System information

10 Conclusion and Outlook
the CHARM has potential to improve the performance. With the aid of code optimization,
there will be place inside the FPGA to add functions to help the processing of the VGA
requests. Moreover, the VESA BIOS Extensions (VBE) provides a linear framebuffer format
[57]. The pixel data can be easily transformed into a VNC framebuffer using a linear frame
buffer instead of the several complex VGA frame buffer formats. The VBE is a display
standard to increase the limited screen resolution of VGA and to simplify the configuration
of the video frame buffer.
To improve the flexibility of the CHARM card, the cabling between the CHARM and
the host computer can be also reduced. The USB interface can be replaced by emulating
the same device with the PCI interface. The CHARM card can emulate a PCI host bridge
instead of a PCI VGA card. This approach has the advantage of the emulation of different
hardware devices behind the bridge. For example, the CHARM can act as a VGA and an
SCSI expansion card simultaneously. Thus, the boot device can be provided by emulating
an SCSI hard disc instead of a USB mass storage device. This approach reduces the need of
an USB connection. Another way to provide a boot device without using the USB interface
is to hook the boot interrupt 0x19 or implementing a BEV
1
[67]. Interrupt 0x19 provides
the bootstrap loader of a computer system and will be called by the BIOS after the POST
phase. With the aid of the CHARM RPC function, the boot code can get loaded from the
CHARM to the host computer. A Bootstrap Entry Vector (BEV) is a pointer that points
to a code inside an option ROM that will directly load an O/S [67]. For this approach, the
CHARM VGA BIOS code has to be expanded to a resident function which provides the
bootstrap entry vector. The cable activating the power and reset switch on the computer
main board can also be replaced. With the aid of the PCI PME
2
pin which is part of the
edge connector, the PCI device can request a change in the system power state [59]. The
PME pin provides the ability to wake computers.
The next generation of the CHARM card will be designed for PCI Express (PCIe). PCI
Express is a successor of the PCI Local bus [108]. Nowadays, PCI Express drives the PCI
Local Bus out of the market and it is the common interface for graphic cards. Using PCIe
for the CHARM card enables the usage of the CHARM for the future.
1
Bootstrap Entry Vector.
2
Power Management Event.
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