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Comments:
<0> yo
<1> I'm using the LC-3 instruction set, I'm trying to optimize my code. Lets say the PC contains x3010 and the following memory locations contain the values: x3050 -> x70A4, x70A2 -> x70A3, x70A3 -> xFFFF, x70A4 -> x123B.
<1> <1> Then I have the following LC-3 instructions x3010: 1110 1100 0011 1111, x3011: 0110 1000 1100 0000, x3012: 0110 1101 0000 0000
<1> <1> What single instruction could replace the above three?
<2> You're going to have to give us the backstory on that one
<1> well
<1> 1110 is the opcode for LEA
<1> so, 1110 1100 0011 1111, is LEA R6 <- PC + x003F
<1> so in the register R6 is being set w/ the memory value of x3011 + x30FF = x3050
<1> thats the first instruction
<2> Unfortunately, I don't think any of us are familiar with that instruction set
<1> well ignore the instruction set
<1> the asm is similar
<1> 0110 1000 1100 0000 would be LDR: R4 <- R3 + 00000 (i.e- base+offset)
<2> Give us the three instruction with detailed descriptions of what they do in conjuction
<1> LEA = load effective address, computes address of PC + signed offset and stores result into a register
<1> first four bits is the opcode, next three bits is destination register, and last 9 bits is PCOffset
<1> so 1100 110 000111111 would be: LEA R6 PC+x003F
<1> next two instructions
<1> use the 0110, use the LDR instruction
<1> Load into register using Base+Offset
<3> always 32-bit opcodes?
<1> addressing mode
<1> no
<1> 16 bits
<3> err yeah, my bad
<1> the 6-bit offset is literally taken from the instruction, bits [5 to 0]. The base register is specified by bits [8 to 6] of the instruction
<1> so the address of the operand is obtained by adding a sign-extended 6-bit offset to a base register
<1> in this case, 0110 100 011 000000, LDR: R4 <- R3 + 00000 (i.e- base register + offset)
<1> oh in the instruction before, the PC is automatically incremented simultaneously at the same time the instruction is executed
<1> so first instruction was at hex x3010
<1> so PC is actually pointing to next instruction
<1> at x3011
<2> I think you're on your own, jojo
<1> so, 1110 1100 0011 1111, is LEA R6 <- PC + x003F , would be x3011+ x003F = x3050
<1> anyhow
<1> the last instruction
<1> 0110 110 100 000000, LDR: R6 <- R4 + 00000
<1> with the following memory locations containing the values: x3050 -> x70A4, x70A2 -> x70A3, x70A3 -> xFFFF, x70A4 -> x123B, already. what could i replace the above three instructions with a single instruction
<2> No idea.
<1> would i be able to replace all three with an instruction using indirect addressing mode?
<2> No idea.
<2> It's all meaningless to me
<2> Why do you care what the memory locations have?
<1> ie. - instead of the address *being* the address of the operand to be loaded, instead it *contains* the address of the operand to be loaded
<1> i don't
<1> its just an example
<1> of trying to optmize some code
<1> anyhow, a value is loaded into register R6 using the above three instructions, i want to find out, instead of doing three instructions, minimize it to a single instruction
<2> Probably.. but I'm not familiar enough with the instruction set (nor exactly what you're doing) to be able to tell you what.
<1> not really doing anything
<1> just moving stuff around
<1> from memory to registers
<1> using different addressing modes
<1> namely, immediate mode and base+offset
<1> here's something i found on it: http://cs.gmu.edu/~setia/cs367/slides/lecture3.pdf
<1> it's giving me a headache... blah =/
<4> then stop worrying about it. :)
<2> Sage advice
<4> Thank you
<1> hehe
<5> Geez. A cl***mate sent me a message: "My only friend... my life ends here. I installed WoW and I'm going to play in an official server. My life ends here."
<1> lol
<2> What is an unofficial server?
<6> a pirate server i'd guess..
<6> i wouldnt think the server code would be released though
<2> It's not
<2> And nobody has the kind of hardware you'd need
<5> TCA: I think they "emulate" a server.
