Tyan Computer GX21 - Manual (Page 86)

78
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