Is Core Duo 64-Bit?

Discussion in 'Mac Blog Discussion' started by MacRumors, Feb 12, 2006.

  1. macrumors bot

    MacRumors

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    Hexus.net vaguely claimed that Intel's Core duo may have support for 64-bit processing. The report is poorly written so is difficult to gather much from it, however, several Mac websites have started reporting it, so it is now linked here for interest sake. It appears that even if the Core Duo had hidden 64-bit capabilities, it is not active on shipping models, making the point somewhat moot.

    It appears the basis of this rumor is that Intel's upcoming Sossaman processor is 64-bit, however, a recent press release specifically notes that Sossaman is a 32-bit processor.

     
  2. macrumors member

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    #2
    what would be the point of hiding these capabilities?
     
  3. macrumors regular

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    #3
    Exactly... would be good but sounds weird
     
  4. macrumors regular

    ScottB

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    #4
    Would raise a few questions if true, that's for sure.
     
  5. macrumors 603

    SiliconAddict

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    #5

    It wasn't ready so instead of either pushing back the chip to a later release date or releasing a buggy chip they disabled the feature on chip. Or at least that is my guess. *shrugs*

    PS- Someone might want to edit the title. I'm not a grammar Nazi or anything but "Is Core Duo is 64-Bit?" Sounds like someone hasn't had their 3AM caffeine fix. :)
     
  6. macrumors 6502

    qubex

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    #6
    Intel "hid" the 64-bit EM64T extensions to the Pentium4 for quite some time, mainly because they weren't yet ready for prime-time. It makes sense for them to integrate the capabilities into chips for testing and evaluation purposes prior to "rolling out" the feature officially.
     
  7. macrumors 68040

    ezekielrage_99

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    #7
    Kind of getting a flashback to 1999 when the Intel Celeron 300A and 400A chips were released rathery quickly.

    The Celeron 300A and Celeron 400A could be clocked higher than most of the Pentium chips at the time, plus they had a whole heap of other cool little specs on the Processor which Intel didn't count on too many users knowing about.

    I think the Duo and Solo has been rushed to be released and there will be quite a few nice little surprises found on both processors which Intel hasn't thought that users might find. The 64 Bit thing kind of makes sense because thats the way the industry in heading.

    Only time will tell ;)
     
  8. macrumors 604

    thejadedmonkey

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  9. macrumors 6502

    qubex

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    #9
    Hmm.

    Both the iMac and MacBook Pro are physically limited to 2 GB of RAM, so even if the processors support 64-bit addressing, it doesn't make much difference. (64-bit arithmetic isn't very useful in everyday usage.)
     
  10. macrumors regular

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    #10
    Wouldn't 64 bit arithmetic be useful for gaming, playing videos, manipulating video data (Shake, Final Cut Pro, Ripping DVDs, Maya) or even photoshop, even handling the GUI candy, just asking, basically anything that's going to be processor intensive.
     
  11. macrumors regular

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    #11
    wait wait wait wait wait wait... hold the Fu-kuck up, if the new "core" chips are 32 bit processors, wouldn't that technically make them the same speed as the G5? (with the G5 having 64 bit omptimized OS and benchmarking) And thereby making Apple's Claim of the new chips being faster moot?
     
  12. macrumors newbie

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    #12
    64-bit are for address space,not arithmetic

    64-Bit means there are "64-bits" of address space. All modern processors can perform 64-bit arithmetic, even "32-bit" processors. Typically, 32-bit processors have a maximum of 2GB of addressable memory (or 4GB on some systems). All a 64-bit processor gets you is more addressable memory, beyond the 2GB limit. Some of the new Intel and AMD 64-bit processors also have more registers, which is helpful, but it really doesn't have anything to do with 64-bit address capability.

    I agree that for video processing, it may be useful to have 64-bits of address space, but the application must be compiled for 64-bit as well. If you really have that much data to crunch through, you're also going to need a huge amount of processing power. This is where a quad G5 makes sense with 8-16GB of memory and 64-bit processors have a role.
     
  13. macrumors G3

    bigandy

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    #13
    hmm, interesting :rolleyes:
     
  14. macrumors 65816

    idea_hamster

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    #14
    Technically, I think that both the iMac and MacBook pro are physically limited to two RAM modules rather than 2GB.

    With the largest modules currently offering only 2GB a piece (available for PMac), this could be a 4GB limit. That still doesn't make a difference, since a 32-bit register can address 4GB of RAM.

    However, this will change in the future and who's to say it won't happen before these iMacs and MacBooks get retired?
     
