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Awhile back LGR reviews, a very popular YouTube channel that covers retro computing posted a video about building a 486 machine. It was certainly a competent machine, faux woodgrain aside but one comment in the video stuck out to me. At one point it is mentioned somewhat offhand that the AMD 486 CPU’s were known to be slightly faster then their Intel counterparts. I never had heard this before and became quite curious to the matter. After some Google searching I still could not find any reference to this. Finally I created a thread over at the VOGONS forum on the matter and it was the general consensus that the AMD chips were basically clones and performance was virtually identical. It was even brought up by a few posters that the AMD chips seemed to have a few software incompatibilities for unknown reasons with OS/2 and Netware cited as examples.

With this information in hand I decided to do my own testing and thus we have this article and the CPU face off. My goal with these tests was to perform a number of benchmarks on both CPU’s to see if there is any actual performance difference and second to attempt to install OS/2 Warp using various CPU’s to check compatibility. So lets take a look at the CPU’s we will be testing.


The two main CPU’s will be testing are the Intel and AMD 486 DX2-66 chips. These are classic 486 CPU’s both running at the exact same speed. Supposedly the AMD chip is a virtual clone of the Intel model and both of these chips have 8kb of on board L1 write-through cache though both companies also produced enhanced write-back cache versions. To keep things interesting I also decided to throw in a Cyrix DX2-66 which was also a popular CPU manufacturer at the time. Supposedly the Cyrix chip is an independent design from the AMD or Intel parts but specs wise is identical with a 66mhz running speed and 8kb of L1 write-through cache.

GIGA-BYTE-TECHNOLOGY-CO-LTD-486-GA-486VF-1The motherboard I’ll be using for these tests is the Ga-486VF rev 8B socket 3 board using a SIS chipset with 20mb of FPM RAM and 256kb of L2 cache. I’m using a CL-GD5426 based VLB video card for video output and a generic ISA I/0 controller. Since a sound card would be unused for these tests I left it off the board.

Before the benchmarking tests I wanted to give the results of the compatibility tests using OS/2 warp version 4. There are many versions of OS/2 and warp ver. 4 was all I had on hand so keep in mind earlier versions may show incompatibilities that ver. 4 does not. After my testing I found that OS/2 warp ver. 4 loaded up and ran fine on both the Intel and AMD DX2-66 chip. Warp ver. 4 however did fail to load running the Cyrix DX2-66 and on loading the OS consistently threw an error and halted the loading process.


Lastly we have the benchmark results running the standard gambit of DOS benchmarks.

dx2 mashup

So according to the results of several benchmarks as seen above the AMD and Intel chips are virtually identical performance wise. The Intel chip in most cases barely pulls ahead of the AMD chip by a hair but usually this is a less then 1 FPS difference and within the margin of error. The Cyrix chip on the other hand lagged behind a little on three out of five benchmark tests lagging by 10 FPS in quake and almost 5 FPS in DOOM. The Cyrix DX2 barely pulled ahead in PCP bench and for whatever reason was given a higher score in Speedsys test.

So what’s the final verdict? From everything the benchmarks have shown me plus personal experience and online research the Intel and AMD DX2-66mhz chips are virtually identical performance wise. The Intel does seem to be the slightest bit faster but never even exceeded more then 1 FPS or point difference in any test. I don’t think this difference is even perceivable by a human user. The Cyrix chip though was the clear loser falling behind the Intel/AMD duo and having incompatibility issues with OS/2. In most usage situations I think the Cyrix 486 would perform just fine and the average user would see little difference but given the choice an Intel or AMD DX2 is certainly the way to go. Personally between the Intel and the AMD I would choose the Intel but they appear to be identical performance wise and very close in overall software compatibility. As I stated earlier the AMD chip may have compatibility issues with older versions of OS/2 and Netware, another piece of software the AMD chip is said to have issues with but not tested by myself.



One Comment

  1. Whilst the AMD chip is most certainly a clone (in the sense that it does the same job at the same speed) I believe that they had to make their own design for it, perhaps reverse engineered to a degree? They had after all ended their co-operation with Intel sometime around the release of the 386.

    I think the Cyrix CPU suffers because they had comparatively lack-lustre FPU performance, but equal or slightly better integer performance which would explain tests where it performs better.

    anyhow, interesting to see a fair comparison.

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