8086 Disassembler Download Recipe
Zee Badoni
The Recipe pane is where your chosen Operations are configured. If you are a programmer, think of these as functions. If you are not a programmer, these are like steps in a cake recipe. The Input data will be processed based on the Operations in your Recipe.
The interface is designed with simplicity at its heart. Complex techniques are now as trivial as drag-and-drop. Simple functions can be combined to build up a "recipe", potentially resulting in complex analysis, which can be shared with other users and used with their input.
I tried to look at the disassembly the compiler generated; referred to the Turbo C++ 3.0 manual; refereed to the 8086 to Pentium Assembly Programming text book but couldn't find a solution to this problem.
To examine memory in GDB, you use the x commandwith different arguments. TheGDBmanual has full details. For now, it is enough to know that the recipex/Nx ADDR prints Nwords of memory at ADDR. (Note that both 'x's inthe command are lowercase.)Warning: The size of a word is not a universal standard. In GNU assembly, a word is twobytes (the 'w' in xorw, which stands for word, means 2 bytes).
First open two terminal windows,and run make qemu-gdb in one and gdb in the otherto debug xv6 remotely,as described in the previous homework assignment.This time let's look more closely at GDB's outputimmediately after it connects to the QEMU process running xv6:$ gdbGNU gdb (GDB; openSUSE 11.1) 6.8.50.20081120-cvs...+ target remote localhost:272960x0000fff0 in ?? ()The target architecture is assumed to be i8086[f000:fff0] 0xffff0:ljmp $0xf000,$0xe05b(gdb)The following line is GDB's disassemblyof the first instruction to be executed.[f000:fff0] 0xffff0:ljmp $0xf000,$0xe05bFrom this output you can conclude a few things:
- The IBM PC starts executing at physical address 0x000ffff0,which is at the very top of the 64KB area reserved for the ROM BIOS.
- The PC starts executingwith CS = 0xf000 and IP = 0xfff0.
- The first instruction to be executed is a jmp instruction,which jumps to the segmented addressCS = 0xf000 and IP = 0xe05b.
To examine memory in GDB, you use the x commandwith different arguments. TheGDB manualhas full details. For now, it is enough to know that the recipex/Nx ADDR prints Nwords of memory at ADDR. (Note that both 'x's inthe command are lowercase.)
Today is the second hot day in a row so my mind starts to think grilling season is really here even though we do grill in cold weather sometimes. I never knew what brown sugar really was. This recipe does look good and skewers are a good way to grill.
Wow what a cool way to use that as a skewer! Great presentation! I love how this recipe sounds so full of flavor! It reminds me of how my mom does her BBQ pork! I love that so I know I will love this!
Why then does the 8088 exist, and why has it become so popular? An 8-bit-bus version of the 8086 (that is, the 8088) was desirable in the late 1970s because at that time it was significantly more expensive to build a computer with a 16-bit data bus than with an 8-bit data bus. The 8088 allowed the construction of low-cost, low-performance computers that would run 8086 software, albeit more slowly. As it turned out, the cost advantage of an 8-bit memory data bus quickly became relatively insignificant, and the 8088 might have vanished into obscurity had IBM not selected it for the PC; then we might never have had the pleasure of wrestling with the prefetch queue cycle-eater. However, IBM did select the 8088 for the PC, and the rest is history.
The upshot of all this is simply that the 8088 can transfer word-sized data to and from memory at only half the speed of the 8086, which inevitably causes performance problems when coupled with an Execution Unit that can process word-sized data every bit as fast as an 8086. These problems show up with any code that uses word-sized memory operands. More ominously, as we will see shortly, the 8-bit bus cycle-eater can cause performance problems with other sorts of code as well.
I read that and was slightly confused. Duplicating functionality like that seems wasteful and a recipe for problems even, and I wondered why not just use USB-connected 2.5Gbps ethernet (USB has enough bandwidth), but I guess this might boil down to hardware availability (PCIe allows using any existing PCIe ethernet chip), and/or bandwidth considerations (PCIe might be more efficient, and does not share bandwidth with other USB devices).
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