Terry Hancock wrote:
Undoubtedly, you'd be running a small Linux or FreeBSD on the
X server card, and X would run in software on that CPU.
Yes, you would need some minimum Linux to support the X server and
handle the communication with the main PC.
Of course, you'd want to have a simple pass-through to allow
text-mode display from the main system (this might require some
magic, but the idea is that it would allow you to get to your system
if the X server had a problem. You'd be plugging your keyboard into
the X server, though, so you could catch a special keystroke or
something (maybe find a use for that stupid 'windows' key ;-) )).
Yes, you would need VGA hardware that would be the default on reset till
software activated X.
Hey! You've re-invented the X-Terminal! NCD would be proud...
Yeah, it's basically a thin-client built into a standard PC
daughterboard.
Isn't an X terminal considered to be a "thick-client"? :-)
I don't know, it'd probably cost more than it's worth (sorry but I'm
pretty clueless about estimating hardware expense), but it was an
interesting thought! :-)
Actually an AMD Geode-GX is in the under $30 range and includes VGA
hardware and some basic 2D graphics functions. The problem is that the
only way for a graphics accelerator to access its memory is through a 66
MHz 32 bit PCI. Clearly this could be bottle neck as it would also be
the interface to the main PC unless the Geode serial connection would be
faster. No heat dissipation issues since the 400 MHz is only 1.1 Watts.
The other alternative I can see, using existing parts, is to use an
Intel NorthBridge chip with graphics built in, with a processor and the
graphics accelerator sharing the front side bus with a CPLD to control
this. Interface to the PC could be through the north bridge's I/O bus
where I would use an existing PCI chip or a CPLD. Under 1GHz Celerons
are cheep, the only problem is that they need a heat sink and a fan.
AMD doesn't recommend Durons for new designs. AMD Geode NXs are low
power and have been upgraded by AMD to include some Athelon features.
The 1 GHz is only 6 Watts so you might need a small fan but no large
heat sink. Unfortunately, these are new and (therefore) aren't cheep.
Both possibilities leverage existing hardware to do the video output and
the memory controller so the ASIC doesn't have to do that.
In either case, you can have two price points. Either with or without
the GL hardware accelerator (this would be real simple with the Geode-GX
as it could be a PCI daughter card). The Geode or NorthBridge would
have some basic 2D acceleration.
You could also offer the NorthBridge without the CPU (no X server on
board) but you would need some sort of very low performance CPU to boot
the card -- read a ROM (or possibly from the PC's memory) and configure
the NorthBridge. Intel's DOX state that the NorthBridge can only be
configured from the processor bus so you either need a processor of some
sort there or put the card's interface (AGP, PCI, PCIe, etc) on the
processor bus. Perhaps having the card interface on the processor bus
is a better idea in any case.
--
JRT
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