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Thread: socket 5 and socket 7

  1. #1
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    socket 5 and socket 7

    hi all:

    i have a small question: i am upgrading my friends PC and she has a pentium 133 CPU on a socket 5. i have an old PC with pentium 200 MMX on socket 7. can the 200 MMX work on the socket 5?? i tried it and it physically fits with ZIF but will it actually work???? thanks.........

  2. #2
    Ultimate Member deadkenny's Avatar
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    No, there will not be proper voltage support for an MMX chip on a socket 5 board.

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    Stark Raving MOD Midknyte's Avatar
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    I concur. The bios of the board probably wouldn't support the mmx cpu anyways.

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    Well if the electrical bits and pieces aren't there, why should it? Socket-5 and early socket-7 indeed didn't have "split rail" CPU voltage supply for MMX Pentiums, Cyrix MII, K6 and such.

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    Ultimate Member Rugor's Avatar
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    It won't work, sorry.

    The socket 5 is a 320 pin socket with a plug where the 321st pin would be. The socket 7 cpu is of course a 321 pin design. You may be able to get it into the socket, but it won't work.
    "Dude you're getting a Dell." Obscure curse from the early 21st Century, ascribed to a minor demon-spirit known as "Stephen?" [sp].

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    Ultimate Member deadkenny's Avatar
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    Originally posted by Rugor
    It won't work, sorry.

    The socket 5 is a 320 pin socket with a plug where the 321st pin would be. The socket 7 cpu is of course a 321 pin design. You may be able to get it into the socket, but it won't work.
    That's interesting. It was my understanding also that there's an extra pin on socket 7. But I would have though that the extra pin was there to prevent later CPU's from being inserted into socket 5 boards. In this case though he said it physically fits. In any case, it probably won't work at all because of the extra pin. As Peter mentioned, there are two 'versions' of socket 7, P54 and P55. Only P55 supports the split rail voltage requirements of the later processors (MMX etc.). Although in that case I believe the later processors will run on an older P54 socket 7. But it will fry them eventually, because the vcore will be 3.3v whereas the MMX spec is 2.8v.

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    They won't even work, because not only had the voltage gone down, but also did the amperage go up. Big time.
    And they'll fry in an instant, of course. Just a matter of whether the CPU or the board's voltage regulators go boom first.

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    Go to powerleap.com. They have an adaptor that will allow you to plug a socket 7 CPU into a socket 5 board with correct voltage step-down, etc. The have them available with CPUs of up to 400MHz.

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    ... with which you still need BIOS support. As I said further above, finding that a mainboard BIOS supports a CPU that electrically can't work on that very mainboard is highly unlikely. BIOS engineers have better things to do than implement useless stuff.

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    The BIOS only needs to provice the correct multipliers, etc. The voltage step-down process is transparent.

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    No, sorry. If the BIOS doesn't know what to do with a certain CPU make and model, the thing won't get far. It's the BIOS that initializes the CPU, ya know. (The multipliers are done inside the CPU btw, it has always been that way. The jumpers just let you feed a configuration number.)

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    Ultimate Member deadkenny's Avatar
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    There's an article on Tom's Hardware about running a K6-2 on a socket 5 board using such an adapter, so it can work. I've actually run a P55 Pentium processor on a P54 socket 7 board. The processor heated up pretty fast, but it booted. I'm sure that the processor would have fried eventually. A guy I know claims to have run such a setup for a year before frying the processor.

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    It is my understanding that the CPU does dictate the multiplier; however the BIOS can override and manipulate this. The CPU interprets a signal ? from the motherboard and then sets it accordingly... kind of like the 2x->6x for the K6 series...

    If the motherboard's maximum multiplier is below the CPU's default multiplier, then the CPU dictates without influence, right?

    True, if the BIOS doesn't even know a CPU is there, with the correct pin maps etc, then it wouldn't POST, but the adaptor apparently sets this right -- it has a miniature VRM on it, and if I remember correctly, DIP switches for the core voltage.

    Sorry if I was a bit sharp there, Peter.

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    Sorry, no, it doesn't do that. At all. It's all CPU internal. The association of jumper settings to resulting multipliers is too. E.g. that 2x->6x "remap" is a CPU internal change, the jumper setting that used to mean 2x means 6x for newer K6-2, that's all. CPUs have had different interpretations of the same jumpers for ages - remember K5 (1.5x, 1.75x, 2.0x), Pentium (1.5x-3.0x), Pentium-MMX (2.0x-3.5x), Cyrix 6x86 (1.0x-4.0x)? It's all CPU internal.

    What BIOS does is initialize the CPU's internal configuration registers. And for this, it needs to know what a certain CPU make and model is like. If it doesn't, it can't set the CPU up properly, and the system won't POST right - with caches disabled and all performance features not activated, typically, but some BIOSes choose to halt the system with an unknown CPU in.

    (Hint: Before you even think of trying to teach me more about how you think these things work, please look at my profile )

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    Ultimate Member deadkenny's Avatar
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    Two points:

    First, the CPU 'controling' the multiplier was a change that came in with the later Pentiums. I'm pretty sure up through the early Pentiums the processor would actually run at whatever the mobo FSB / multiplier jumper settings dictated.

    Seond, although the processor does have to be 'recognized' by the BIOS to some extent, this is a pretty generic recognition. Often K6-2 processors will actually run on old socket 7 boards that were never intended to run such processors. Then voltage support becomes the key issue. But it's even possible to run these processors without the proper voltage support. The K6-2's have vcore requirements between 2 and 3 volts, with many socket 7 boards delivering only 2.8v. But often the K6-2 will run at the incorrect voltage, and can even survive quite a while if cooling is properly addressed. I read an article testing a Tualatin adapter product, where a Tualatin Celeron was run on an old slot 1 board using both a slocket and the socket adapter. The CPU was recognized as a 1.4GHz PII but it did run and even produced benchmarks in line with what you would expect from such a chip.

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