cache memory

Any technical questions about the Epiphany chip and Parallella HW Platform.

Moderator: aolofsson

cache memory

Postby phadji19 » Sun May 15, 2016 5:40 pm

I would like to ask if anybody knows why there is no cache memory on Epiphany
phadji19
 
Posts: 9
Joined: Tue Mar 08, 2016 9:39 pm

Re: cache memory

Postby aolofsson » Sun May 15, 2016 7:30 pm

I suppose you mean multi layered hardware cache as is found most modern CPUs?
https://en.wikipedia.org/wiki/Cache_(computing)

The reasons I did not include hardware caches in Epiphany when arch was created in 2008:

1.) They are very inefficient (area + power)
2.) They don't scale well (imagine 1000' processors trying to access DRAM with a 1 % cache miss ratio)
3.) Cache coherence doesn't scale well
4.) Non-determinism, this is why for real time systems like (radios) they are often turned off.
User avatar
aolofsson
 
Posts: 1005
Joined: Tue Dec 11, 2012 6:59 pm
Location: Lexington, Massachusetts,USA

Re: cache memory

Postby puneet » Sun Jul 31, 2016 8:52 am

And what about the cache memory for the Cortex-A9 processors on the Zynq chip?
I am running Ubuntu 15.04, and lscpu command shows me no cache.

root@parallella:~# lscpu
Architecture: armv7l
Byte Order: Little Endian
CPU(s): 2
On-line CPU(s) list: 0,1
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 1
Model name: ARMv7 Processor rev 0 (v7l)
CPU max MHz: 666.6670
CPU min MHz: 333.3340
puneet
 
Posts: 1
Joined: Sun Jul 31, 2016 8:48 am

Re: cache memory

Postby sebraa » Tue Aug 02, 2016 2:08 pm

The Cortex-A9 processors are common off-the-shelf ARM processors and contain cache as per architecture specification. Check the "dmesg" output.
sebraa
 
Posts: 495
Joined: Mon Jul 21, 2014 7:54 pm


Return to Epiphany and Parallella Q & A

Who is online

Users browsing this forum: No registered users and 1 guest

cron