what bits? 32/64/128/256?

By conradguerrero ยท 4 replies
Dec 17, 2002
  1. in reference to threads likethis, what is the deal with cpu and gpu technology data?

    Cpu's are only next year comming out with 64bit processors, but gpu's had 128bit processors back in 1999. what's the difference?

  2. Vehementi

    Vehementi TechSpot Paladin Posts: 2,704

    I may be wrong, but this is my take on the bit system:

    A bit is one of the smallest measures of file size in the computer industry. Most internet connections are measured in kilobit- 1,000 bits. Such as 28.8k. You should notice that you don't actually download at 28.8 kilobytes, as downloaders measure, but rather 3.6 kilobytes, which is the equivalent of 28.8 kilbits. A byte is 8 bits, and 28.8 divided by 8 is 3.6. To measure a bit, it is one normal character, i.e. not ASCII, be it a number, letter, sign, etc. A byte is an 8 letter word.
    But, in relation to computer processors, I think the default '32-bit' architecture partains to how much information is calculated on every clock cycle, either 32 or 64 bits at once.* An operating system also runs with this architecture, which is why you hear about the 64-bit version of Windows XP. 64-bit architecture is backwards compatible with 32-bit, but 32 bit cannot run any 64-bit optimized architecture.
    As for the 128-bit GPUs, I think you may be out of context, but I really can't explain that.

    I think I butchered that. I never really learned about the bit architecture system, and these are all just logical assumptions. I would gladly enjoy someone who would explain it to me better/correctly ;)

    *I'm really not sure about that.
  3. Justin

    Justin TS Rookie Posts: 942

    Actually, the pentium and above are interally 64bit. They only communicate to the memory bus at 32bit. (well if you want to get really technical you have two seperate 32bit devices communicating at an effective 64bit)

    And "32bit" or "64bit" can be quite misleading even on the same processor! Many cpus have 32- and 64- bit components, and some olders have 32- and 16-.

    However, in the general term, the "Bit amount" of a particular CPU is directly referring to its communication speed with the motherboard and its addressing capability.

    For instance, the 386, 486, pentium and above can interally address up to 2^32 bits of data, which = 4 gigabytes of addressing. The 286, on the other hand, which was a 24bit cpu in that one aspect could interally address only 2^24 = 16mb of addressable memory. Historical note: the 286 was the first micorprocessor ever created that could address more then 1mb of memory.

    Now here's where it gets even more complicated.

    "Memory" Bit - Memory bitrate is the amount of data that can be transferred (read/written) to or from memory, to that particular device. So although you have "128bit" graphics chips, all that means is that they support 128bit transfers to/from their onboard memory - NOT that they are capable of transferring data to/from the system bus at that speed. Even the fastest video card currently in AGP 8x mode is still limited to the AGP bus 32bit data transfer rate.

    Lastly, the other big one used in system bus bits. Currently, no motherboard or chipset released in the mainstream market is 64bit, it is still all 32bit.(exception: PCI 2.0 and VLB 2.0) That's been true since the 386 era. The 386 SX interally was a 32bit cpu, but could transfer data to/from the system bus at only 16bit.

    As you can see its really not a black-and-white subject; but one that is fascinating if you are into that sort of thing.
  4. Ayasha

    Ayasha TS Rookie Posts: 37


    Just a note to Havesters lengthy explanation. The 386SX internally was a 16-bit processor. The first 32-bit processor was the 386DX. Some Motherboards of the era included a math co-processor socket in which you could give your 386SX, DX like performance. Oh, and pentium and above acctually aren't 64-bit internally they handle 2^32-bit instructions as noted below. At the time they couldn't get a processor to handle a 64-bit string.

  5. Justin

    Justin TS Rookie Posts: 942

    Re: .

    I am fairly certain that the 386SX was internally 32bit and externally 16bit. The "SX" merely implied a lack of an onboard FPU (math co-processor).

    Also, the pentium WAS 64bit internally in that it could communicate to itself at 64bit(by using two seperate 32bit buses), not that it would process 64bit code. It merely made for faster execution / more efficient execution.

    Oh, and I promise you, no processor on earth can handle "2^32-bit" instructions ;)
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