Tyan Computer B5102, GX21 manual Onboard Parallel Port, 378/IRQ7 / 278/IRQ5 / 3BC/IRQ7 / Disabled

Onboard Parallel Port

To use the parallel port on the system, select an address and corresponding interrupt for the parallel port. The possible val- ues are:

378/IRQ7 / 278/IRQ5 / 3BC/IRQ7 / Disabled

Parallel Port Mode

This option allows the user to select the parallel port mode. This is linked to the parallel port so if you disable the parallel port, this feature will not appear or will appear greyed out.

There are four options. The default value is Normal (SPP) which will work with all parallel port devices. However, it is the slowest transfer mode and should only be used when faster transfer modes cannot be used.

There are two faster bidirectional modes available - the ECP (Extended Capabilities Port) and EPP (Enhanced Parallel Port) modes. ECP uses the DMA protocol to achieve data transfer rates of up to 2.5Mbits/s and provides symmetric bidirectional communication. On the other hand, EPP uses existing parallel port signals to provide asymmetric bidirec- tional communication.

Generally, because of its FIFOs and the DMA channel it uses, ECP is good for large data transfers (useful for scan- ners and printers). On the other hand, EPP is better with links that switch directions frequently (like parallel port drives).

However, the manufacturer of your parallel port peripheral may have designated a preferred parallel port mode for the device in question. In that case, it's best to follow their recom- mendation.

For those who don't know what mode to select but at least know that their parallel port device supports bidirectional transfers, the BIOS offers the ECP+EPP mode. If you select this mode, then the parallel port device will be able to use either one of those modes. However, this should be consid- ered as a last resort as you may be needlessly tying up an IRQ for nothing if your device does not use ECP at all. Or, the BIOS may not select the best parallel port mode for the device. If possible, set the parallel port to the transfer mode that best suits your parallel port device. The choices are:

SPP / EPP / ECP / ECP+EPP

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