Cyrix MediaGX - The World's Fastest 486 In A Socket 7 Package
I wanted to build a Cyrix 5x86 system as that was one CPU I never owned. I was watching the CPU Galaxy channel on YouTube and he covered a Cyrix MediaGX build that he had done. I remember this processor and had actually worked on few systems with one many years ago. A little background is in order. The Cyrix 5x86 was a stripped-down version of their 6x86 CPU. They took about 50% of a 6x86 and got about 80% of the performance putting it into a 486 package. It was one of the fastest 486 upgrades out there. When Cyrix was purchased by National Semiconductor in 1997, they decided to focus on low power, embedded systems. The result was the MediaGX. It is a System On A Chip (SOC) containing a Cyrix 5x86 CPU core, memory controller, video controller, and a Sound Blaster 16 compatible audio controller. They were mostly used in notebooks and embedded control systems. There were not many motherboards for end users to put them in their systems. The CPU Galaxy video linked to seller on eBay selling MediaGX motherboards for $70. I quickly decided this was the route I wanted to go and ordered the ECS P5GX-M motherboard plus a MediaGX 266MHz CPU, memory, case, and power supply.
The MediaGX is a Socket 7 CPU, but it is not compatible with Socket 7 motherboards, as the pinouts are completely different. The motherboard has to be specifically designed for use with the MediaGX CPU and does not have any L2 cache. The only cache is the 16K L1 cache on the CPU itself. This would lead one to think these systems are slow, but as you will see, I was incredibly surprised how well mine ended up performing. Being in a Socket 7 package gives the MediaGX performance advantages over being in a 486 motherboard. The Cyrix 5x86 has a 32-bit data path and 33MHz or 40MHz FSB speed using either FPM or EDO memory. The MediaGX has a 64-bit data path, the memory clock is a divisor of the CPU clock by 3 or 4. In a system with a 266MHz CPU that would be 266/4 or 66MHz plus it uses much faster SDRAM. This makes for much higher memory bandwidth offsetting the lack of an L2 cache. When all is said and done you can expect the performance somewhere in the range of a Pentium 166-233 CPU. Here are my system specs:
Cyrix MediaGX 266MHz CPU @ 2.9v (overclocked to 300MHz)
256MB (2x128MB) PC133 SDRAM
ViewTop ET6000 4MB PCI video card (onboard video was disabled)
Integrated Sound Blaster 16 audio
3Com Etherlink III ISA network card
8GB CompactFlash card with IDE to CompactFlash adapter
16x DVD drive
1.44MB 3.5” floppy drive
Apevia Astro 450W ATX power supply
Antec VSK3000E U3 mATX mini tower case
Windows 98 SE with unofficial SP3
I ended up disabling the onboard video as this allowed me to overclock the CPU to 300MHz. This also raised the memory speed from 66MHz to 75MHz (CPU clock divided by 4. Divisor by 3 was not stable). Getting the computer running was easy, the hardest part is finding the right utility to tweak the MediaGX to it’s fullest potential. Most 5x86 utilities will fail as they identify the MediaGX as an unknown 5x86 CPU. Fortunately, there is a utility called CTCHIPZ that works on the MediaGX. Here are a few benchmarks before and after applying the tweaks.
3DBench 1.0c - 156.6 FPS
Chris's 3D Benchmark - 320x200 - 124.3 FPS
Chris's 3D Benchmark - 640x480 - 35.7 FPS
PC Player - 320x200 - 48.7 FPS
PC Player - 640x480 - 19.1 FPS
Doom - Max Details - 86.54 FPS
Quake - 320x200 - 35.2 FPS
Quake - 640x480 - 13.7 FPS
Norton SI 8.0 = 793.9
Topbench 40a - 686
SpeedSys 4.78 CPU Performance Index - 151.09
Chris's 3D Benchmark - 320x200 - 128.9 FPS
Chris's 3D Benchmark - 640x480 - 35.7 FPS
PC Player - 320x200 - 50.2 FPS
PC Player - 640x480 - 19.7 FPS
Doom - Max Details - 89.02 FPS
Quake - 320x200 - 39.8 FPS
Quake - 640x480 - 15.6 FPS
Norton SI 8.0 - 1020.6
Topbench 40a - 690
SpeedSys 4.78 CPU Peformance Index - 179.82
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