Introduction
For quite a long while we didn’t hear too much from the Texan CPU manufacturer, that used to give Intel so much trouble in the days of the 386 and 486. The AMD K5 CPU took too long to get ready and when it was released it was too late and too slow to compete against Intel’s fast Pentium CPUs. In the last three years AMD had a tough time, but they were planning smartly when they bought the CPU manufacturer NexGen two years ago. The power of NexGen was meant to be the mother of AMD’s upcoming K6 CPU and now the day has come to show the world how well this new CPU can compete with Intel’s latest processors.
For quite a while the atmosphere at AMD was getting better every day. The expectations into the K6 are high and the computer market wouldn’t wish anything more than a real tough competitor to the more and more increasing giant Intel. Intel has lately shown that its practices of ruling the computer industry aren’t exactly enjoyable. AMD and Cyrix had already several fights with Intel, but even normal people like Robert Collins or even myself had to face the strong arm tactics of this almost completely ruthless company. Intel is taking over the computer industry bit by bit and it will take more than some hopeful promises to fight off this threat. AMD’s K6 could be a serious problem for Intel’s sovereignty on the computer market and I am here now to tell you how well the K6 is prepared to take on Intel.
The Performance of the AMD K6
Well this is what really everyone wants to know. Will the K6 be faster than Intel’s Pentium MMX or Pentium Pro? What are its strengths and what its weaknesses?
I’ve tested the K6 for complete nine days. That’s certainly longer than any other computer journalist on the planet. 9 days and 9 nights I tried everything I could do with this CPU, several OS’s, several motherboards and of course several clock speeds. I’ve got hundreds of results and I’ll try to make them as clear to you as possible.
How I’ve Tested
Common for all tests was the following configuration:
- 64 MB RAM
- Matrox Millennium 4 MB, BIOS 2.5
- Quantum Fireball 1280 for Windows 95 and DOS Tests
- Seagate Cheetah ST34501W at DPT PM2144UW plus RC4040 w/32 MB EDO RAM for Windows NT Tests
The K6 ran on different boards depending on the test configuration:
- Windows 95 (Build 950, Matrox Millennium Driver 3.41) and DOS Tests:
- Tyan S1570 Titan Turbo with 512 kB cache and 12ns Corsair SDRAM for 66 MHz bus speed
- Abit IT5H rev. 1.01 with 512 kB L2 cache and 50ns Micron EDO RAM for 75 MHz bus speed
- AOpen AP5T-2 with 512 kB L2 cache and 12ns Corsair SDRAM for 83 MHz bus speed
- FIC PA-2011 with 1 MB L2 cache and 10ns Toshiba SDRAM for 66 MHz bus speed
- AOpen AP5T-2 with 512 kB L2 cache and 12ns Corsair SDRAM for 75 and 83 MHz bus speed
The Pentium MMX ran under the following conditions:
- Windows 95 (Build 950, Matrox Millennium Driver 3.41), Windows NT (Build 1381(Service Pack 2). Matrox Millennium Driver 3.06) and DOS Tests:
- Abit IT5H rev. 1.01 with 512 kB L2 cache and 50ns Micron EDO RAMfor 66 and 75 MHz bus speed
- AOpen AP5T-2 with 512 kB L2 cache and 12ns Corsair SDRAM for 83 MHz bus speed
The Pentium Pro (256 kB L2 cache) ran on
- Windows 95 (Build 950, Matrox Millennium Driver 3.41), Windows NT (Build 1381(Service Pack 2)., Matrox Millennium Driver 3.06) and DOS Tests:
- Asus P/I-P65UP5 plus C/P6ND with 50ns Micron EDO RAM
All CPUs were tested on the motherboards that offered best performance for the particular CPU.
Winstone and Winbench ran for each operation system under 1024x768x65536x75.
The Windows 95 Performance of the K6
Let’s say it loud and clear. Under Windows 95 the K6 is the fastest CPU currently available. The K6 233 reaches a Windows 95 performance that’s higher than of a Pentium MMX, still higher than of an overclocked Pentium MMX 225, higher than of a PPro 200 and equal to an overclocked PPro 233. Overclocked to 250 MHz (3×83 MHz) and 262.5 MHz (3.5×75 MHz) it’s faster than anything else under Windows 95 and even the upcoming Pentium II will have its problems with it.
