And if you're
lucky, a week from now the data recovery firm calls and tells you the data is
recovered and ready to deliver to your customer. You put the recovered data
back on the new hard drive.
*******
Fans are added to a computer case, according to the internal temperature target
the builder is aiming for. This is a formula for fan sizing. Use this as a
basic concept.
CFM = 3.16 x Watts / Delta_T_degrees_F
For example, say the room temperature is 25C. A "well cooled" computer case has
an internal temperature which is 7C degrees higher. 7C is the same as 10F Fahrenheit
degrees. Say you total up all the internal power consumption and get 200W of hardware.
(No, that is not the same as the power supply rating. You could be using a 500W
supply, but the supply might only be delivering 200W to the inside of the computer.
The 200W refers to the heat-producing watts, the ones being used by all the
hardware inside the box.)
CFM = (3.16 x 200) / 10 = 63.2 CFM (cubic feet per minute)
This fan gives 61.4CFM, but with no resistance to airflow. If the equipment
inside the computer continued to dissipate 200W, and you had a single fan
with 63.2CFM air moving capacity, then the internal temperature inside
the case would be 25C + 7C = 32C.
http://www.circuittest.com/English/Content/Items/CFA1212025LS.asp
You set the case temperature, according to how hot you want the hard drives to
get. The case temperature can be allowed to climb higher, but at the risk
to the hard drives. It is a balance between building a quiet computer, and
treating the hardware inside the box like royalty.
If you allow the CPU to go over 70C, the CPU begins to throttle back (run slower
automatically). If you find that is happening, then either the CPU fan
needs to be more powerful, or the case fan needs to be more powerful.
You can use the CPU power in watts, the theta_R for the CPU heatsink, to work
out the delta_T for the CPU. Knowing the CPU temp target of 70C, you work out
the delta_T for the amount of power it is dissipating. Say the heatsink gives
you a delta_T of 20C. 70C - 20C = 50C. The computer case can't get any hotter inside
than 50C. Say you allow the room to go up to 35C for the customer (that is the
external max temperature allowed for your computer build). That leaves 15C (27F)
for the above CFM equation. So it is possible to work it all backwards, use the
equation for CPU temperature, the equation for case temperature, and work out
what is required.
A retail Intel heatsink might be 0.33 C/W theta_R thermal resistance. Say the
processor is 65W. 0.33 C/W times 65W = 21C. The CPU will be 21C hotter than the
internal case air temperature. 70C - 21C = 49C max case temp. If the computer
is in a relatively tropical room at 35C, 49C - 35C = 14C for the CFM equation.
14C * 9/5 = 25.2F degrees. Again, we'll assume the total power inside the case
is 200W (yes, there is a way to work that out too
).
CFM = (3.16 x 200) / 25.2 = 25 CFM
You'll notice in that example, that the CPU got an "allowance" of 21C, while
the computer case allowance was 14C. You can juggle the noise of the CPU fan,
versus the case fan, according to your tastes. For example, if you put a
huge blower on the CPU, the case fan could be tiny and weak. But the customer
would be pissed off about the noise the CPU fan was making. You have to adjust
the sizes of both, to build a well balanced box. You can buy an after market
CPU cooler, to create a lower delta_T on the CPU, so that the case fan doesn't
have to work as hard. A good after market cooler might have a theta_R of
0.14C/W, versus the 0.33C/W of the heatsink/fan that comes in the Intel box.
You may need to find a book on HVAC (heating, ventilating, air conditioning), to
learn something about fan resistance curves, and how to add the effects of
multiple blowers. I don't know how to do that. But if you're sprinkling
seven fans on a tower case, you'd better know something about resistance
curves for fans, in order to understand why you're installing seven fans.
Frequently, multiple fans are dopey, because the builder set them up
so they're fighting with one another.
I don't have equations for everything, but as you can see, there is arithmetic
aplenty if you want it. And it might not all be conveniently in your
teacher's textbook.
*******
The CPU fits in a socket. You can undo the lever on the socket and remove
or replace the CPU. Solder is used on hardware where there is no intention
of allowing user replacement. The chips in your cell phone are likely all
soldered down.
Paul
