I want to basically make custom networking devices with a custom protocol. (switch device/PCI cards)

The basic principle of the design is, the switch will be controlled by an Intel CPU. I want incoming data to be read directly onto RAM in the switch, and then CHIP that will send back off the RAM as commanded the CPU.

The PCI cards I want to behave in very similar manner, just controlled by the computers processor.

Ideally, I would like the circuits between switches/PCI cards to be fairly high speed.

I need direction on how to build such a device, and what chips to use. I do not need the chips reading the data todo much else other than read, and basically be able to be programmed to stop reading after so much data has been read, and be programmed to read to a set space of memory. If it can generate an interrupt when its done its job, that would be good, but not essential. I will also need a chip that reads data off from the RAM when told by the CPU.

Almost all network interface chips do exactly what you explain above. Most have internal buffers also for caching stuff. All you need to add is a DMA controller chip and the CPU (with software) and you're done.

But even the humble NICs that are so cheap to buy do this also. Just program up a driver for your current PC and you are good to go.

Considering that simple NIC drivers can be written in few hundred lines of assembler, it isn't a huge task to make it support your own protocol on top of that.
http://code.google.com/p/baremetal/source/browse/trunk/os/drivers/net/rtl8139.asm

When you build your own, it takes time and money and testing.

How many of them would allow me then to implement the layer 2 protocol, as I don't wish to use Ethernet.

[edit] Actually, better question, so basically most network interface chips would read data received in raw without processing it in any way if told so, without any layer 2 processing?[/edit]

The chips I've worked with have no idea about protocols.

You can also implement non IEEE packet sizes. The chips are more powerful than most networks take advantage of due to lots of legacy. I think IPv6 intends to unleash some or all of this lost capability.