The K6 166 is almost as fast as an Intel Pentium MMX 200, the K6 200 is already faster than this Intel CPU and the K6 233 shows a distance of even 4 Winstone 97 points to the Pentium MMX 200.
| WINDOWS 95 | K6 233 | K6 200 | K6 166 | Pentium MMX 200 | Pentium Pro 200 |
| Business Winstone 97 | 54.8 | 51.9 | 48.6 | 50.2 | 52.4 |
| Highend Winstone 97 | 23.6 | 22.2 | 20.1 | 22.4 | 24.8 |
| Business Winmark 97 | 98.1 | 89.7 | 78.5 | 91.4 | 84.2 |
| WinQuake 1.09 Timedemo2 640×480 | 15.5 | 13.9 | 12.6 | 15.9 | 23.4 |
As you can see, the Highend Winstone performance of the K6 is at the same level as the Pentium and definitely lower than the Highend Winstone performance of the Pentium Pro. The difference in WinQuake is even bigger. This shows that the FPU performance of the K6 is lower than the FPU performance of the Intel CPUs.
The importance of the FPU in normal applications is still very questionable. Even Quake players should have got the message by now, that you rather save some money purchasing a CPU and buy a Diamond Monster 3D instead. This enables you to play GLQuake, which is faster than any ‘only CPU driven’ normal Quake and it is looking 100000 times better.
In terms of the normal business applications under Windows 95 the K6 is the absolute winner. The Pentium II CPU at 233 MHz will probably be just as fast or maybe slightly faster, but for a much higher price.
The Windows NT Performance of the K6
Under Windows NT, the K6 is still making a good figure, although the distance to its competitors from Intel isn’t big at all. The K6 233 is under Windows NT exactly as fast as a Pentium Pro 200, it’s much faster than a Pentium MMX 200, but it’s considerably slower than an overclocked Pentium Pro 233 and will most likely be slower than the Pentium II at the same clock speed as well.
| WINDOWS NT 4.0 | K6 233 | K6 200 | K6 166 | Pentium MMX 200 | Pentium Pro 200 |
| Business Winstone 97 | 71 | 67.6 | 63.3 | 64.3 | 71.2 |
| Highend Winstone 97 | 26.9 | 24.5 | 22 | 24.2 | 29.2 |
| Business Winmark 97 | 104 | 93.5 | 83.6 | 87.5 | 104 |
| Winbench 97 CPU Mark16 | 465 | 414 | 362 | 423 | 360 |
| Winbench 97 CPU Mark32 | 559 | 513 | 466 | 420 | 554 |
You can see again, that the K6 166 is giving the Pentium MMX 200 a very good run for its money. The Pentium Pro 200 can still show his muscles with his internal L2 cache and the faster FPU in the Highend Winstone. However, considering that the K6 has to run with slow 66 MHz clocked L2 cache, it’s performing quite well.
Lots of us would have loved to see the K6 performing even better under NT, because that’s the old domain of the Pentium Pro and will be the play ground of the upcoming Pentium II, which is at least as fast as a Pentium Pro at the same clock speed. Hence the K6 will not be faster than a Pentium II under Windows NT at the same clock speed, but it will be much cheaper than the Pentium II as well.
The DOS Performance of the K6
Today the DOS performance of a computer system is most likely the least important one. Hardly anybody is still using DOS for any business applications, but there are still several computer games, that mainly run under DOS. For me DOS is really nothing else than a gaming OS anymore and that’s the reason why I’m only doing game benchmarks for DOS.
In this environment the K6 doesn’t really look exactly good. Quake is not one of the K6’s favorites and in other 3D applications under DOS it doesn’t look well against the PPro at all.
| DOS | K6 233 | K6 200 | K6 166 | Pentium MMX 200 | Pentium Pro 200 |
| Quake 1.06 Timedemo2 640×480 | 14.2 | 13.4 | 12.2 | 15.7 | 21.9 |
| PC Player DOS 3D Benchmark | 26.4 | 25.1 | 23.1 | 23.1 | 31 |
| 3DBench | 250 | 250 | 200 | 166.6 | 333.3 |
| Chris Dial’s 3D Bench | 38.4 | 35.3 | 31.7 | 40.7 | 49.6 |
I can only stress again, that I personally wouldn’t give anything about the Quake issue, because there’s a Monster 3D and GLQuake, which is faster and much nicer. However the K6 is compared to the Pentium Pro definitely the worse DOS gaming CPU.
