A black version of the Cyrix MII 333GP. They were also available in grey and gold. IBM had black versions as well, however, with a slightly difference shade of black.

I believe that the black and grey Cyrix MII 333GP are the uncommon one. Most were so called 'goldcaps' or if they were black they have an IBM 6x86MX print on them. > Read more

Almost identical to thisIBM 6x86MX PR300 except for the clock frequency/FSB ratio. One runs at 233MHz/66FSB and the other at 225MHz/75FSB.

Since the IBM 6x86MX is essentially a Cyrix MII (same core, different name) they should perform equal to the Cyrix MII. See Cyrix MII 300GP/75 for benchmark results of both the 66MHz and 75MHz FSB version. > Read more

In early 1998 these CPUs were fine if you weren't into gaming or using floating-point intensive programs. Straight up competitor with the Pentium MMX but to make things confusing Cyrix/IBM also threw their own CPUs in the ring: the PR233 was available in both 66MHz FSB and 75MHz FSB versions. Usually the PR233/66 wins the battle. > Read more

IBM's fastest 6x86MX is the PR333 at 250MHz using a 83MHz FSB. They are based on the Cyrix MII core but the IBM 6x86MX PR333 seems to be ever so slightly faster than the Cyrix MII 333GP in the benchmarks.

Cyrix did release faster versions like the 366GP, 400GP and 433GP but since they had problems ramping up the clock frequency they relied on increasing the FSB. The 433GP is "100GP" faster than the 333GP but only increases clock frequency by 50MHz. The increase in FSB to 100MHz is nice but by far not as effective if the CPU only runs at a meagre 300MHz. > Read more

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The Cyrix 6x86MX PR200 was Cyrix's answer to the Intel Pentium 200 (and MMX). Generally it ran quite well although it ran slightly hotter than the Pentium. For Office use the 6x86 was a fine choice but for gamers Cyrix left the competition when games like Quake arrived. The floating-point unit (FPU) wasn't that strong causing the PR200 to run as fast (or slow) as a Pentium 100.

In European magazines from back in the day the 6x86MX was mentioned in adverts that sold computer parts or whole systems. Usually they sold something like a Pentium MMX 166, 200 and 233 and offered a PR200+ as cheaper alternative.

Also note that the Cyrix 6x86MX PR200 came in two different versions: one with 166MHz/66FSB and one with 150MHz/75FSB. > Read more

The Cyrix MII 400GP is the second fastest Cyrix MII processor made. It runs at 285MHz using a 3x multiplier and a weird 95MHz front-side-bus. The Cyrix MII 433GP would be Cyrix’s fastest MII ever to exist at 300MHz using a regular 100MHz front-side-bus. Both the 400GP and 433GP are uncommon since they weren't the best choice back then.

Performance-wise, it falls behind on an AMD K6-2/300. Using Quake II (floating point intensive), it will score practically equal to an Intel Pentium MMX 233, but on solely integer performance, it will be somewhat faster.

I couldn't find prices of a 400GP from times when they were new. However, I did find prices for the 300+ and 333+ versions in PC Action 1999/06 (click). Prices are in Deutsche Mark and without a CPU cooler:

6x86MX 300+	99 DM
6x86MX 333+	129 DM
K6/2 300/66	119 DM
K6/2 300/100	139 DM
Pentium MMX 200	129 DM
Pentium MMX 233	139 DM
Celeron 333PPGA	139 DM
Pentium II 333	279 DM

Based on CPU pricing, the Celeron 333 would clearly be the best choice. A Gigabyte 5AX (ALi Aladdin, So7 for Cyrix and AMD) would cost 139 DM, and a Gigabyte 6LX7 for PPGA Celeron 159 DM, which is the cheapest 440LX/So370 motherboard available. Being on a budget, you could opt for the cheapest So7 ECS P5SD-A+ motherboard using a SiS chipset, but I guess you'll trade in some performance.

All in all, the Cyrix didn't fare well when the 333GP and faster versions were available. They underperformed, and on budget-tight systems, AMD was the better choice. An enthusiast who wouldn't mind overclocking would certainly take the Celeron and overclock it.

Despite the fact that in mid-1999 the Cyrix MII wasn't up to the task, I still like them in retrospect. The ones up to 300GP could be at the base of nice Office systems in early 1998 (when the price difference was bigger, in favour of Cyrix) since they ran Windows and integer-intensive programs quite well. Competition was fierce in that time.

As I'm writing this, I have an overclocked 433GP (333GP overclocked at 3x100MHz) running with a 3Dfx Voodoo Graphics and NEC PowerVR card. It runs every game at least at Pentium 233MMX level and everything else above that . > Read more

The Cyrix MII 300GP was available in several versions. Read more about them here. > Read more

A lot of CPU's in my collection look almost identical from a distance. It's hard to tell a Pentium 100, 120, 133 or 150 apart if you aren't close enough to read the sSpec information on the chip. The logo's and detailing on CPU's often stay identical in its course of production.

There are exceptions however and Cyrix really wanted to shine as the odd one out!

1 (this CPU). Cyrix MII 300GP/66 with big MII logo
2. Cyrix MII 300GP/75 with big MII small v logo
3. Cyrix MII 300GP/66 with buig MII 'dithered' logo
4. Cyrix MII 333GP in black
5. Cyrix MII 333GP in grey
6. IBM 6x86MX PR300 in black

The latter is based on the Cyrix MII but sold as IBM product. > Read more

This Cyrix MII 333GP came in three versions: one with 66, 75, and 83MHz FSB. This version uses the 83MHz FSB and thus is clocked at 250MHz. The versions with 66 and 75MHz FSB run at 266MHz.

