In a manner of speaking, when you perform array (“indexed”) type addressing with general registers, you are doing essentially the same thing as the segment registers. In the bad old days of 8-bit and 16-bit programming, many applications required much more data (and occasionally more code) than a 16-bit address could reach. So many CPUs … Read more
I wrote librdrand. It’s a very basic set of routines to use the RdRand instruction to fill buffers with random numbers. The performance data we showed at IDF is from test software I wrote that spawns a number of threads using pthreads in Linux. Each thread pulls fills a memory buffer with random numbers using … Read more
Revisited, August 2014 Prompted by Arnaud Bouchez in a recent comment, and in view of other answers and comments, I acknowledge that the original answer needs to be altered or for the least qualified. I left the original as-is, at the end, for reference. First, and maybe most important, a fair answer to the question … Read more
3.1.1.1 Opcode Column in the Instruction Summary Table (Instructions without VEX Prefix) The “Opcode” column in the table above shows the object code produced for each form of the instruction. When possible, codes are given as hexadecimal bytes in the same order in which they appear in memory. Definitions of entries other than hexadecimal bytes … Read more
The physical address is calculated from 2 parts. i) segment address. ii) offset address. The CS(code segment register) is used to address the code segment of the memory i.e a location in the memory where the code is stored. The IP(Instruction pointer) contains the offset within the code segment of the memory. Hence CS:IP is … Read more
Updated I’ve got no explanation for you, since I’m on Haswell, but I do have code to share that might help you or someone else with Broadwell or Skylake hardware isolate your problem. If you could please run it on your machine and share the results, we could gain an insight into what’s happening to … Read more
A couple of things make floor slower than a cast and prevent vectorization. The most important one: floor can modify the global state. If you pass a value that is too huge to be represented as an integer in float format, the errno variable gets set to EDOM. Special handling for NaNs is done as … Read more
EDIT: As pointed out in https://stackoverflow.com/a/54053514/2279059, this driver is only needed for the Android virtual device. If you don’t need it (it is useful for debugging, etc.), just see that other answer about how to disable the virtual device in the installer. This workaround did it for me on a relatively fresh Windows 10 PC: … Read more
EDIT: Problem solved. I have to shout out a huge Sorry to the community and a big thank you for your hints. Sorry to user anonymous, who seems to be involved into kernel development. What happened? We spent another 2 days debugging and fiddling around with the program code. No implementation problems were found. BUT: … Read more
MASM (Microsoft Assembler) is the popular assembler for Windows. MASM is for 16-bit and 32-bit applications(x86). ML64 is the one for 64 bit sources (AMD64/x86-64) NASM (Netwide Assembler) is the popular assembler for Linux but is available on Windows too. NASM supports 16-bit, 32 bit and 64 bit programs. FASM (Flat Assembler) is available for … Read more