The MMX Performance of the K6
I have to admit it, that because of the lack of decent MMX benchmarks, I had to use the Intel Media Bench, which of course is written by Intel and hence produced to show off Intel CPUs best. However the K6 MMX performance doesn’t even under this benchmark look bad at all. The video and image processing performance of the K6 is better than of the Pentium MMX, which I would currently consider as the most important of all these mystical MMX topics and the video performance will most likely even be better than of a Pentium II.
| Intel Media Benchmark | K6 233 | K6 200 | K6 166 | Pentium MMX 200 | Pentium Pro 200 |
| Overall | 246.52 | 214.46 | 181.58 | 246.57 | 194 |
| Video | 308.54 | 269.14 | 228.71 | 252.07 | 160.22 |
| Image Processing | 697.16 | 605.07 | 527.55 | 684.98 | 219.7 |
| 3D | 141.07 | 122.15 | 102.77 | 159.78 | 211.55 |
| Audio | 273.22 | 238.11 | 200.79 | 326.58 | 232.32 |
It is obvious, that the MMX performance of the K6 is much better than of the Pentium Pro, which doesn’t have the MMX instructions. It’s funny that the K6 233 has the same overall performance as the Pentium MMX 200 in IMB, but a better video and image processing performance on the cost of a worse 3D and audio performance. Well, which ones would you consider as more important?
The Performance of an Overclocked K6
The K6 is a very overclocking friendly CPU. This reminds me of the time when I ran my AMD 486 DX4/100 at 120 MHz without a problem. The highest speed I could run the K6 233 at was 262.5, which is 3.5 times 75 MHz, but the fastest was 250, 3×83 MHz. I hope the 266 will run at 291 MHz (3.5×83) and this will really kick butt.
The tests were run on the AOpen AP5T, which runs best and most stable at 83 Mhz. The DPT PM2144UW ultra wide SCSI controller (where the Cheetah was connected to) was managing the 83 MHz bus speed without the slightest problem.
Windows 95 Hit List
| CPU clock speed/bus speed | Business Winstone 97 |
| K6 250/83 | 58.4 |
| K6 262.5/75 | 57.8 |
| Pentium MMX 250/83 | 56.2 |
| K6 208/83 | 55.2 |
| K6 225/75 | 55.1 |
| K6 233/66 | 54.8 |
| Pentium Pro 233/66 | 54.7 |
| Pentium MMX 208/83 | 53.1 |
| Pentium MMX 225/75 | 52.9 |
| Pentium Pro 200/66 | 52.4 |
| K6 200/66 | 51.9 |
| K6 187.5/75 | 51.9 |
| K6 166/83 | 50.9 |
| Pentium MMX 200 | 50.2 |
| K6 166/66 | 48.6 |
Windows NT Hit List
| CPU clock speed/bus speed | Business Winstone 97 |
| K6 250/83 | 76.3 |
| Pentium Pro 233/66 | 75.8 |
| K6 262.5/75 | 75.1 |
| Pentium MMX 250/83 | 72.8 |
| K6 225/75 | 72.1 |
| K6 208/83 | 71.7 |
| Pentium Pro 200/66 | 71.2 |
| K6 233/66 | 71 |
| Pentium MMX 225/75 | 68.5 |
| Pentium MMX 208/83 | 68.4 |
| K6 200/66 | 67.6 |
| K6 187.5/75 | 67.4 |
| K6 166/83 | 66.5 |
| Pentium MMX 200 | 64.3 |
| K6 166/66 | 63.3 |
You can see that the K6 233 is faster even if you slightly underclock it to 225 MHz. At 250 MHz it’s even in Windows NT faster than the Pentium Pro 233 and I guess it’s no miracle to my long term visitors, that the K6 166 runs much faster at 2×83=166 MHz.
The most interesting results are the ones of the Pentium Pro. You can see the huge difference between Windows 95 and Windows NT. While it can’t beat the K6 233 under Windows 95 it’s almost the fastest CPU under NT. This must be important for your decision!! If you are a NT user or if you are planning to become one soon, the Pentium Pro is probably still the best choice, since it’s currently also fairly cheap.
The Compatibility of the K6
The K6 is very compatible to the current Socket 7. The 166 and 200 MHz versions are running at 2.9 V split voltage, which you can find on all new motherboards. The K6 233 is supposed to get 3.2 V, but it runs fine at 2.9 V as well. Only overclocking gets kinda difficult to impossible at 2.9 V. The solution to this problem is a trick with the voltage jumpers on all boards that have jumpers for single/dual voltage and other jumpers for the core voltage itself. Here you can adjust the jumpers to dual voltage and the core jumpers have to be adjusted to 3.3 V. This is 0.1 V too much, but that’s ok in terms of heat and reliability and makes the CPU wonderfully overclockable. In fact this is actually the jumper setting the K6 system came with from AMD. Future boards will include the 3.2 V setting, like e.g. Shuttle boards or the Asus TX97, which falsely uses 3.1 V, but it’s running the K6 at 262.5 MHz fine. The next generation of K6 CPU’s will be manufactured in .25 micron technology and this will reduce the required voltage down to 2.8 or even less.