<2> _exe: I seriously doubt that
<6> well if you ran a server with < 20 clients or so you probably wouldnt need much in terms of hardware
<6> i dont know though... ive never played
<1> wouldn't be much fun
<1> :P
<5> Heh, I don't. My friends do that all the time, because it's kinda expensive playing in a official server I think.
<2> They play on an un-official WoW server?
<5> .google WoW emulator linux
<7> Installing WoW Server on Linux - Wickle Wiki, "http://www.wickle.com/wiki/index.php/Installing_WoW_Server_on_Linux";
<7> tow.com blog WWNC 2006, "http://www.tow.com/2006/01/14/wwnc-2006/";
<5> Exactly.
<7> Electronic Recordkeeping > Preservation > Products > Emulators "http://www-personal.si.umich.edu/~calz/ermlinks/prod_emu.htm";
<2> Amazing
<2> although, every link is broken
<2> openwow is toast
<2> wddg is gone
<2> blackstorm is suspended
<2> blizzhackers even forbids you to talk about server emulation
<5> :_/
<6> i wonder if someone reversed the WoW protocol and related or if the source code was leaked
<5> Later I can ask him which server he plays on.
<2> I cannot possibly imagine why you wouldn't pay $15/month if you wanted to play
<5> us$15/month is a lot to a 18yo guy from a third world country.
<2> Right. And the zillions of chinese don't have a problem with it.. why?
<5> I don't have idea. I'm not chinese.
<5> My parents give me us$17/month, and I have to buy everything I need with that.
<5> And I'm not poor.
<2> Fair point
<2> Personally, if I were a parent, I'd be more than happy to pay for an account
<4> I got 100 per month, plus $25 for each As I make each 6 weeksl.. And I was a straight A student with 7 cl***es
<4> :p
<2> Keeps them off the streets and enslaved.
<2> It's one of those things I'd do if I were an evil overlord. 100. Finally, to keep my subjects permanently locked in a mindless trance, I will provide each of them with free unlimited Internet access.
<2> Hellsphreak is our newest star pupil.
<2> Sorry, _exe...
<5> Heh, internet a great mind control tool.
<5> Haha
<5> Where are you from, hellsphreak ?
<4> My mom's uterus, I'm guessing
<2> Well, if you go far enough back your dad's...
<4> Even that is beyond my comprehension. I'll stick with what I can grasp.
<4> :p
<5> Heh, okey.
<4> OK, fine... You win. Texas.
<2> Land of the cow patties
<4> Yadda yadda
<2> Why is New Mexico so windy?
<5> TCA's neighbor.
<4> But it has one thing that your land does not......
<2> Because texas ****s, and arizona blows
<4> ME!
<2> Fair enough
<1> if a machine had an addressabilty of 1 byte (8 bits) and a total memory size of 64K bytes. how many bits would be required in the PC to address all of memory?
<1> 3 bits?
<2> What do you mean by "had an addressability of 1 byte" ?
<4> You just will not give up, eh?
<1> meaning memory has an address space of 2^8
<1> locations that is
<2> Right, well, you'll still need a 16-bit address
<1> well actually addressability would be how many bits per location
<2> If it can only see 256 bytes at a time, then you only need a byte pointer
<2> But you'd need some way to tell you which bank you're looking at.
<2> Otherwise your "total memory size of 64k bytes" is meaningless and you really mean to say "total memory size of 256 bytes"
<1> but if it were 64k bytes of memory, how many bits would i need in the PC to address all of it if required?
<2> 16 bites
<2> 16-bits
<2> Stupid fingers betraying me again
<4> They should betray you in other ways
<4> herslef
<4> herself.....
<4> *headdesk*
<2> hahaha
<4> hush.
<1> if the instruction length were kept at 16-bits
<1> would that post a problem?
<2> Yes, that would be a problem if it was a fixed width instruction set, and they were fixed to 16-bits
<2> Unless you're clever. Like me.
<2> And then you'd just use two instructions. A prefix instruction (next instruction is the address) and then the address
<4> I believe he wants to nib it down to just one instruction.
<4> Now, as to why he wants to do this, is beyond me.
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