Hi,

Can somebody explain to me what are
Instruction and Data Caches as found in NPE400/NPE-G1 machines
How are they different from Level1 and Level2 Caches ?

TIA,
Roopa

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"Roopa" <roopa.ravi@gmail.com> writes:

> Hi,
>
> Can somebody explain to me what are
> Instruction and Data Caches as found in NPE400/NPE-G1 machines
> How are they different from Level1 and Level2 Caches ?

The instruction cache is used to cache executable code, while the data
cache caches data.  Cache levels are an unrelated concept.  A typical
memory system looks something like this:

+---------------------+
|         CPU         |
+---------------------+
+---------+ +---------+
| I-cache | | D-cache |  Level 1
+---------+ +---------+
+---------------------+
|       Level 2       |
+---------------------+
+---------------------+
|         RAM         |
+---------------------+

The level 1 cache is split into instruction and data caches, both
backed by the (much larger) level 2 cache.

--
Måns Rullgård
mru@inprovide.com

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For my system running QNX, i know -

L2 cache = 256KB and L3 cache = 2048 KB

and upon printing the structures i get :

***Printing cpuinfo structure...

0) cpu:00002721 flags:c0000ac6 speed:00000106 cache i/d:1/0 name:46

***Printing cache attributes ...

0) flags:00000032 size:0020 #lines:512 control:8000b190 next:255
1) flags:00000011 size:0020 #lines:512 control:8000ae5c next:255

How does one know/deduce from these o/p the L2 cache = 256KB and L3 =
2048 KB. ?

Here is the link -
http://www.qnx.com/developers/docs/.../>
l#cacheattr

Actually 0020*512 should give the cache values right ?

TIA
- Roopa

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