Technical Upgrading A Computer Installing A SCSI Card

Installing A SCSI Expansion Card

Although much of SCSI (Small Computer System Interface) acclaim has been shrouded in recent years (again) by Enhanced IDE which offers great performance, ease of installation and value for money but the basic strengths of SCSI still outweigh EIDE and is the interface of choice for serious multimedia work, file and application servers. While EIDE can deliver high transfer rates the method of transferring requires a degree of main processor involvement which effects the processors other requirements. This problem isn't there with SCSI simply because the data transfers are controlled by the host adapter, using far fewer, if any processor cycles.

SCSI is a system interface rather than a device interface which is only designed to work with specific devices. A system interface is more general purpose and can match with virtually any kind of device.

If you are using 32 bit operating system from Microsoft it is simply a matter of installing the hardware. If you are not running Plug and Play you will need to know the IRQ, DMA and I/O ports already used by your personal computer and avoid any hardware conflicts. Adjust the settings on the SCSI card before you fit it. Most common brands of SCSI host adapters are both plug and play with dip switches or jumpers for non-plug and play. Some boards label PnP as software configurable.

Take the normal safety precautions and power down your computer, unplug from the mains and disconnect all the leads. Earth yourself before handling any electrical components by simply touching a metal pipe or the chassis of your computer. If you are paranoid you could try an antistatic wrist-strap and earth your workbench.
Unscrew any self tapers and take the lid off the machine. If you need to do any discovering of hardware resources do that first. Choose a free suitable expansion slot, undo the bolt securing the blanking plate at the end of the slot and remove the blanking plate. Choose a 16 bit expansion slot if you are fitting an ISA card or a 32 bit slot for a PCI card.

Hold the card firmly by its top edge and press down until its gold edge connector is firmly seated in the expansion slot. Watch how you treat any external clips on the SCSI card face plate as they often get in the way. Fit the screw to tighten the card. If you are installing any internal SCSI devices, set their ID and termination before fitting them in your drive bays. Make sure your internal SCSI ribbon has enough connectors for all your devices, hook up the ribbon cable to the internal SCSI devices and note the coloured edge of the ribbon cable aligns with pin 1 at each end. If you are installing a bootable SCSI hard drive as well you need to change settings in the CMOS setup.

Put the lid back on, do up the screws back up and plug everything back in including any external SCSI devices. Power up the personal computer and ensure that it all still works. A listing from the SCSI devices may appear after the video BIOS, listing all the SCSI devices found.

If you have installed a new SCSI hard drive, you will need to partition it. If at this point something is wrong and everything is fitted correctly, it is likely a resource conflict. If it is not an IRQ, I/O or ROM BIOS address overlap look for obvious things like two SCSI devices with the same ID number, a missing terminator plug or simply a device that hasn't yet been powered on. Sometimes swapping a shorter cable for a longer one and vice versa or moving devices to a different connector can work.

SCSI ID uniquely identifies every SCSI device, including the host adapter. There are eight SCSI IDs on a single channel and typically the host adapter takes ID 7. As long as the ID is unique you can start using any other ID. Higher numbers get a higher priority. Normally a boot device has to be ID 0 or 1.
Self Configuring Auto Magically (SCAM) SCSI devices need no user intervention and automatically allocate SCSI IDs.

Each end of the SCSI chain needs terminated. A terminator consists of resistors that prevents excess signals bouncing back along the bus causing problems. The terminator can be a plug, pack or dip switches

Internal SCSI devices all connect using a 50 pin ribbon cable and with up to eight connectors or as many drives as you plan for. External connectors are far from standard. A 25 pin plug, a 50 pin Centronics style connector, SCSI -2 50 pin high density connectors and so on.

The drivers supplied with your card are likely to be newer than the ones that are a part of the Windows operating system. Check the SCSI card manufacturers web pages for any new developments and possibly updates for the firmware or operating system.

Installing A Hard Drive