Software runs without any problems on the K6. I’ve tried several programs, and the operating systems you can see above. NT always worked fine at any speed with the K6, which is one of the best proves that the K6 runs reliable in overclocked condition.
To tweak the performance of the K6 to its maximum, a feature called ‘Write Allocate’ has to be enabled. This is meant to give you another 4% increase in performance. Most boards with new BIOSes will do this automatically, as I could check on all my test boards. In case your board shouldn’t do this, there’s a utility to switch on this mode manually.
Recommended Motherboards for the K6
I had the chance to test several motherboards with the K6 and I can say that it ran on each of them flawlessly, even in case the BIOS wouldn’t recognize the CPU. I’ve tried so far:
- Abit IT5H
- AOpen AX5T-1
- AOpen AP5T-2
- Asus P/I-P55T2P4 rev 3+
- Asus TX97
- FIC PA-2011
- Tyan S1570 (today!!)
I have to differentiate the results between good Windows 95 and good Windows NT performers. The fastest board under Windows NT was clearly the FIC PA-2011. This board comes with the VIA Apollo VP2 (VT82C590) chipset, which is already well known under the name AMD 640 now. The difference wasn’t big, but definitely noticeable.
Under Windows 95 the fastest board was the Tyan S1570 TitanTurbo, which is the last one I’ve tested. The differences are not big though and I can say that except of the Asus P/I-P55T2P4 all boards were within 1.5 Winstone points. The T2P4 however didn’t have a BIOS that recognized the K6, which means that the ‘write allocation’ wasn’t switched on and I think this was the reason for its worse performance.
Now the funny thing is that the Pentium MMX is not running fastest on the FIC board as well. I haven’t found a reason why yet, but it’s kinda remarkable. The Pentium MMX is still running best on a TX board for Windows NT and on the IT5H for Windows 95.
Summary
The first thing I’d like to say is that one thing is for sure: The Pentium MMX is now a completely obsolete CPU ! The K6 233 will be priced lower than the Pentium MMX 200 and it’s faster than this CPU in almost every respect. Compared to the Pentium Pro and to the upcoming Pentium II you will have to make up your mind. If you should be a Windows 95 user the answer should be clear. The K6 is faster than any current CPU under Windows 95 and will probably be just as fast as the Pentium II at the same clock speed . Under Windows NT the K6 233 is still at least as fast as the Pentium Pro 200, but it will most likely be considerably slower than the Pentium II at the same clock speed. Hence the NT user will have to know what he really wants. If he just wants the best performance, regardless for what price, he should wait for the Pentium II. If price is of importance, consider what you are doing with your system. The K6’s weakness is the FPU. If a lot of rendering power is needed, the Pentium Pro and the Pentium II are the much better choice. The K6 is also unable to run in multi CPU systems, so this will stay a domain for Intel as well for now. If you are only doing business applications however, the K6 is a very attractive alternative. There will very soon be a K6 266 and it will be much cheaper than a Pentium II. For the money you save you can get other hardware, which could make your system even faster than the Pentium II system for this price.
If you should be worried about compatibility issues, you can relax. Unlike the problems with the Cyrix/IBM 6×86, the AMD K6 is running even on boards that don’t recognize it. As long as your board is supporting dual voltage, the K6 runs on it. BIOS upgrades either now or very soon available to enable the special features of the K6 to give it maximum performance. Although the K6 233 is officially asking for 3.2 V, which is not available on the most current boards, it was running flawlessly at 2.9 V on every board I’ve tested it on.
For ‘Tom’s Overclocker Community’ this CPU is an El Dorado as well. The K6 233 runs great at 250 or even 262.5 MHz and is able to beat even overclocked PPros or Pentium II 233 at these clock speeds. This is something you get for free, so why not be happy about it? I can’t wait to test the K6 266 at 291 MHz and I’m sure that the K6 at this speed can even compare to a Pentium II 300.
All in all I’m sure that this CPU will be very successful. The current mainstream market still is the Pentium market. Whoever is contemplating the purchase of an Intel Pentium or Pentium MMX CPU can forget about this now. The AMD K6 is faster and cheaper. As long as the Pentium II isn’t officially available, the K6 is even a serious alternative to the high end system market.
The current choice is only ‘K6 or Pentium Pro’. Even when the Pentium II comes out officially (I know you can buy it already, but you can’t buy boards, haha) it will be much too expensive for its little performance increase over the Pentium Pro. The Pentium Pro is a very good CPU and its internal L2 cache is making it unique. However the K6 is still even cheaper than that, it is just as fast in most respects and it has got the MMX instructions, if this should be of importance to you (it obviously is to Intel).
