[chbot] FPGA stuff

[Charles Manning]

Hi All

A few points on FPGAs...

1) Mark said that the Nios (Altera's soft core)  was equivalent to the ARM. 
While it is a RISC and is little endian it does not seem to be compatible 
with ARM, just comparable to.

All the vendors have some sort of softcores. Normally freebie 8-bitters and 
paid IP for the larger parts.

A lot of free stuff is available on opencores.org

2) What are they used for? Well pretty much anything that can use a mix of 
logic and CPUs. Xilinx had a very nice page of design examples on their 
website a few years ago but I cannot find it now. Some example applications:

* Set top boxes/ digital TV: Custom logic to perform correlation etc for 
decoding the signals, MPEG image decoding, HDMI encoding while a softcore CPU 
does the management + menus etc. In DVD players FPGAs are often used to do 
the error correction etc.

* Electric guitar: 
http://www.embeddedstar.com/press/content/2004/1/embedded12299.html Gibson 
guitars made an electric guitar around a Xilinx FPGA. The FPGA runs all the 
controls as well as well as providing custom digital interfaces (midi etc) 
and DSP to make all the sound effects.

More recently Gibson have moved to Altera which shows that VHDL can be highly 
portable 

* Printers: Many laser printers etc use FPGAs for image processing since that 
is way, way faster than software.

Mark mentioned the idea of having custom instructions in an extended CPU 
architecture - an idea that fits in with WISC (Writable Instruction Set 
Computing). This is really handy for image processing were you likely have to 
merge images, apply a bitmasks and such. With regular general purpose CPUS 
you might have to apply many instructions to apply the processing. With WISC 
it can be just a single instruction.

-- Charles