Imagedp4 Video Bios - Datapath ImageDP4 User Manual

ImageDP4 Video BIOS

The Intel x86 based architecture limits the amount of legacy I/O space available in a system to 64KB.
Hardware which requires I/O access can be mapped into this 64KB area. An ImageDP4 requests 256 Bytes
of legacy I/O. Unfortunately any PCIe bridge will align this to a 4KB boundary and so the I/O space
allocated to each ImageDP4 is actually 4KB.
64KB ÷ 4kB gives an absolute maximum of 16 ImageDP4 graphics cards. However, other system devices
also require legacy I/O. Often the Network Devices will request some I/O space, and so might the USB
devices and on-board graphics. It is not unusual for there to be I/O space available for only 8 ImageDP4
graphics cards when installing them in a complex server class motherboard.
There are a number of different BIOS types in operation as the computer boots. The "System BIOS" is
resident on the motherboard and is responsible for starting up all the hardware and mapping in the
resources (like the I/O) so that they are available to the CPU. The "Video BIOS" is resident on the
graphics cards. It is responsible for booting the GPU and for informing the System BIOS which resources
will be required for the GPU to operate correctly.
The System BIOS requires an I/O enabled ImageDP4 if it is used as the boot device, i.e. it provides the
graphics output that displays the BIOS boot messages. However the Windows driver for the ImageDP4
has been designed so that it does not require I/O. We can therefore use two types of Video BIOS for the
ImageDP4, one which requests I/O (and which can be used as a boot device) and one which does not. This
allows us to increase the number of ImageDP4 cards which can be used in a system.
To find out more about how to choose the correct BIOS for your requirements and how to update the
BIOS for the ImageDP4, download a PDF from our website by clicking on the link below or select it from
the Read Me file on the Software Installation Suite CD supplied with your ImageDP4 card:
www.datapath.co.uk