Which is faster ? K6-2 550 or K6-3 450 ?

[aberant]

K6-3 has onboard L2 cache, K6-2 doesn't but has extra 100mhz. Any thoughts ? Thanks a lot

 

[ProviaFan]

It depends. I suppose SETI would like the L2, but if there's not enough L2 to hold all of the core SETI kernel (and I doubt there is), then you may not see much advantage. Also, I heard that ECC? projects are a good deal faster on K6-3s than K6-2s, regardless of MHz.

If it's possible, you could try both, and see which is better.

 

[ken008]

Might depend on the board a little also. 1 meg L3 or L2 depending may make a difference. I think some boards have 2 meg L2 or L3. And some only have 512k. The K6-3 has tri-level cache, the cache on the motherboard may make a difference. I know when they were popular a 1 meg onboard cache was desirable.

 

[jjmIII]

I strongly believe the onchip L2 will outweigh. I've had both chips.....something I'm not proud of, LOL.

 

[Petro89]

My second system is a K6-3 450, and just a few weeks ago I was playing around with a K6-2 550. The Windows performance just seems much snappier with the K6-3. CPUMark scores were 45ish for the K6-3, and 35-ish for the K6-2. 3Dmark2001SE was 1220 with the K6-3, and 1150 with the K6-2 (that's with a geforce2 GTS). UT and Q3 FPS were about 2-3 FPS better with the K6-3.

Performance was thus very close, but the K6-3 managed to edge the K6-2 out across the board.

K6-2s were good up to about 400 Mhz or so. Above that, the lack of L2 cache really hurt. It still uses the motherboard cache as L2, and that only runs at 100 Mhz (or whatever your board's FSB is). So it is like this...

K6-3 450, 450Mhz, L2 onboard runs at full speed=450 Mhz, L3 is motherboard cache=100Mhz
K6-2 550, 550Mhz, L2 is motherboard cache=100Mhz

As the K6-2 goes up in speed, it becomes more and more starved for cache, and the performance gains are very minimal.

Good luck!

 

[BobTheWizard]

hey... the K6-II and the K6-III weren't bad chips for their time.... I still have a system (missing Floppy and CDRom) with a K6-III 450. It was my primary system until a couple of months ago, when I upgraded to my current system. I plan to get that one up soon... might do Linux with it, just to learn, and check out Linux.

I think the K6-III is going to be a little faster, but not so much that you could really tell the difference. It might be a good test to see which would do the WUs faster....hmmm... thinking I still have that K6-II 500 chip around somewhere... just have to find a good, cheap mobo for it...

 

[aberant]

cool, thanks guys. I can't get both to test cos i don't have access to either - i'll be buying one or the other off ebay. The consensus seems to be get the K6-3 and overclock it to 550 odd, which might well be do-able, might even get 600. Just to add to the confusion thought, i think this board might allow me to run a K6-2+ / K6-3+ , both of which have onboard L2 among another few bits. So now there's 3 choices - K6-2 550, K6-3 450 or K6-3+ 550 this is hard

 

[BurntKooshie]

The other guys seem to have hit the highpoints.

A recap: without on-die L2 cache, increasing the processor frequency doesn't do much, because of the disparity between bandwidth required by the CPU, and bandwidth afforded by whatever L2 is available.

Now, a common misconception: It's not the frequency of the L2 cache that's most important, it's how does the bandwidth scale in comparison to the CPU core, and how does the latency of a L2 access compare when increasing the core frequency. Frequency increases just happens to make the bandwidth scale.

With the K6-2, the bandwidth stays the same (ie, the ratio of core-bandwidth requirments to L2 cache bandwidth afforded increases). The latencies also increase. What takes, say, 20 cycles, for a L2 hit on a 500mhz K6-2, takes MORE THAN 20 cycles from the perspective of, say, a 600mhz K6-2 (I don't even recall if such a chip exists).

With the K6-III, the bandwidth of the L2 goes up, because the frequency goes up. The latencies stay the same, also because the frequency goes up, and because AMD didn't do any funny business with that.

The K6-2+ and K6-III+ are slightly different beasts.

The K6-2+ has 128Kb L2 cache. Given that it has 64Kb L1 cache, and it's NOT an exclusive architecture, this is more or less 64Kb of useful L2 cache (it's not exact, because, though I know it's NOT exclusive, I can't say for sure off the top of my head if it's a strictly includive architecture).

The K6-III+ has the exact same cache structure as the K6-III.

However, as people here probably know, Intel just cuts the L2 cache in half ( or less, depending... ) to create a Celeron. AMD doesn't do that with the K6-2+ from the K6-III+. They are two physically different chips, just as the Athlon and Duron were/are two physically different chips. This means that the L2 associativity of the L2 on a K6-2+ is NOT cut in half (or less ) like it is on Celerons.

The only other major additions that have any meaning to anyone here would be the Extended 3dNow! instructions (the ones that were added to the original Athlon over the K6-2 and K6-III that had the original 3dNo1! instructions).

Um.......okay, so what's this boil down to? If you are POSITIVE that your motherboard either does, or can (via a bios update) support the K6-III+, go for that over the other ones. Go for a K6-III over a K6-2 and K6-2+ (it'll be a tough call if you can get a 550mhz K6-2+ vs. a 450mhz K6-III ). Go for a K6-2+ over a K6-2.

Oh yeah

/me waves to aberant.

 

[compudog]

K6/3-450 is faster than a K6/2-550. The plus versions were primarily designed for the mobile market and include (among some other improvements) AMD's "PowerNow!" (or something like that) technology. I definately agree with BurntKooshie's suggestion.

 

[aberant]

righto, was up on most of that and u've pretty much mirrored my thoughts, the only thing remaining now then is whether to get the K6-3 or K6-3+. and that seems to have been answered for me in that i've never seen one for sale, so K6-3 it is as for the mobo support, when they released the board it claimed support for the chips, but then AMD must have had a word in Tyan's ear, cos they then said that the board didn't support it contrary to what it says on the box, cos it's a mobile solution. SO, there's no way of knowing if they removed the support for it from BIOS or not in the newest image. Guess i can't afford to take that risk. So thanks a lot for the info, mobo/chip/ram on its way along with my first desktop install of linux wish me luck !

PS Hey BK ! I thought u'd left us ! nice to see u again matey, keep in touch