How to light up the Pentium-50?

[OrBit]

Hey Gentlemen:

Before that, I was not sure whether the Q0335 was a pentium-50. I couldn't light it on the Pentium 60/66 motherboard, and I knew that the motherboard that can support 50MHz was also very difficult to find.

Recently, I suddenly got a great idea. Maybe I can adjust the motherboard to the operating frequency of 50MHz by changing the crystal, so that I can verify whether it is a real pentium-50

So I bought a bunch of crystals to complete this test. The results are satisfactory, so I would like to share the test process with you.

Some of the crystals:


Q0335 with the 50Mhz crystal.


Screenshot of the testing


Q0335 with the 33Mhz crystal.


Screenshot of the testing


So, can Q0335 support lower frequency? Unfortunately, it doesn't light up at 25MHz.

Result:
Pentium-50(Q0335) 25Mhz Fail, 33Mhz OK,50Mhz OK, 60Mhz Fail, 66Mhz Fail
Pentium-66(SX950) 25Mhz Fail, 33Mhz OK,50Mhz OK,60Mhz OK, 66Mhz OK

Any comment will be appreciated

Henry

[OrBit]

Since the crystal can be replaced to reduce the frequency, I would like to know what is the lowest running frequency of my 386 motherboard? 16Mhz？ 12Mhz？ Or lower?

Yes! I got the 0.946Mhz record.



I believe it should be the 386 CPU running at the lowest frequency in the world. but I still have reason to believe that 0.5MHz should be the lowest frequency it can work.

Henry

[xsecret]

What was the original frequency of the crystal on the 386 board ?

PS : Very nice Pentium 50! (The very first P5 ES was clocked at 40 MHz )

[gekaufman]

I believe the AMD 80386 can be varied all the way from 0 to their rated speed, so if you really want to go slow, go AMD!

[xsecret]

[Alitoutou]

Well done. I've been looking for socket4 mainboard that supports 50Mhz for years.Nothing gain.

[xi11west]

Very nice!

[frag_]

Cool!
It has relatively narrow working frequency window.

[Neology]

Awesome finding.

Btw, What socket 4 motherboard do you use to test the P50?

[bccwchan]

Unbelievable testing.

Good job!!!

[xiaoyanxu]

I want to know how it feels to run windows95 on Pentium-50 (Q0335).

[bccwchan]

[OrBit]

[OrBit]

Do you want to know the lowest running frequency of 80486 CPU? Today I will continue to test.

The final result :
A80486DX33 8Mhz OK
A80486SX20 0.996Mhz OK (world record of lowest I believe)

Replace to 1Mhz crystal:



It took more than 30 minutes for the system to start and complete DOS startup, which was the longest waiting.



The ISA 3486 II motherboard set show (32M Ram+TVGA8900D+XTIDE):

[xsecret]

With a frequency generator plugged on the crystal socket, you can go down to 1 Hz. I used that trick a few times for the UCA dev.