Intel always used 50, 60, and 66MHz bus speeds for their motherboards. Due to dividers, the PCI-bus will run within specification (33MHz or slower) if the bus is run at 66MHz or lower. Running at 75 or 83MHz FSB technically falls in the category of overclocking: at 75MHz, the PCI-bus runs at 37.5MHz. Increasing the FSB will increase the overall performance of the system. Cyrix used this method to increase the performance of their chips. After all, most motherboards can run at least at 75MHz (that is, in the time period of this CPU).

In the benchmarks you can see that the different 333GP configurations have their strengths and weaknesses. In general the higher clock frequency wins over the faster bus. This means that the 83MHz version is often ever so slightly slower than the 66MHz or 75MHz version.

Notice that the print on the chip is a little bit bigger. Cyrix seems to have at least three different sizes for their prints.

On the page with the Cyrix MII 400/95 I've written something about prices in 1999 regarding the 333GP model. > Read more

This MII 333GP has a 'V' printed on the CPU. I'm not sure what the V means but it might be because VIA acquired Cyrix by then. > Read more

Just like this 300GP but with an interesting twist: the MII-logo on the CPU is very small! > Read more

Technically this is a Cyrix CPU but IBM sold them under their name as well. I like the dark looking heat spreader that just sits on top of the 'die' (the core). You can look under the heat spreader and actually see the 'die' along with some SMD chips. Somehow that reminds me a lot of the AMD K6-2 (which looks pretty much the same if you remove the heat spreader) especially because the bottom of the CPU is just identical.

This particular IBM 6x86MX PR300 runs at 233MHz using a 66MHz FSB. I have one that runs at 255MHz/75FSB as well which you can see here.

Since it's technically a Cyrix product it should perform equal to the Cyrix MII 300GP/66. > Read more

This is the slowest Cyrix MII CPU within the MII-branding. It runs at a fairly low clock frequency but uses a 75MHz bus to speed things up a bit.

The MII ranged from 233GP to 400GP (rated). The 6x86MX actually uses the same chip as the MII but has a different name; they are available in lower speeds.

Cyrix had problems increasing the clock frequencies of the M2-chip. The 333GP runs at either 250 or 266MHz depending on the FSB-speed. The fastest production models are the 400GP and 433GP at 295MHz and 300MHz. Higher frequencies weren't possible within regular voltage and cooling parameters.

Interestingly the IBM 6x86MX PR233 and Cyrix MII 233GP use the same Cyrix MII core but perform ever so slightly different. The Cyrix MII 233GP seems to be faster. I've ran the benchmarks multiple times, rebooted, swapped CPU's but the results always favoured the Cyrix MII. Perhaps the manufacturing process caused a slight difference; I've read that IBM was made via their own 0.35nm process and Cyrix via 0.3nm National Semiconductor. Click this link to compare them in the benchmarks below (red bars show the Cyrix MII, grey the IBM 6x86). > Read more

The Cyrix MII was technically exactly the same as a Cyrix 6x86MX; the only thing different was the name!

This CPU only runs at 233MHz and uses a trouble-free, 66MHz bus. You can get these CPUs with a 75MHz bus as well but they run at a slower clock frequency. Usually a faster bus is better but at 225/233MHz frequencies a faster clock is more desirable. > Read more

Similar to the Cyrix 6x86MX PR200 but then a tad faster. This one clocks at 187MHz using a 75MHz front-side-bus so it's only 21MHz faster than the PR200 mentioned earlier. Usually the increased front-side-bus will compensate for the slightly decreased clock frequency, however, the Cyrix seems to favour a higher clock frequency over a faster bus: the 6x86MX PR233/66 at 200MHz is faster than the 6x86MX PR233/75 at 187MHz. By clicking on this link you can compare the two better as it will show the benchmark results of the PR233/66 in a grey bar and the PR233/75 in a red bar. > Read more

Cyrix's M2 was, on paper, quite an improvement over the M1R that the IBM 6x86 P200+ used. This is because the M2 is made on 350nm instead of 650nm and thus uses a lower core voltage, which causes much less heat generation. Despite this, the increased L1 cache (to 64KB instead of 16KB) results in the benchmarks not being shocking because it still lacks a decent FPU. Doom doesn't seem to fly, but the faster the CPU gets, the harder it will be to get a higher score with Doom. The PCI bus and Matrox Millennium 4MB PCI I use for the Doom benchmark are nearing their limits. It isn't surprising that Doom runs slightly better on the old 6x86 P200+ (M1R) because this CPU uses a 75MHz FSB and 37.5MHz PCI bus.

On the other side: when benchmarking the CPUs in Windows, I removed the Pentium MMX 200MHz and installed the Cyrix 6x86MX PR200 and immediately noticed that Windows ran a bit smoother. I guess the CPUMark '99 score will represent the performance in Windows quite much . MDK also seems to run a lot better compared to the 6x86 P200+.

The code on the back of this CPU is GEDD8735H. This stands for:

Code	Explanation
G	IBM
E	.35u process, 5-layer design
D	Burlington, Vt fab.
D8	Die run code 'D8'
7	1997
35	Week 35
H	Lot code 'H'

> Read more