new components: cam and replacement #259
Conversation
removed wavedumper
lib/src/memory/cam.dart
Outdated
| final int idWidth; | ||
|
|
||
| /// The "enable" bit for this interface, enabling a request. | ||
| Logic get en => port('en'); |
There was a problem hiding this comment.
why do we need an enable bit?
There was a problem hiding this comment.
To tell it to do the cam match. You are providing a tag in, and the en tells it to do a match and return the idx or data back. This is the same as a DataPortInterface providing an en and addr. Just replace those with en and tag.
You may not want it doing a match if you simply have the tag field set on the read port.
There was a problem hiding this comment.
the enable is needed for a write, but if you're doing a read isn't it the same if we just always read whatever address is given? what do you mean "doing a match"? is this for power savings? the combo logic is there either way
There was a problem hiding this comment.
Good point and simpler is better.
|
|
||
| /// An interface to a Content-Addressable Memory (CAM) that allows querying | ||
| /// for tags and returns the index of the matching tag if found. | ||
| class TagInterface extends Interface<DataPortGroup> { |
There was a problem hiding this comment.
but i only see it used in one way, and the write ports are DataPortInterfaces. Is there another place you're planning to use them?
lib/src/memory/cam.dart
Outdated
| final int idWidth; | ||
|
|
||
| /// The "enable" bit for this interface, enabling a request. | ||
| Logic get en => port('en'); |
There was a problem hiding this comment.
the enable is needed for a write, but if you're doing a read isn't it the same if we just always read whatever address is given? what do you mean "doing a match"? is this for power savings? the combo logic is there either way
| String? logicName, | ||
| }) : super(fields, name: logicName ?? config.name); | ||
|
|
||
| // Historically the CSR disallowed renaming because the architectural |
There was a problem hiding this comment.
these test files are getting pretty long. is there an opportunity to refactor a bit to reduce repetition by making some reusable infra?
2 participants
Description & Motivation
These are two components needed to build various kinds of cache memory.
First is a CAM which is a contents-addressable memory. It addresses memory by using a tag instead of an address.
It primarily returns a 'hit' but also the address of where it is found (we can work to make this optional).
The CAM also provides a standard write interface for populating the tags as data, using the line address.
Second is a Replacement module which is abstract and one kind of policy implemented; pseudoLRU. This will eventually be an optional Module passed into a Cache that can be used to modify a Cache with different way replacement policies.
Related Issue(s)
None.
Testing
Basic testing of the CAM to allow for simultaneous tag writes then tag lookups.
Backwards-compatibility
No.
Documentation
No.