The advanced load address table (ALAT) is a functional unit in the Intel Itanium processor architecture. It is implemented with an associative memory. The ALAT is used to store information related to advance load instructions, as part of the speculative execution process.
An "advanced load" is a method aimed in reducing the latency of costly load operations. If there is a possibility that a data item will be required, the program may specify its advanced load, even before the confirmation that the item will be needed.
In the Itanium architecture, this advanced load order may be issued by an ld.a instruction. This instruction allocates an entry in the advanced load address table and starts the data transfer. The ALAT is used to identify the address from where the data will be read, the length of the required data block, the destination register and the state of the load operation. The success of the advanced load may then be checked with a ld.c or chk.a instruction that looks for the related information in the ALAT.
The ALAT in the original Itanium processor was implemented by a two-way set-associative memory with 32 entries. In the Itanium 2, this unit was changed to a 32 entries fully associative structure. This design required extra hardware elements (longer memory tags, and more tag comparators) but it improved performance of speculative programs since cache miss due to mapping conflicts is avoided.
Famous quotes containing the words advanced, load, address and/or table:
“Only conservatives believe that subversion is still being carried on in the arts and that society is being shaken by it.... Advanced art today is no longer a cause—it contains no moral imperative. There is no virtue in clinging to principles and standards, no vice in selling or in selling out.”
—Harold Rosenberg (1906–1978)
“Rich are the sea-gods:Mwho gives gifts but they?
They grope the sea for pearls, but more than pearls:
They pluck Force thence, and give it to the wise.
Every wave is wealth to Daedalus,
Wealth to the cunning artist who can work
This matchless strength. Where shall he find, O waves!
A load your Atlas shoulders cannot lift?”
—Ralph Waldo Emerson (1803–1882)
“Give a boy address and accomplishments and you give him the mastery of palaces and fortunes where he goes.”
—Ralph Waldo Emerson (1803–1882)
“Comes the time when it’s later
and onto your table the headwaiter
puts the bill,”
—Robert Creeley (b. 1926)