Properly document the different types of memory

coduin / epiphany-bsp

BSP implementation for the Parallella; the world's smallest supercomputer

https://jwbuurlage.github.io/epiphany-bsp/

GNU General Public License v3.0

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Properly document the different types of memory #12

Closed Tombana closed 9 years ago

Tombana commented 9 years ago

In the Epiphany library we find

E_EPI_GROUP memory for the Epiphany cores. 32 KB in size (0x8000)
E_SHARED_MEM allocated by e_shm_alloc (identified with a string).
E_EXT_MEM allocated by e_alloc which is called with size 32 MB in e_load_group

The difference between the latter two should be properly documented. This should include total size, read/write speed from the epiphany cores and read/write speed from the host processor.

Tombana commented 9 years ago

Differences are documented in include/common.h Speed benchmarking is still needed

Tombana commented 9 years ago

Speed benchmarks can be found at https://parallella.org/forums/viewtopic.php?f=23&t=307&sid=773cf3c3fc58f303645cfe0a684965a7

We have to document this in the wiki

Tombana commented 9 years ago

Some more things that are possibly confusing and need to be explained in the wiki:

SRAM static ram, refers to the hardware type of the memory. This is the memory of the epiphany cores
DRAM dynamic ram. This is the type of memory used at the host side. The external memory resides in here: although it is placed somewhere in the 1GB of memory, it is not visible by the linux kernel
SDRAM shared dynamic ram. This refers to the external memory (or sometimes to specific part of it labelled "shared_dram")

Tombana commented 9 years ago

Memory types are now documented at https://github.com/buurlage-wits/epiphany-bsp/wiki/Memory-on-the-parallella