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AMD K5 SSA/5 vs 5k86

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First post, by dave343

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I picked up a AMD K5 PR100 today, but I've come to read the original K5 CPU's were not as fast as the later models, due to the fact AMD had the branch prediction unit disabled. What I'm confused about is that AMD re-released the K5 cpu's with the Brand Prediction unit enabled, and re-badged the CPU's to just say K5, and not SSA/5. I think... all 75mhz and 90mhz versions were SSA/5 even if they were re-badged, but does anyone know if the PR100 CPU's always remained SSA/5 or did AMD enable the BP unit and like all faster K5 CPU's, just call it K5. I've searched CPU-World, the Anandtech K5 article, Wikipedia, but the info isn't clear, except to say AMD re-released the CPU's under the K5 naming sceme once they fixed the 2nd round of K5 cpus.
Mine is the AMD K5-PR100ABR. Anandtech says it was re-released as a PR100 (75mhz), but I can't find anything about that anywhere else. Wiki just states that they fixed the K5's and turned on the BP unit starting at PR120 CPU's, but a few other websites say AMD re-released the PR100 CPU too, but the newer version has the BP unit turned on, making it a lot faster.

Reply 1 of 4, by Warlord

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That one is the disabled one. The enabled one is the PR133 which is a rebadged 100. with BP and a gold heat spreader.

the pr 120 amd changed the name so that the name is the equivalent clock rate of a Pentium but it is not the real clock rate of the chip. pr120 is 90 mhz but has branch prediction

pr133 is 100 mhz

your chip is the last PR rating that matches the speed of the chip. there was a refresh of the one you have but they didnt add a BP they just added a gold heat spreader.

http://www.cpu-collection.de/?tn=0&l0=co&l1=A … AMD-K5-PR100ABR

Reply 2 of 4, by dave343

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Warlord wrote:
That one is the disabled one. The enabled one is the PR133 which is a rebadged 100. with BP and a gold heat spreader. […]
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That one is the disabled one. The enabled one is the PR133 which is a rebadged 100. with BP and a gold heat spreader.

the pr 120 amd changed the name so that the name is the equivalent clock rate of a Pentium but it is not the real clock rate of the chip. pr120 is 90 mhz but has branch prediction

pr133 is 100 mhz

your chip is the last PR rating that matches the speed of the chip. there was a refresh of the one you have but they didnt add a BP they just added a gold heat spreader.

http://www.cpu-collection.de/?tn=0&l0=co&l1=A … AMD-K5-PR100ABR

That’s disappointing... but at least I found a K5 finally, grabbed it from RE-PC in Seattle. So obviously it it had the branch prediction unit enabled it would smoke a P100, but how much of a hit is it taking against a P100 as a SSA/5?? Is it equivalent, or more matches a P75/90? I know the PR166 runs at only 116mhz, so if the PR100 runs at 100mhz... that must be a huge hit? Thanks

Reply 3 of 4, by alvaro84

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You may have a look at this thread:
http://www.cpu-world.com/forum/viewtopic.php?t=31230

Here I did (DOS) benchmarks of the two K5 revisions at the same clock speed.

Shame on us, doomed from the start
May God have mercy on our dirty little hearts

Reply 4 of 4, by dave343

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alvaro84 wrote:

You may have a look at this thread:
http://www.cpu-world.com/forum/viewtopic.php?t=31230

Here I did (DOS) benchmarks of the two K5 revisions at the same clock speed.

Thanks, doesn't look too bad.

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