Getting ahead of the curve.
It appears to me that if we use a bus interface for the chip that we
will always be behind the curve. IIUC, nVidia is/was selling boards
with a PCIe to PCI bridge to use their PCI chips -- behind the curve.
Sorry to get back to the graphics enabled northbridge chip, but this
appears to be the best architecture to me. The Intel G965 would work,
but this is just an example -- a ready made implementation of my idea.
The graphics northbridge has:
Frontside bus interface
VGA video controller
Memory controller
Video output.
that are needed.
This chip has an analog video output and 2 video expansion video
outputs. It can support two monitors. I wonder if the analog video
output is needed. IAC with a custom chip we wouldn't have it.
If we were to use the Intel chip, we would have a Pentium front side bus
to which we would attach a system bus interface chip (AGP, PCI, PCIe,
HTX, etc.) and the VGA BIOS ROM. It appears that it might be a good
idea to also attach a MCU and additional ROM to configure the chip at
boot and to make use of the built in graphics functions.
The Intel chip is very configurable and it contains a 2D and 3D video
accelerator. It also has an interface to a southbridge chip which could
be used to access other stuff.
If we were to make a custom chip for these functions, it would not need
to be as configurable and it could include an interface for the Video
BIOS ROM and a system space ROM.
So, if we were to make a custom chip it would have:
Front side bus
VGA video controller
Memory controller
Two serial video outputs
ROM interface
Such a chip could have some graphics functions, or not.
What is the advantage of this architecture?
1. It doesn't have the system bus interface built in so it is possible
to offer different system bus interfaces without making a new chip.
2. It might be possible to use existing commercial chips for the system
bus interface.
3. The architectures allows adding additional functions to the card.
4. Multiple chips would take less cooling.
5. However, the major advantage of this is that you can add additional
processors to the front side bus. You can add a MPU, ROM and multiple
GPU chips to the front side bus.
The question is cost. Would a multiple chip board cost more or less to
produce? IIUC, that depends on the volume being produced.
--
JRT
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