This blog entry is a translated version of my original Hungarian version.

The Preparation

My friend was able to run Windows 7 on a Pentium MMX class CPU powered machine. After few days of research and discussion I had several ideas to squeeze the resources.

First try

I used the reproduction of previous test as a basis. For Win7 install a K6 III+ and 512MB SDRAM were used. A PCI based S3 drove the display. The install was rather quick, just 4 hours. After the install a Cyrix 6x86MX replaced the K6 and only one 128MB memory module remained.

Ideas

In the mean while we reduced the possible scenarios:

- Replace of crystal
- Reprogram clock gen
- Find a slower mainboard.

Soldering

The reference clock was running on 14.31818MHz, but fortunately I had more than a dozen crystals in talon.

I warmed up the Weller and attacked the mainboard. I soldered a 1MHz crystal into the main board.

I was not so happy, because it was a fail. It was too slow, so the oscillator or the bus was not able to handle such reduction. After several replaced crystal I found 10MHz suitable. It meant 46MHz FSB instead of 66MHz. Not bad, but I was (and I am still) not satisfied.

Assembly

I was also frustrated when I had checked the clock chip. The datasheet told that it was a not progammable version. Well the idea was elegant, to share here:

Write a small program which programs the IC before the Win7 loader is started. It can be loaded into the memory and jump to the MS loader when it is done.

Check the yard

The last idea was to find a 6x86MX and Pentium 75 capable board. Pentium 75 meant 50MHz FSB, so it could be reduced more, than my board. The slowest FSB of my VIA is 66MHz. My friend has tons of old boards. After a short rummage he lent me an Aristo board, 16MB SDRAM and a brutal Trident 9000D

I was not lucky again. The BIOS of Aristo 5VIA5S is not compatible with Windows 7. It has some ACPI problem. However the 16MB module and the 256kb Trident gave me something to think of.

The final rig

Here is the final machine:

Motherboard: VIA MVP3 Super Socket 7
CPU: Cyrix 6x86MX 93MHz
Memory: 80MB SDRAM (64+16)
VGA: Trident 9000B 256kB
OS: Win7 Starter

Testing

Below you can see a quick measurement how the startup depends on memory size. The clock started at Windows loader screen and finished whe the sart menu rolled over. It does mean I was able to navigate in Start menu after few minutes, but it never finished swapping.

The second run was a quick GPU-Z. It was not able to identify TVGA9000. The resolution was an amazing 640x480 with 16 colours.

You can see below the CPU utilization when the system is loading control panel. The HDD swapped like crazy even if there was no load. At that stage the system had 96MB of memory.

You may not believe, but I was able to start IE and download Everest. The install finished after 5min 46 sec. After the installer had finished I started the test and went for dinner. The results were not bad as the Cyrix CPU is "strong" in integer.

At the end of this entry I would like to say big thanks to Bacsis as he lent me at least half of the rig.