Introduction

If you expect top performance from your system, you have to accept that it all starts and ends with the CPU. Whiz-bang graphics cards and oceans of RAM won’t fix a system that’s dragged down by a pokey processor. Wether you’ew crunching numbers or rendering dimly lit hallways in Quake, the capability of your system to get the job done relies first and foremost on its CPU.

AMD K5

The AMD K5 has been coming slowly, but now it’s there and getting better and better. By now, you can get it from a PR 75 up to a PR 166. It’s FPU is still slower than the FPU of the Pentium, but it’s better than the FPU of the 6×86. It also will soon be released as a split voltage version, which will reduce heat problems of this CPU as well.

Here a table to show the weird CPU speed/bus speed/multiplier relations of the K5 CPUs:

As you can see, the PR120 runs at the same speed as the PR90, the PR100 runs at the same speed as the PR133. These CPUs obviously have got a different die. The PR120 and PR133 are more advanced than the PR90/100. This however only touches the integer performance. The FPU performance of the PR133 is the same as of the PR100.

Due to these strange multiplier settings, the K5 has got a fixed multiplier, which cannot be changed from out side via multiplier jumpers. The PR75 to PR133 will run at 1.5 multiplier regardless what the jumpers say, the PR166 will also always run at x1.75.

The Cyrix 6×86

The Cyrix 6×86 or M1, as it was called before, is a strong contender to the Intel Pentium and is able to outclass the Pentium in quite a few respects. This CPU might also be able to push technology forward more than the current Pentium CPUs, because since the 6×86 P200+ was released, a new bus speed of 75 MHz turned up at the horizon to replace the old maximum of 66 MHz of Intel CPUs. This will require new memory technology as well as new chipsets and therefore new motherboards.

This however is also the downside of the new 6×86 P200+, because you can’t run this chip in a Triton FX or HX board for they don’t support a bus speed of 75 MHz. Only to remind you — the 6×86 P200+ runs at a clock speed of 150 MHz, which is a multiplying of the 75 MHz bus speed with 2. Would you run this CPU with a bus speed of only 50 MHz and a multiplier of 3, you would loose all the speed advantages due to this pathetic slow bus speed.

Technical Specifications of the 6×86

• Clocking 2x, 3x bus-to-core clock multiplier, no 1.5 or 2.5 clock multiplier!
• L1 Cache 16-KByte; write-back; 4-way associative; unified insTRuction and data; dual-port address
• Bus 64-bit external data bus; 32-bit address bus
• Pin/Socket P54C socket compatible (296-pin PGA)
• Compatibility Fully compatible with x86 operating systems and software including Windows 95, Windows, Windows NT, OS/2, DOS, Solaris and UNIX
• Floating Point Unit 80-bit with 64-bit interface; parallel execution; uses x87 insTRuction set; IEEE-754 compatible
• Voltage 3.3V core with 5V I/O tolerance
• Power Management System Management Mode (SMM); hardware suspend; FPU auto-idle
• Multiprocessing Supports SLiC/MP(TM) and OpenPIC(TM) interrupt architecture
• Burst Order 1-plus-4 or linear burst

Problems with the 6×86 and the solution

Performance Enhancement Software

• 6xopt074.zip

  6×86 optimizer written by Mikael Johansson. Configures 6×86 CPU registers to increase performance. Additionally it enables Windows95 to ‘see’ the 6×86 CPU in the device manager.

• directnt.zip

  Enables 6×86 cache under Windows NT 4. For all the Microsoft impaired NT users.

The Cyrix 6x86L CPU

I’ve been accused to be biased against the 6×86 by several people and to eventually end this stupid accusation I would like to explain myself.

The 6×86 CPU was not a child that came to the world and was making every person, that had to deal with it, happy straight away. The 6×86 had it’s problems and Cyrix had to fight with a lot of trouble since the 6×86 release. However this doesn’t say that Cyrix wasn’t working extremely hard to survive by fixing one problem after the other. The latest improvement the 6×86 has received from its creator is the most pleasing one and eventually now I am happy with the 6×86 as well. The letter ‘L’ behind the CPU name is making all the difference to me and hopefully to all the possible 6×86 buyers as well.

The ‘L’ stands for ‘low voltage’ and doesn’t say anything else as that the 6×86 now also has got the ‘split voltage’ feature known from the newly released Pentium MMX. Now for the Pentium this isn’t making much of a difference, since the Pentium never had to fight any serious current or heat problems. For the 6×86 however, this could be the final liberation from his bad name as ‘chip fryer’.

