Registered modules, which are used in newer Fast RAM modules, contain a register that delays all information transferred to the module by one clock cycle, allowing the information to be buffered before going to the controller.

Serial Presence Detect (SPD) is a small EEPROM that resides on newer fast RAM DIMMS. When a computer system boots up, it detects the configuration of the memory modules in order to run properly.

RIMM

RDRAM memory modules are called Rambus Inline Memory Modules (RIMM) and contain 184 pins. Because RDRAM works in channels, any empty sockets have to be filled with a blank memory module called a Continuity Rambus Inline Memory Module.

Linux memory considerations

All types of memory — EDO, DRAM, and SDRAM — can be used with Linux. The only problem that you may run into is that older Linux kernels may not recognize an amount of RAM of 64MB. If you run into this problem, you need to pass parameters to the kernel from the LILO (Linux Loader) configuration file in /etc/lilo.conf:

append=”mem=<amount of RAM>M”

If you have 128MB or RAM, enter the following:

append=”mem=128M”

Don’t state an amount of memory that you don’t have, or your system may crash.

System Resources

7.5 Assure that system hardware is configured correctly prior to installation (e.g, IRQs, BIOS, DMA, SCSI, cabling) settings by identifying available IRQs, DMAs, and I/O addresses and procedures for device installation and configuration

To function properly, devices and peripherals must be able to communicate directly with the system resources, such as the CPU, memory, and disk drives. To facilitate this process, and to ensure that a device can talk to these resources when needed, the computer assigns certain lines and channels for that particular device to operate on. This allows the computer’s resources to be allocated and shared among all the devices. These resources are Interrupt Request Lines (IRQ), Input/Output addresses, and Direct Memory Access (DMA) channels.

Pay close attention to some of the system resources that are used for popular devices, such as floppy drives or sound cards.

IRQ

Interrupt Request Lines (IRQs) allow a device to communicate directly with the CPU. The process of getting the computer’s attention is referred to as “using an interrupt.” The name accurately describes its use because the device will actually interrupt the CPU to allocate a resource to it. IRQs are assigned by numbers from 0 to 15. Each device is assigned its own IRQ to use. No more than one device can use the same interrupt or a conflict will occur, causing the device to not function properly. Some devices actually share IRQs, including serial COM ports. Table 19-1 summarizes a list of common IRQs and the devices that use them.

Table 19-1

Standard Interrupts and Device Assignments