TYAN TOMCAT I915 User Manual page 48

Tomcat i915 S5120
Generally, because of its FIFOs and the DMA channel it uses, ECP is good for large data
transfers (useful for scanners and printers). On the other hand, EPP is better with links that
switch directions frequently (like parallel port drives).
There are two versions of the EPP transfer protocol - EPP1.7 and EPP1.9. Generally, EPP1.9
is the preferred setting because it supports the newer EPP1.9 devices and most EPP1.7
devices; and offers advantages like support for longer cables. However, because certain
EPP1.7 devices cannot work properly with an EPP1.9 port, this BIOS feature was
implemented to allow you to set the EPP mode to EPP1.7 when such an issue occurs.
Therefore, it is recommended that you set this BIOS feature to EPP1.9. But if you have trouble
connecting to your parallel port device, switch to EPP1.7.
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
recommendation.
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 considered 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.
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
recommendation.
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Standard
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SPP
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EPP1.7
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EPP1.9
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ECP
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ECP + EPP
ECP Mode Use DMA
This BIOS feature determines which DMA channel the parallel port should use when it is in
ECP mode.
The ECP mode uses the DMA protocol to achieve data transfer rates of up to 2.5 Mbits/s and
provides symmetric bidirectional communications. For all this, it requires the use of a DMA
channel.
By default, the parallel port uses DMA Channel 3 when it is in ECP mode. This works fine in
most situations.
This feature is provided just in case one of your add-on cards requires the use of DMA
Channel 3. In such a case, you can use this BIOS feature to force the parallel port to use the
alternate DMA Channel 1.
Please note that there is no performance advantage in choosing DMA Channel 3 over DMA
Channel 1 or vice versa. As long as either Channel 3 or Channel 1 is available for your parallel
port to use, the parallel port will be able to function properly in ECP mode.
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3
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1
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Chapter 3: BIOS Setup