Enum Width 

pub enum Width {
    Single32,
    Single64,
    Block128,
    Block256,
}

Transfer size, encoded in SysCmd(1:0) of a request.

Variants

Single32

32-bit single transfer. All 8/16/24/32-bit reads are issued as this; the CPU does the shifting internally.

Single64

64-bit.

Block128

128-bit block — a D-cache line.

Block256

256-bit block — an I-cache line.

Implementations

impl Width

pub const fn bytes(self) -> u32

Bytes moved.

pub const fn beats(self) -> u32

32-bit beats on the bus, which is what the data phase costs.

The VR4300’s SysAD is 32 bits wide, not 64. This is the headline cost reduction against the R4400 and it is easy to get wrong, because the CPU is a 64-bit machine internally and most MIPS III documentation describes a 64-bit external bus. The manual is explicit (§1.3): “It contains a 32-bit multiplexed address/data bus, with per-byte parity … It is not compatible with the System interface bus used on the VR4400”, and every signal reference in it is SysAD(31:0).

So a 128-bit D-cache line is 4 beats and a 256-bit I-cache line is 8, not 2 and 4. Halving these would make every cache fill finish twice as fast as hardware.

Trait Implementations

impl Clone for Width

fn clone(&self) -> Width

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Width

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Width

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Hash for Width

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Width

fn eq(&self, other: &Width) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Width

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Width

impl Eq for Width

impl StructuralPartialEq for Width