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Socket 939: New Socket, New Athlon 64s
Socket 754 Chipset Shootout
Athlon 64 FX-53 and 3.4 GHz P4 EE: Premium CPU Shootout
Prescott: The New Pentium 4 Reviewed
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K6-III+: Super-7 to the Limit
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question on low-power CPUs
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Recipe For Revival: K6-2+
By Jasin Robertson
Monday, July 24, 2000 8:03 AM EDT

Hold on to your Socket-7/SS7 motherboards and get ready for the final installment of AMD's long line of Socket-7 Processors. AMD's K6-2+ promises to breath new life into that aging Socket-7/SS7 system that so many of us have held on to for years in hope of pushing the envelope just a little further. Just when it seems like the end of the road for Socket-7 something comes along that never ceases to amaze me. First it was AMD pushing socket-7 past the Pentium-233MMX with the K6-266 & 300MHz CPUs when Intel abandoned the Socket-7 platform. Then AMD added SIMD instructions and the K6-2 was born. With integer power to spare, the K6-2 became an immediate success. Added 3Dnow! support gave hardcore gamers budget rigs. Next came the K6-III, which was essentially a CXT core K6-2 with 256K of full speed on die cache and up to 2 Megabytes of Level-3 cache depending on the motherboard used. Clock for clock the K6-III could trounce just about anything available at the time, unfortunately the K6-III maxed out at 450MHz (few 500MHz units were shipped). Another drawback of the K6-III was its un-overclockability due to the L2 cache and power requirements of the processor, the K6-III could rarely overclock more than 50-75MHz.

Enter the K6-2+. By shrinking the die to an .18 micron process, AMD was able to lower the voltage requirements of the K6-2 core to 1.4-2.0v depending on the Power Now stepping. Obviously we are going to focus on the K6-2+ for the desktop without utilization of Power Now. The K6-2+ has 64K of full speed L1 Cache, 128K of on die full speed L2 cache, and once again, up to 2 Megs of L3 depending on the motherboard. The K6-2+ also comes with 24 extra 3Dnow! Instructions which first appeared in the Athlon. The K6-2+ speed grades include 450MHz, 475MHz, 500MHz, and 550MHz. Some of you may have already seen the K6-2+ in laptop computers worldwide. 450-475MHz versions disappeared to OEMs, while the 500MHz version is publicly available in units of 1 for $79.00 each. The K6-2+/550 will be available as soon as the OEMs slow down the ordering and a reseller can order quantity in Q4-2000, which is only a few months away. I also acquired information that a 600MHz version will be launching soon to OEMs and should be available to consumers in Q1-2001. The bad news however is that this will be AMD's final Socket-7 Processor unless there is an extremely high demand for the K6-III+. Socket-7 1995-2001 R.I.P. This time frame makes Socket-7 the longest lasting socket configuration with speed grades from 75MHz-600MHz!

Duron or K6-2+?

One re-occurring argument about the K6-X series is whether to buy a Duron or upgrade to a K6-2+. The answer is easier than you think. First, let's look at a fair cost comparison on a new CPU, Case, and Motherboard. For comparison purposes I will leave out shipping charges and use lowest cost (Pricewatch) equipment.

K6-2+ System

  • K6-2+/500MHz-$79.00
  • PC-Chips/T-100-$49.00
  • AT-Case-$12.00
Total Equipment Cost=$122.00

Duron System

  • Duron/600MHz-$76.00
  • Gigabyte GA-7ZM-$123.00
  • ATX-Case-$22.00
Total Equipment Cost=$221.00

As you can see the Duron is clearly a better value considering the relatively minimal cost difference ($99.00). The performance of the Duron is definitely worth the extra cost. Now let's look at an existing K6-X based system based on an AT form factor motherboard and Case

K6-2+ Upgrade

  • K6-2+/500-$79
Total Equipment Cost=$79.00

Duron Upgrade

  • Duron/600MHz-$76.00
  • Gigabyte GA-7ZM-$123.00
  • ATX-Case-$22.00
Total Equipment Cost=$221.00

This time the difference is a bit more significant. At a price difference of $142.00, the upgrade cost of a Duron system is almost three times more than the K6-2+. In this case, the K6-2+ becomes much more appealing. Another added benefit of a "Chip for Chip" upgrade is the fact that you won't have to reformat the entire system, which is commonly the case when changing motherboards.

