mike_biddell wrote:On the subject of Raspberry pi memory. The internal memory map has 256 mb, but there is potentially access to relatively unlimted memory on the SD card. (after all, the OS runs off that !!!). Although SD is slower than RAM, is it not just a case of organising the code to 'page' in some of the unused SD card memory. The choice of how that paging is done could minimise the speed loss downside. Does that make sense?
Access times for SD read/write are dreadfully slow, so it is not suitable for paging.
Also, an SD card cannot be written again and again and again. After a limited number of writes, the SD card will be destroyed. This is why an SD card cannot be used for paging or swap.
Before anybody asks, there will be a problem using a hard disk for the paging. There is no direct interface to a hard disk, it must go through the USB interface so this would add unacceptable delays.