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K6-II 550Mhz vs. K6-III 400Mhz

Posted: Wed Sep 01, 2010 6:09 am
by KenB
I've got an old school gaming system running nice with a 400 K6-III on it (regular K6-III, not "plus" model). Wow, the thing even plays DVD's pretty smoothly, too, using a 3DFX Voodoo3 card and 100Mhz FSB for the RAM. I was never able to get DVD's to play good on K6 machines before, and I believe I had determined a few years ago that it was because most of the Super Socket 7 chipsets available did not have fast enough memory interface. Although this particular VIA VP3 based-board (FIC 2013 board) seems to do the trick.

Was wondering if a regular 550Mhz chip might perform even a little better? I tried overclocking this III unit, and it won't budge much past 400.

Anyone have idea on that?

Posted: Wed Sep 01, 2010 6:54 pm
by AlleyViper
I really wouldn't bet on it. If your MB supports, go to a k6 2+ instead if you can't get a III+, both should be quite cheap now.

Depending on your MB cache, a regular K6 2 will slow down your system too much due to it's maximum cacheable memory cap, which can be limited as some measly 128MB* if you only have 512kb L3 onboard. The on-die L3 cache gets rid of that limit.

*edited

Posted: Thu Sep 02, 2010 1:48 am
by KenB
Mmmm. OK, I didn't think about that. However, my board has 1MB L2 built-in. What is the cacheable limit of a system with 1MB?

Posted: Thu Sep 02, 2010 6:19 am
by AlleyViper
Acording to this post http://www.tomshardware.co.uk/forum/732 ... mhz-advice , it should be 256MB. But still, you should be looking for a cpu with L2 cache instead.

Posted: Thu Sep 02, 2010 8:12 pm
by Jim
Your best bet, though hard to find is a K6-3+ 550 ACR. Second best is a K6-3+ 500 ANZ. Third best is a K6-3+ 450 ACZ. Any of these is quite capeable of clocking 600 MHz (6x100) or slightly higher, though you will get better memory performance using the 5.5 multiplier (5.5x100 = 550 MHz works better than 6x100 = 600 MHz for some reason.) For best results OC the FSB as high as you can get it to run stable when using the 5.5 multiplier.

See : http://www.k6plus.com/index.php?name=PN ... pic&t=1434

Posted: Mon Sep 13, 2010 9:58 am
by jsc1973
You might get a little better DVD playback with a K6-2 550, because DVD playback on a system without SSE is very FPU-dependent, and a K6-2 550 will beat a K6-III 400 in raw FPU performance. The FPU in the two chips is identical.

However, there are several reasons I wouldn't do this:

1. A K6-III 400 blows the doors off any K6-2, even a 550, in all other respects.

2. A K6-2, because of its antiquated cache design, is almost helpless if used on any of today's software, which expects and depends on a fast L2 cache. A K6-2+ or K6-III, while not fast, will still get the job done.

3. The K6-2 550 had a history of unreliability. It was basically a factory overclock. If I see a K6-2 550, the first thing I do is set it back to 500.

4. For very little money, you can buy a K6-2+ CPU now, overclock it to 600 MHz, and get the performance of a K6-III 550, rather than a K6-2 550.

It doesn't surprise me that you were unable to overclock the original K6-III. Those chips ran at their thermal limits, and AMD never got great yields on it. The rare K6-III 333 was a good overclocker, often good for 112*3.5 on a VA-503+, at which speed it was faster than a P2-400 or Celeron 466. But you didn't see many of those parts.

K6 systems are still viable today, but you almost have to have a K6-III, K6-2+ or K6-III+. The three-level cache is what keeps them able to do useful work. In the last several months, I've revived four old Compaq 1200 and 1600 series laptops by replacing their old K6-2 processors with K6-2+ or K6-III+. Even a model 1273, stuck on a 66 MHz bus, is usable now, thanks to a K6-III+ 450, running at 400 MHz and 1.8v.