what is the actual difference between physical memory and total memory

[Network_Sarovani]

Hello Experts , 

Output of  "show version" shows that the switch has 1.98GB of memory. However, I see with "show memory" that the whole total memory between Processor, I/O and Driver is 538MB .

what is the actual difference between physical memory and total memory ? 

 

[Jon Marshall]

My understanding is that physical memory is the total amount of memory the device has. 

Total memory in the "sh memory" output is the memory left after the image has been loaded into memory and the necessary data structures created etc. which would explain the difference between the two. 

That's my understanding but could be wrong. 

Jon

[Georg Pauwen]

Hello,

I think Jon is right on the money. The 'show memory' command shows the amount of memory that is left after the decompressed IOS file has been subtracted. I don't remember the compression ratio, I think it used to be 2 (meaning the IOS file size that is downloaded expands to twice that size in memory on the router).

[Network_Sarovani]

But when we calculate the %  , which value we should use to calculate the %  of Memory free ? 2GB or 538MB as total memory ?