  15. macrumors regular

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    #15
    Ifthe core duo IS 64-bit, shouldn't that mean it will run XP? (XP-64 supports EFI doesn't it?
     
  16. macrumors 68000

    steve_hill4

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    #16
    I think the maximum you can get into a single slot is 1GB with 32-bit processors. The maximum that consumer computers can handle is 4GB, but spread across four ram slots. I amy be wrong, (as there would currently be no need for so many 2GB sticks of ram), but that's what I recall.

    If you actually check the tech specs of both Core Duo offerings from Apple, they both state a maximum of 2GB in total anyway.
     
  17. macrumors member

    hdasmith

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    #17
    32-bit processors require more than twice the number of cycles and registers to perform 64-bit processing, therefore with larger equations, a 64-bit processor will easily outperform a 32-bit. This is part of the reason the G5's have less cache than the G4's.

    32-bit processors can handle up to 4GB of RAM (2^32 B), 64-bit will handle 18*10^9 GB of RAM (2^64 B), if there was a motherboard that could also handle it.

    Aqua, Quartz, core image, core video, etc. (slight assumption that they have been written for 64-bit processors along with Tiger) really gain from the extra maths capabilities a 64-bit processor has to offer (put the top G4 next to a 1.6GHz G5, and you'll see a difference in Finder).
     
  18. macrumors member

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    #18
    Unfortunatly not...

    So here's the deal guys. Even though there is little doubt in my mind that the core actually does have the 64-bit and VT extensions, Intel is very good about disabling them in the hardware itself. When they actually package the die, they are able to internally bridge various configuration jumpers (no pencil mods here :( ) Below is the actual sysctl output for the new Duo CPU on a iMac Duo:

    machdep.cpu.vendor: GenuineIntel
    machdep.cpu.brand_string: Genuine Intel(R) CPU 1400 @ 1.83GHz
    machdep.cpu.model_string: Unknown Intel P6 Family
    machdep.cpu.family: 6
    machdep.cpu.model: 14
    machdep.cpu.extmodel: 0
    machdep.cpu.extfamily: 0
    machdep.cpu.feature_bits: -1075184641 49577
    machdep.cpu.extfeature_bits: 1048576 0
    machdep.cpu.stepping: 8
    machdep.cpu.signature: 1768
    machdep.cpu.brand: 0
    machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP
    MTRR PGE MCA CMOV PAT CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM SSE3 MON VMX EST TM2 TPR
    machdep.cpu.extfeatures: XD
    machdep.cpu.logical_per_package: 2
    machdep.cpu.cores_per_package: 2

    The fact is that Intel could trivially enable these extensions, and they will. They will sell those chips under a different name for way more money though :D That's awfully clever of them, don't you think? Yeah, it's sad that all that potential is wasted. On bit of hopeful news though, when 64 bit and Virtual Machine support becomes a factor (say when Apple transitions the xServe to x86) there will be little stopping you from slapping in the faster/64bit enabled CPU's as they are not currently soldered to the motherboard.

    Bakafish
     
  19. macrumors G5

    gnasher729

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    #19
    64 bit addressing is actually quite useful.

    For example, many operating systems allow reading and writing of files on your harddisk through "memory mapping": A file is mapped to an area of memory, a program can manipulate the data in the file as if it was in memory. Instead of calling operating system functions to read and write data from the file, this is handled by virtual memory. The problem is: On a 32 bit system, the total size of all everything including memory mapped files must be less than 4 GB. There is no way that a ten GB digital video file could be memory mapped. On a 64 bit OS, no problem.

    Also important: In 64 bit mode, Intel and AMD processors have 16 general purpose register and sixteen floating point/vector registers instead of 8.
     
  20. macrumors 65816

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    #20
    Not neccessarily. More bits isn't always better. First, for many applications like you mentioned (games, 3d modelling, etc) floating point operations are more useful.

    In the Intel world, when they moved from 16-bit to 32-bit it was a big deal, mostly for the change from a segment-offset memory model to a flat 32-bit memory model. Here the ability to get access to > 4gb memory is the big deal, and they've been able to put in some hacks/shortcuts to work around this for several years.

    Just to illustrate how 64-bit isn't always better, let's imagine doing an add for two 32-bit integers with the same values at the assembly (register) level:

    00000000000000000000000000000001 +
    00000000000000000000000000000010

    versus 64-bit:

    0000000000000000000000000000000000000000000000000000000000000001 +
    0000000000000000000000000000000000000000000000000000000000000010

    For this simple add, the 64-bit int is more work and doesn't yield any benefit.

