A core is usually the basic computation unit of the CPU – it can run a single program context (or multiple ones if it supports hardware threads such as hyperthreading on Intel CPUs), maintaining the correct program state, registers, and correct execution order, and performing the operations through ALUs. For optimization purposes, a core can also … Read more
Byte: Today, a byte is almost always 8 bit. However, that wasn’t always the case and there’s no “standard” or something that dictates this. Since 8 bits is a convenient number to work with it became the de facto standard. Word: The natural size with which a processor is handling data (the register size). The most common word sizes … Read more
A x64 native (AMD64 or Intel 64) processor is only mandated to support SSE and SSE2. SSE3 is supported by Intel Pentium 4 processors (“Prescott”), AMD Athlon 64 (“revision E”), AMD Phenom, and later processors. This means most, but not quite all, x64 capable CPUs should support SSE3. Supplemental SSE3 (SSSE3) is supported by Intel … Read more
A trap is an exception in a user process. It’s caused by division by zero or invalid memory access. It’s also the usual way to invoke a kernel routine (a system call) because those run with a higher priority than user code. Handling is synchronous (so the user code is suspended and continues afterwards). In … Read more
Your definition of a “conflict miss” is a bit unhelpful. A conflict miss occurs when a block is needed which existed in the cache before, but was evicted in favor of another block that had to be mapped to the same slot. In your example, the accesses to 13 and 25 are unique, so they … Read more
A byte is a memory unit for storage A memory chip is full of such bytes. Memory units are addressable. That is the only way we can use memory. In reality, memory is only byte addressable. It means: A binary address always points to a single byte only. A word is just a group of bytes – 2, 4, 8 depending upon the data bus size of the CPU. To understand the memory operation fully, you must be familiar with the various registers of the CPU and the memory ports of the RAM. I assume … Read more
When you create an instruction set, you’re bound by some constraints, such as the total number of instructions you can create. The MIPS creators realized that there isn’t a need for subi (because you can add a negative number with addi using 2’s complement), and they simply made the decision to forego making that instruction. It may have been … Read more
In x86 terminology/documentation, a “word” is 16 bits because x86 evolved out of 16-bit 8086. Changing the meaning of the term as extensions were added would have just been confusing, because Intel still had to document 16-bit mode and everything, and instruction mnemonics like cwd (sign-extend word to dword) bake the terminology into the ISA. x86 word = … Read more
The benefit of write-through to main memory is that it simplifies the design of the computer system. With write-through, the main memory always has an up-to-date copy of the line. So when a read is done, main memory can always reply with the requested data. If write-back is used, sometimes the up-to-date data is in … Read more
lw (load word) loads a word from memory to a register. $2 is the destination register and $4 the address register. And the source of information is the memory. 4 is an offset that is added (not multiplied) to the address register. This kind of memory access is called based addressing and is it quite … Read more