Pentium 1 motherboard questions.

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Reply 20 of 20, by Tetrium

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dionb wrote on 2020-10-18, 13:40:
Tetrium wrote on 2020-10-18, 11:35:
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Most Pentium MMX CPUs are actually not multiplier locked. At one time I tested virtually all my Pentium MMX CPUs 166MHz and 200MHz and only the later ones had only (some of) their higher multipliers locked.
What do you mean with translated multipliers? I assume you mean that a CPU will seem to interpret a certain multiplier for a different multiplier? If so, then this is caused by some of the multiplier settings having been disabled on the CPU so the motherboard settings for that BF pin doesn't affect the multiplier anymore (which is basically how they locked the higher multiplier afaik).
Iiuc it's mostly the Overdrive chips that are locked, but I'm not 100% certain about that.

Translated multiplier: P55C (Pentium MMX) interprets 1.5x (BF0 and BF1 both high) as 3.5x. So you can't set one of these CPUs to lower than 2x (BF0 low, BF1 high) whatever bus you are running.

K6-2 CXT core does the same with 2x, interpreting it as 6x, so the lowest multiplier you can set there is 2.5x (BF0 and BF1 both low, BF2 high/floating)

Oh of course! Yes that makes sense 😜

I've always seen them as basically more, say, being just the 1.5x silkscreened onto the PCB, but the actual jumper setting having different meanings to different CPUs. Since I always seen these CPU multipliers (like PMMX and K6-2) as native to the CPU, I never saw them as having been translated ever, because there was nothing to translate. That is just how these other CPUs are.

The 1.5x multiplier setting is just called that, a jumper setting for the 1.5x multiplier. But now I get what was meant with "translated" 😜

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