Q: vxWorks without MMU

[Ran Shalit]

Hello,

I would like to ask a question regarding using vxWorks without MMU:
in "vxworks_application_programmers_guide_6.7" it is said:
"
The advantages of a configuration without MMU support are that it
....
The address space is limited to the available system RAM, which is
typically
smaller than it would be available on systems with MMU-based address
translation enabled. Because of the smaller address space, a system is
more
likely to run out of large contiguous blocks of memory due to
fragmentation"

My question is: why a configuration without MMU is more limited in
memory ? Does this passage mean that we use swap and other memory such
as flash in the configuration without MMU?

Thank you very much,
Ran

[Yong Wu]

My understanding is: without MMU, you cannot use virtual memory, so the largest range depends on your real phisical ram. further more, since you can only use real ram space, the phisical ram space used be fragemented during use. then the largest size you can allocate is the largest fragment.