interface directly with the VGA chip, without any PC-style bus.
According to my knowledge almost all comercial VGA chips I mean those which you see on your PC motherboards communicate with your system processor using PCI or ISA bus.
Considering the remote posibilty of finding a VGA chip which doesn't use a PC style bus and can be interfaced directly troubles wont be reduced. IF you want to use true motion graphical display Our main bottleneck with VGA display is 8052 speed. The VGA uses a resolution of 640X480 pixels and has a refresh rate of 60Hz thus to draw a frame on monitor screen you will need to send 640*480=307200 data units per frame thus to draw @ 60Hz you will need to send 307200*60=18432000 data units per second. If you are planning to use 8 bit color depth than your data unit is a byte. Thus you need to process and send 18432000 bytes every second. Now imagine how fast processor you will need.

The above applies only if full screen [640X480] motion display @ 60Hz is required. There might be [I am not sure] some VGA chips which can be interfaced directly just send them ascii data with control words and they will display it on VGA screen. In that case things will be simillar to HD44780 style LCD where you don't need a fast processor. Or there might be VGA chips which can display still graphics such as photos or images on VGA screen just send them bitmap pattern and they will display it on monitor in this case things will be simillar to GLCD interfacing you don't need a fast micro. But remeber if you are talking about true VGA with motion display you definately need a fast micro.

Regards,
Prahlad Purohit