How can I use Altera's HP DDR controller for fast 8x64 read?

You can configure your masters to do bursts of 8. SoPC builder will automatically add burst adapters between your masters and the DDR controller (which only does a burst of 2). If that doesn't take care of it, you could add a single pipeline bridge between all the masters and the DDR controller. This may improve performance at the expense of higher latency.