Slowly getting there with the GBS82XX boards, with some other contributors we are improving the board.
The speckle problem was caused by two contributing factors, SDRAM running at max speed and the Amiga's 5V CMOS signals. Slowing the SDRAM to 128 MHz (from 162) fixed most speckles. There is enough video bandwidth to upscale to 1280x1024. The 5V sync signals from the Amiga will damage the 3.3V GBS-82XX, in 1-2 years time! A 680 ohm resistor reduces the level nicely.
A 5V 750-1000mA switchmode power supply is fine. With the GBS-8200, a 500mA will do. Only one capacitor needs to be replaced, it's the 10uF ceramic by IC5 (1.8V supply), it must change to a Tantalum. This fixes the power supply issues as the converter was unstable with a zero in the feedback network caused by a ceramic.
Adding details to my blog;
http://ianstedman.wordpress.com/gbs-82xx-experiments/Turning off the bob and weave de-interlacer and line doubling provides nice 240/288p progressive video. For interlace modes we need to re-enable the de-interlacer.
The next steps are fine tuning of settings and some noise removal.
A firmware update is planned for the board. If you have a Raspberry Pi, you can experiment today
The chip in the GBS-82XX is very capable and reasonably well documented, it the configuration firmware that lets it down. It can up-scale to HD modes.
Ian
