isa

I have a complicated problem, exacerbated by the fact I don't really know where to start! Over the last few years, I've developed a number of php web-based systems. When I built them, our network was ropey at best, so I thought nothing of creating my own username/password stuff. Since then, our network has become a lot more robust, our admins have installed an ISA server for various other things and my apps are left as frustrating relics that people forget their passwords and are never sure which one belongs to what. I would like to be able to replace my own login code with something that will

AFAIK x86-64 adds a number of general purpose registers to those derived from Intel x86 ( rax , rcx , etc), called r8 - r15 . Why did they name the new registers like this? Why not just follow existing naming convention and call them like rfx , rgx ... ? Numbering CPU registers is the norm, almost any processor does that. The 8086 processor however is ancient, they had an extremely limited transistor budget back in 1976. Implementing a 16-bit processor with only 20,000 active transistors was quite a tour-de-force. One way they cut down was by giving registers dedicated functions. At that point

I am trying to add jal functionality to the following but I am stuck with how does it work. I know that it stores the old PC+4 value in the $ra register and then transfers the control to the function which transfers back the control by return $ra but how do I implement it in the hardware? There are two things you need to do. Add a mux at the input of the Registers so that the PC+4 value can be selected as the data to be written. With the appropriate control signal this will allow you to write PC+4 as an additional effect of the "jal $ra" instruction. Implement the return "jr $ra" instruction.

Is there a standard CPAN way of finding out all the superclasses of a Perl class (or better yet entire superclass tree, up to UNIVERSAL)? Or is the best practice to simply examine @{"${$class}::ISA"} for each class, class's parents etc...? There is no "standard way" because this is not a standard thing you want to do. For anything other than visualization it is an OO red flag to want to inspect your inheritance tree. In addition to Class::ISA, there is mro::get_linear_isa() . Both have been in core for a while so they could be considered "standard" for some definition. Both of those show

I am confused about the difference between add and addu. The MIPS instruction reference says: add (with overflow) add unsigned (no overflow) My understanding is to use add with signed operands and addu with unsigned operands. But let's consider this example (with only 6bit): overflow | V 1 | 1 1 1 <- carry | 1 1 1 1 0 1 + | 1 1 1 1 1 0 = ----------------- | 1 1 1 0 1 1 And this is my reasoning: if I consider the first and second operand signed numbers (two's complement), then the result is correct (-3 + -2 = -5) and I don't want an overflow exception. So I would use addu to avoid this