hamish@waikato.ac.nz (03/13/90)
I quote from the official motorola MC68010/MC68012 16-/32 bit Virtual
Memory Microprocessors Advance Information manulal, May 1985.
"Instructions are from one to five words in length...."
pg 2.4
This means that an instruction is anywhere from 2-10 bytes in length,
irrespective of the processor being used, (68008-68030, 020&030 might have
longer ones, but I doubt it.)
Instructions must start on a word boundary, ie every 16 bits. A 32 bit word is
a LONG WORD.
pg 1.3
The length of instruction & the instruction itself are specified in the first
word of the instruction & the others are the instruction operands.
Hope it helps to all involved in possibly misleading statements which have
flown past my screen involved in this subject of memory size.
Remember
1024k bytes = 512k words = 256k long words.
Which also equals 2048 nibbles.
Hamish Marson.bbaker@cbmvax.commodore.com (Bob Baker - Product Assurance) (03/13/90)
In article <223.25fd1cf8@waikato.ac.nz> hamish@waikato.ac.nz writes: > I quote from the official motorola MC68010/MC68012 16-/32 bit Virtual > Memory Microprocessors Advance Information manulal, May 1985. > > "Instructions are from one to five words in length...." > pg 2.4 > > This means that an instruction is anywhere from 2-10 bytes in length, > irrespective of the processor being used, (68008-68030, 020&030 might have > longer ones, but I doubt it.) Actually, if you include the floating point instructions then the maximum instruction length can go up to 8 WORDS (16 bytes) when using immediate operands!
pl@etana.tut.fi (Lehtinen Pertti) (03/14/90)
From article <10136@cbmvax.commodore.com>, by bbaker@cbmvax.commodore.com (Bob Baker - Product Assurance): > In article <223.25fd1cf8@waikato.ac.nz> hamish@waikato.ac.nz writes: >> I quote from the official motorola MC68010/MC68012 16-/32 bit Virtual >> Memory Microprocessors Advance Information manulal, May 1985. >> >> "Instructions are from one to five words in length...." >> pg 2.4 >> >> This means that an instruction is anywhere from 2-10 bytes in length, Actually it means that instructions are 1 to five WORDS in length as odd number of bytes is not allowed. One word is two bytes but it can't be generalized. >> irrespective of the processor being used, (68008-68030, 020&030 might have >> longer ones, but I doubt it.) > > Actually, if you include the floating point instructions then the > maximum instruction length can go up to 8 WORDS (16 bytes) when using > immediate operands! > In 68020 (030/040) move with two memory indexed operands is upto 11 words in length. (opcode + extension + 32 bit disp + 32 bit disp + extension + 32 bit disp + 32 bit disp). -- pl@tut.fi ! All opinions expressed above are Pertti Lehtinen ! purely offending and in subject Tampere University of Technology ! to change without any further Software Systems Laboratory ! notice
hue@netcom.UUCP (Jonathan Hue) (03/15/90)
When I think of instructions, I think of the things that actually have to be decoded by the CPU. That's why I said 1 to 3 words for the '020 and '030. By Motorola's definition, that would be the operation word and one or two special operand specifiers. An "instruction" as defined by Motorola includes those, and any words specifying source and destination effective address, which can be up to five words each. 1+5+5 = 11, as someone pointed out earlier. Others call the operation word the instruction, and therefore say all instructions are one word. All three definitions could be considered correct. -Jonathan