Compatibility

The requirements for the K6-2+ are quite simple and most SS7 motherboards should at the very least come close enough to being compatible. The most important issue is the voltage. At 2.0v, the .18-micron K6-2+ runs very cool, enough even to run at default speed and voltage without a fan attached to the heatsink. A Vcore of 2.2v is acceptable with a heatsink/fan combo. The second requirement would be the ability of the system BIOS to recognize the CPU properly. Upon posting, the screen should read K6-2+ at XXXMHz. If the bios does not recognize the K6-2+ properly then it will most likely read K6-2 - ??? At XXXMHz. This is similar to the recognition string of the K6-2 in older motherboards that recognized them as a K5?? Or 486DX/66 or AMD-Unknown. The only problems that occurred back then was the inability of the bios to enable the L1 cache. Therefore third party programs were created to alleviate this problem by enabling the L1 cache on the fly from within windows, along with other features such as write allocation, ewbe, hlt commands and linear frame buffer optimization. There is no reason that this same solution cannot be used with the K6-2+ series. The P5-A that I used for testing detected the K6-2+ as a "-XXXMHz MMX" and did not allow write allocation in the bios.

Issues and Solutions for Older Socket-7 Systems

Older VX,TX,TX-PRO,SIS,Ali and older based motherboards usually do not meet the voltage requirements of the K6-2+. 2.5v may have worked with the K6-2 and K6-III but those voltages would surely make a quick key chain out of a K6-2+, so don't even think about it. A simple solution for the voltage issue would be a voltage adapter from either Powerleap or Concept Manufacturing. Both companies make voltage adapters that will allow even the oldest single plane voltage based motherboards to utilize split voltage down to 2.1v. Another consideration is bus speed. If your stuck with a 66MHz bus then 6.0X66=400MHz is your limit and I would recommend a K6-III/350MHz instead, which are currently priced at around $50.00. with a little extra cooling you should easily be able to overclock to 400MHz with no problem. 75MHz and 83Mhz bus speeds are very common on late model socket-7 boards and will yield speeds of 450MHz-500MHz

Performance

Before we begin benchmarking, understand that the K6-2+ is not considered a "Power User" CPU. The purpose of the K6-2+ was designed for Mobile-Laptop Computers and not "Gaming Rigs".

Benchmarks

I wanted to keep this short, so all tests were done at 1024X768 under the following configuration using Quake-III's Demo-1, Unreal tournament's Flyby intro, 3dmark2000 at default settings of 1024X768/16bpp and Sis Sandra "Millennium" released 7-14-2000. All tests were done with a Voodoo3/3000 at 200MHz. I'm sure we will soon see how well the K6-2+ performs with higher end video cards such as the GTS, Radeon, Voodoo5500 and the GeforceMX

System Configuration

  • ASUS-P5-A/B
  • 256 MB CAS-2 PC-100 RAM
  • Voodoo3/3000 @ 200MHz
  • SB-Live
  • Toshiba 6XDVD
  • HP 2X2X6 CD-R/RW
  • Creative Labs Espirit DVD Decoder
  • Zip-100 Internal
  • 6.4 GIG UDMA
  • Creative Labs ISA V.90
  • Creative Labs External V.90

To save time, all game tests were done with all features enabled and set to the highest texture and detail allowed by the game at 1024X768.

Quake-III/Demo-1

ProcessorResult
K6-2/500 25.4
K6-2/550 27.7
K6-2/600 30.3
K6-III/500 48.6
K6-2+/500 43.1
K6-2+/550 44.8
K6-2+/600 47.1

Unreal Tournament (Flyby Demo)

ProcessorResult
K6-2/500 34.1
K6-2/550 36.3
K6-2/600 39.0
K6-III/500 38.3
K6-2+/500 35.2
K6-2+/550 37.2
K6-2+/600 39.3

3Dmark2000

ProcessorResult
K6-2/500 1278
K6-2/550 1403
K6-2/600 1552
K6-III/500 2074
K6-2+/500 1648
K6-2+/550 1893
K6-2+/600 2092

SISoft Sandra Millennium (Memory)

ProcessorResult
K6-2/500 113/114
K6-2/550 134/136
K6-2/600 145/148
K6-III/500 205/220
K6-2+/500 161/190
K6-2+/550 187/212
K6-2+/600 205/239

Now we can see how the top three socket-7 processors stack up. The K6-2 fails to perform remotely close to either of the higher-end CPUs, even when clocked 100MHz higher. Being left behind in Quake-III and 3Dmark2000 by 30%-60% at the same clock speed as the K6-III/K6-2+ shows that the K6-2 is definitely not a viable option for an upgrade. The K6-III still outperforms the K6-2+ in every benchmark at the same clock speed. The K6-2+, however, performs and scales very well thanks to the full speed on die cache.

The Sandra memory benchmark improved by about 25% with Write Allocation enabled, so it is definitely worthwhile making sure this feature is enabled on your system.

Conclusion

Well, I guess that just about sums it up. Is the K6-2+ everything that Socket-7 users hoped for? At $79.00, the K6-2+ can't be beat. This CPU has just about everything a budget user could ask for, low cost, Overclockability, high performance and compatibility. If you are in the market for a new budget gaming rig and want to start from scratch, get a Duron or a Celeron-2. If you own a Socket-7/SS7 and have anything short of a K6-III then the K6-2+ is your best budget upgrade option.

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