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System Layout Planning Procedure

This procedure discusses some of the important considerations in planning the internal case layout of a system. This is a step that many people forget about when assembling a new PC, and as a result, they end up wasting a lot of time moving components around after they have been installed. Worse, poor planning increases the chances of problems with the system, especially due to cooling, that may not show up until weeks or months after the system has been installed. This procedure may also help those who have an existing system experiencing overheating problems; using the guidelines here you may want to make changes to how the system is laid out.

Note: This procedure isn't so much a set of step-by-step instructions like most of the others are, but more of a collection of specific items to take into account when preparing to build or rebuild a PC.

Procedure Overview:

• Difficulty Level: 2 (Low).
• Risk Factor: 1 (Very low).
• Hardware Required: None.
• Software Required: None.
• Time to Perform: Approximately 10-15 minutes.
• Preparation / Warnings:
  • Having the system case open in front of you makes this procedure much easier to do, because it allows for much easier visualization. For instructions on opening up the case, see here.
  • As usual, be careful when handling loose components, ground yourself first, and avoid touching anything made of metal.

Procedure Steps:

1. General Layout Planning Considerations:
   • It is almost always better to place components further away from each other than right next to each other. This means that if at all possible, leave space between expansion cards, hard disk drives, etc.  This improves cooling and reduces the chances of physical interference.
   • Items that generate a great deal of heat should be placed in a part of the case that will get more ventilation.
   • Always allow slack in planning the length of cables. A cable that just barely reaches between two components is much more likely to be pulled out accidentally.
   • You may want to very carefully place the loose motherboard into the system case in the approximate place where it is going to go. This will allow you to plan much better. Make sure you insulate the motherboard completely from the metal of the system case!
   • Similarly, you may want to temporarily slide the drives into their bays to see where their connectors end up. Be careful.
2. Plan Location of Drives: Plan where you are going to put the drives in your system. These are the factors you need to take into account:
   • Decide how many IDE channels you are going to use; see the section on setting hard disk and CD-ROM jumpers for more information on this. Then examine the distance between the IDE header(s) on the motherboard, and the drive bays in the case. Compare to the length of the IDE cables; obviously they have to reach. If you are going to put two devices on the same cable, make sure the cable will reach both drives.
   • Some IDE devices are sensitive to the length of the cable used. Shorter is better, all else being equal. You can get extended length IDE cables but I don't recommend it with newer drives. The standard IDE cable limit is 18 inches.
   • Check the distance of the floppy drive from the location of the floppy drive header pins on the motherboard, and compare to the length of the floppy cable. You can get extended-length floppy cables; the floppy is a low-speed device so this doesn't usually cause a problem.
   • Check the length of your CD audio cable. The CD-ROM drive cannot be further away from the sound card than the length of this cable.
   • Watch out for intereference between drives and the motherboard. In particular, the voltage regulator on modern motherboards can get very hot in operation, and you want to keep it away from hard disk drives. In general, I try to keep drives of all sorts away from the motherboard.
   • It is preferable to mount hard disk drives horizontally (label up), rather than vertically (on their side).
   • Some cases have a spot for mounting a hard disk at the very top of the case. This is usually not the best position for a hard disk, for two reasons: First, the ventilation in this part of the case is usually poor. Second, this part of the case is usually farthest from the motherboard, making it a stretch to get the cable to reach.
   • You can mount a 3.5" drive into a 5.25" drive bay using a mounting kit adapter available at most computer stores. If you are low on bays, it is best to use 3.5" bays for 3.5" drives whenever possible, since you can't go the other way. If you have a lot of bays, you may want to decide on where to put the drives based more on cooling considerations.
   • If the system is in a tower case that is going to be placed on the floor, it's easier for the user to reach the drive doors to change media in floppy or CD-ROM drives when they are towards the top of the case.
   • Count the number of drives that are going into the system. Then count the number of power plugs that come from the power supply. If the first number exceeds the second, you will need to purchase and use a "Y adapter" to split one of the plugs out for use by two devices.
   • Check the ability of the power plugs from the power supply to reach the drives in your planned locations.
3. Plan Location of Expansion Cards: There are a few considerations to take into account when planning which expansion card slots you are going to use for which devices:
   • Consider where the video, sound, network and other cards are going to go in the system and visualize whether they will conflict with any motherboard devices or drives in the system.
   • It is better not to place cards in adjacent slots. This allows for better cooling and makes it easier to see the card without having to remove it.
   • AT form factor motherboards usually have only a couple of slots that will accomodate a full-length card. Leave these open unless you need them. Put short cards in slots that can't take long cards due to their position with respect to the processor socket or voltage regulator.
   • Some slots may be directly next to pin headers or jumpers on some motherboards. Using these slots makes reaching the headers more difficult.
   • If your motherboard has a shared PCI/ISA slot, do not use it during the initial system setup unless absolutely necessary. It gives you more flexibility for future expansion, when you don't know which bus type you will need.

Next: Case Floor Relocation Procedure

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