Memory block type = "Auto" in RAM MegaWizard

[Altera_Forum]

When using "auto", is the memory block type fixed by the MegaWizard, or can it change later depending on the available resources?

[Altera_Forum]

Auto let's Quartus decide when fitting. So it can do a better job based on available resources(including if the hierarchy is in a LogicLock region, which limits resources). That being said, if the memory blocks are really full, I sometimes find it useful to force ones I know I want a certain way. I had one design where it kept switching what went into M9Ks and what went into M144Ks, which made things "hop around".

[Altera_Forum]

Ive also had experiences like Rysc. If you need something to behave in a particular way, it's usually easier to work it all out for yourself. My recent experiece is true-dual port rams. They only support 16 bit in mixed mode, so I had to do some external address decoding to be more efficient with the ram as I needed 16 bit writes and 32 bit reads.

[Altera_Forum]

One of the main purposes of using "auto", is not just to let Quartus decide based on resources usage, but also on which type of memory is supported by the specific device. 

 If your design is say, for an older family such as Stratix I and you use "M4K", then it won't compile when you move to newer Stratix families that replaced M4K with M9K blocks.