Well... what can I say, probably *all* USB Display Adapters use the same kind of chipset: The DisplayLink DL-120 or DL-160 (latter has the higher resolutions). I opened the box and the thing consists of only three chips. The very fat ASIC BGA DL-120, a DVI encoder chip and 16MB of DDR memory. 16 MB, seems a lot for an adapter that can only display 1280x1024 in 24 bit. But then again, it surely has at least two frame buffers (double buffering) to avoid tearing effects and probably a rather large decompression buffer for the compressed data. The device only has one bulk output with 512 bytes per packet and on interrupt in endpoint. The rest is done via control transfers.
This means, there is no way the to read back pixels from the framebuffer on the adapter, only a "write to memory" feature. This means the Amiga has to have a copy of the current framebuffer in memory. One could save the memory for the delta buffer, if the MMU would be used to calculate accesses (like the Savage Shapeshifter driver).
Except for the decompression, I expect the device to be rather simple hardwarewise -- maybe the registers of the DVI encoder chip are directly accessible over control transfers. If that's the case, luckily the docs of the chip are available on the net.
I'll keep you informed how it turns out. But I really need some more sleep...