    Microsoft learned this lesson with Windows 95. Remember, they started with 16-bit Windows 3.1 and added 32-bit extensions to it. But the fact was that in many cases the 16-bit code was faster (partly due to years of optimization) so key parts of Windows 95's subsystem stayed 16-bit internally and used 32-bit thunking to talk to their 32-bit "other halves".
     
  21. macrumors member

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    #21
    I should have been more clear.

    That output I showed above clearly indicates that 64 bit and all of the new Virtual thread / Virtual machine extensions are disabled on these chips. So this is a non-story from a technical aspect.
     
  22. macrumors 601

    Anonymous Freak

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    #22
    Sossaman not 32-bit, so neither is Yonah.

    No.

    http://www.intel.com/pressroom/kits/events/idffall_2005/20050824gelsinger.pdf
    http://www.supermicro.com/newsroom/pressreleases/2006/press020706.cfm

    I trust the VP in charge of Intel's CPU division, and an official Press Release from a major Intel server motherboard producer a LOT more than a random rumor on Gizmodo, or a blog of unknown origin.

    If you follow all of the 'proof' links out there, they all lead back to the same Hexus.net source. (Gizmodo and your blog both point to the same Hexus source, so they're not two sources, only one.) (And in all of The Register's info on Sossaman, even they never once mention 64-bit.)

    I don't even know where Gizmodo got their info, as they say that "Intel openly admits that its Sossaman chips are 64-bit..." but there has been no such admission, and Hexus is their stated source. But Hexus just says "And it transpires that Sossaman supports iAMD64..." With no sourcing of any kind.

    The Register reports "Sossaman takes Yonah and adds dual-processor support, along with a 36-bit physical address bus to allow the chip to handle up to 64GB of physical memory..." I'm guessing someone saw 'non-32-bit', and '64 GB', and inferred 64-bit, which is wrong. It's a 32-bit chip, which processes data in 32-bit chunks, that happens to have a 36-bit memory address space. (In fact, the original Pentium II Xeon could address 36-bits of memory, so this isn't even new to the P6 line, of which Yonah and Sossaman are a part of.)
     
  23. macrumors 65816

    idea_hamster

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    #23
    Hmmm. Perhaps, but the tech specs of the Quad PowerMac says it has a 16GB RAM limit, when we know that it is much more. Theoretically it is 2^64 or 16 exabytes, but in practice I recall that RAM is handled by a 43-bit register, so currently it could only address 2^43 or 8.8 terabytes.

    I'd be interested to see an explanation of why there is a 1GB-per-module limit associated with 32-bit processors -- but my suspicion is that this is really about what is commercially available. I don't ever recall hearing that there is something about the slot that limits the RAM amount.

    When Apple says that a computer has a "max RAM amount," it really means that this is the most RAM that you can get installed through them. Since they only sell 1GB modules for the Core Duo Macs and each has two slots, the official Apple math is simple -- a max of 2GB.

    Of course, without the expansion slots, it's all just hot air.... :)
     
  24. macrumors member

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    #24
    Money.

    Intel do this all the time. They have two (or more) products all based on the
    same processor core. However they cripple one so that it can sell at a competitive price while leaving the uncrippled version at full-price.

    There really isn't much difference between Celeron,P4 and Xeon... howver intel can charge alot more for the xeon's and P4's because the Celerons are lame.

    So, Intel will sell Core Duo (Yonar) for one price and an identical (or near idential) chip as a Xeon at a much higher price.

    As a side note, The Sossaman based CPU's would seem an obvious choise for XServes. Anyone want to start a rumor about when the "iServe" will ship?
     
  25. macrumors 68040

    shamino

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    #25
    64-bit does not mean "faster". It's just a marketing term to mean some key parts of the chip (typically address busses and general-purpose registers) are 64-bits wide.

    As others have already said, this doesn't mean very much for most programs. If your application has no need for more than 4G of RAM or wide registers, 64-bit code can actually run slower than 32-bit code (because memory pointers are larger, meaning apps use more memory and consume more cache.)

    The reasoon 64-bit chips historically run faster than 32-bit chips is because they usually have higher clock speeds, faster busses, or larger caches. Applying those same factors to a 32-bit chip will speed them up just as much.

    Taking a CoreDuo and flipping some internal bit to activate 64-bit features will not speed it up. It will have the same size and speed cache. It will have the same bus. It will have the same clocking.

    This might be useful if you have some application that requires a 64-bit processor (like some Photoshop plugins that can take advantage of huge memory sizes), but that won't mean anything to an iMac owner, since the hardware can't support more than 2G of RAM anyway.
     

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