The 6x86L has just as the Pentium MMX a 2.8 V core and a 3.3 V I/O interface voltage. Cyrix expects a power reduction of more than 25% of the previous models, which will keep the CPU much cooler and won’t ask for more current than a Pentium MMX.

This is probably the solution for all the people who have been scared by the recent problems with the 6×86. Unfortunately it comes a little bit late, since everyone is waiting for the M2 and the Pentium MMX 200 is much faster than a 6×86 P200+ (which is even on a lower level than the Pentium MMX 166 in most applications). However, who thinks that a P200+ is still by far fast enough and who doesn’t want to spend as much money as for Intel CPUs, should get a 6x86L and nothing else. Getting an old 6×86 without the ‘L’ now is considered to be completely crazy, unless the old single voltage 6×86 shouldn’t be considerably cheaper than the 6x86L.

The Intel Pentium Classic

Things You Should Know Before You Buy A Pentium

I don’t think there’s too much to say about the Pentium, because there’s that much information already being released on the net and in magazines. However there’s one important thing, which doesn’t seem to be known too well. It’s the fact that Pentiums of the same clock speed are not all the same, but can be VERY different, and you should know that before you get one ! There are now three reasons for that to be considered:

• Second class Pentiums, which require a higher voltage or are not capable of multi processing

  Intel is actually releasing different kinds of Pentiums. Some are not capable of multi processing, others have to have a higher supply voltage to run correctly. You have to realize, that Intel is not having a different production line for each clock speed, but is in real now producing more or less only one dye. After the chips have been produced, they are tested, and regarding how they performed in the test, the clock rates are chosen. Some chips would work correctly on a special clock rate only with a higher voltage, which means also getting hotter. Others wouldn’t work with multi processing. To find out which kind of CPU you have or are offered, you have to have a look on the bottom side of the chip, where’s written something like e.g. SK 106 SSS. These last three letters can tell you what kind of CPU you have, and here’s the list. It’s obvious, that you should try hard getting a chip, that runs at 3.3 V(Standard) rather than 3.4 to 3.6 V (VRE), and maybe it makes you feel better to know that you’ve got a real Pentium, that works with multi processing as well, though you won’t be able to use multi processing on a Triton board. If you should be into overclocking, it’s almost inevitable to get a SSS-chip, because than you still can increase the voltage on the motherboard to get it running at a higher clock speed (as long as you cool it well!).

  So again, have a look at the Pentium Processor Reference Table!!!

• Pentiums with faked clock rate markings

  I don’t know how big this problem is in the States, but in Europe there are a lot of faked Pentiums around. At the beginning, when Pentiums didn’t have a marking at the bottom side as well, the CPUs were just grinded off, a new marking was lasered in and the writing was printed on it. This changed a Pentium 75 quick into a Pentium 90 or 100, and you only could find it out by actually measuring the thickness of the ceramic body in at least tenths of a millimeter (2.8 mm is the correct thickness), which would reveal the faked CPUs being slightly thinner. Now they additionally put absolutely real looking black stickers on the bottom of the chip as well. It’s very hard to avoid being betrayed that way, but if you should buy one, at least try if you can remove a black label on the bottom of the chip, which reveals the real ceramic bottom side and the real marking. Only buy in shops that you can trust!!!

Additional Links

• The Intel Pentium Classic
• Product Information
• Pentium® processor FAQs

The Intel Pentium MMX

The Technical Advantages of the Pentium MMX over the Pentium Classic

• doubling of the L1 caches, 16kB data and 16 kB instruction cache
• data cache now 4 way set associative — only 2 way set associative in Pentium classic
• doubling of the Write Buffers, now 4 instead of 2
• new branch prediction unit, taken from the Pentium Pro
• implementation of a Return Stack, as known from the Cyrix/IBM 6×86
• increase of the U and V Pipelines by one step
• improvement of the Parallel Processing Ability of the two pipelines
• the MMX instruction set with the ability to pair up two MMX instructions in one go, hence 2 SIMD instructions can be processed with 16 byte data in one clock cycle
• new split voltage technology, 2.8 V for CPU core, 3.3 V for CPU I/O interface

Additional Links

• The Technical Manuals
• The Application Notes
• If you REALLY want to know what MMX is about, here you can have a look at the new MMX CPU instructions.
• For Assembler/Machine Code Freaks I found a link with all Mnemonics/Opcodes of all x86 CPUs. Maintained by Jesper Pedersen.
• Intel’s MMX Speeds Multimedia
• Intel’s Geography Lesson