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Do 64-bit processors have 64-bit registers?
The x64 processor also provides several sets of floating-point registers: Eight 80-bit x87 registers. Eight 64-bit MMX registers. (These overlap with the x87 registers.)
Does MOV zero extend?
By guaranteeing it will always be zero extended to 64 bits, the compilers can work with this axiom in mind whilst in mov rdx, rax , rax only has to wait for its single dependency, meaning it can begin execution quicker and retire, freeing up execution units.
What’s the difference between x86 and x64?
x86 refers to a 32-bit CPU and operating system while x64 refers to a 64-bit CPU and operating system. Does having more amount of bits in each operating system have any benefits? In addition, with a 64-bit system, it will be more efficient as it can process data in 64-bit chunks compared to 32-bit chunks.
How many registers does a 64-bit CPU have?
8 registers
As well, 64-bit x86 includes SSE2, so each 64-bit x86 CPU has at least 8 registers (named XMM0–XMM7) that are 128 bits wide, but only accessible through SSE instructions.
What does zero extended mean?
In a move or convert operation, zero extension refers to setting the high bits of the destination to zero, rather than setting them to a copy of the most significant bit of the source.
Is it possible to access the higher part of the 32-bit and..?
So while there aren’t any direct instructions to specifically access the upper half of a 32- or 64-bit register, you can get to that data by using shift and rotate instructions (of which your choice of use mostly depends on if you care about maintaining the integrity of the bits in the lower-half of the registers).
Can a 32 bit register be moved to a 64 bit register?
You can move small immediate values to a 64-bit register by using existing (32-bit) instructions. It also saves you from having to encode 8 byte values for MOV RAX, 42, when MOV EAX, 42 can be reused. This optimization is not as important for 8 and 16 bit ops (because they are smaller), and changing the rules there would also break old code.
How are registry entries stored on 64-bit Windows?
On 64-bit Windows, portions of the registry entries are stored separately for 32-bit application and 64-bit applications and mapped into separate logical registry views using the registry redirector and registry reflection, because the 64-bit version of an application may use different registry keys and values than the 32-bit version.
Where can I Find my 32 bit registry?
However, if you compile your application as a 32 bit binary and run it on a 64 bit machine then your registry information is now located here: This means that if you run both the 32 bit and 64 bit versions of your application on the same machine then they will each be looking at a different set of registry keys.