What are the sizes of tword, oword and yword operands?

Question

What are the sizes of tword, oword and yword operands, as used in the NASM/YASM manual? And on a related note, is there a trick or und

Answer 1

Looking at the nasm source, it looks like:

• 'oword'/'DO' is 8 times as big as "word" (O for "octoword"), synonymous with dqword ("double-quad"); that would be 128 bits, corresponding to the size of an SSE vector register.
• 'tword'/'DT' is 80 bits (T for "ten bytes"), the full size of an Intel x87 floating point register.
• 'yword'/'DY' is 256 bits, and the Y is presumably mnemonic for the YMM names of the 256-bit vector registers in the Intel AVX extensions.
• 'zword'/'DZ' is 512 bits, Z for the ZMM names of the 512-bit vector registers in the Intel AVX-512 extensions.

So, it's not exactly a logical naming convention; "it just growed".