66mhz would be a fast clock used somewhere .. divided down to get processor clock - and bear in mind that marketing causes companies to say things that aren't always truly obvious.

I don't recall exactly what 386 flavors did, but often it can be things like:

- We'll call it 33mhz because we think our slower but improved design behaves just as fast as a real 33mhz CPU.

- Some little circuit in our CPU runs an 33mhz, so we'll call it 33mhz.

- Access to the outside world is slower, but the CPU does run a 33mhz in cache when there are no other buss conflicts.

So -- you can't always trust speed ratings to reflect real world conditions. As long as something is working and is "fast enough" - it's good.

Sorry Dave, but this doesn't answer to my questions from previous post. Could you please confirm or deny them?

Sorry, not knowing your board, I can't give definitive answers - I can only give you information from what experience I have with PC boards which *might* help you figure it out.

-- I have a LOT of experience with embedded systems and various other non-PC type computers. But what I know of PC's has come from having had and used some of them since the original 5150 PC came into being (some 40 or so years) - I never designed a PC and only have debugged them as much as needed to keep my own various systems running well.

In this case, I though I had read a question from you relating to on clock rate/speed, and was trying to let you know some of my experiences with manufacturer specifications that that sometimes you need to take them with a "grain of salt".

WHAT ARE YOU TALKING ABOUT. UNBELIEVABLE. You have LOT of pc experiences, but you can't answer one general question. Thanks for trying anyway.

Guys, thanks to "all" for your help. I think we can close this case. There will be one more new topic from me about another board which isn't working - QDI
V4P895GRN/SMT.

Gavrilo wrote on 2025-11-09, 15:55:

Yes, but if there is no jumper on turbo switch header or no switch set to OFF, the processor should run at 8MHz only, right? With jumper or switch set to position ON the turbo should activate 33MHz, even if there is 25MHz processor? What is not clear to me yet is the function of the oscillator, why it is 66MHz. The oscillator gives the processor 33MHz while turbo is ON?

I have 486DX2 66 MHz with turbo switch connected to the header to position 2,3 according manual but it does not make any difference. It is because the cpu frequency is fixed with appropriate jumper?

Yes, a 66Mhz crystal always means 33Mhz CPU speed regardless of which CPU is installed (CLK / 2). This is fixed on all 386 boards and CPUs.

Turbo Off usually reduces speed to 8Mhz. It can also be changed by holding Ctrl-Alt and using +/- keys.

Gavrilo wrote on 2025-11-10, 15:52:

WHAT ARE YOU TALKING ABOUT. UNBELIEVABLE. You have LOT of pc experiences, but you can't answer one general question. Thanks for trying anyway.

I guess it depends on how you define "experience" , and relating to exactly what.

I have written some fairly complex and well known applications running under DOS on PCs. Inc including many tools that access PC peripheral hardware directly.

But... you are asking specific questions about "deep inside" a PC-core - clock rates, what certain jumpers can/cannot do on certain mainboards, and
questions relating to system/CPU clock generation and control signals.

I've never designed a PC, and haven't used anywhere near all the boards that are/were available. I've never had to dig very far into my own
systems other than change a CPU, swap/diagnose memory problems etc. - so I DON'T claim to be any sort of "unknown drip under pressure"**
when it comes to solving PC core hardware problems. - I'm sure there are MANY more qualified people than I to address these kinds of questions.

** "X" marks the unknown, "spurt" is a drip under pressure - work it out 😀

Sorry to disappoint so much - I'll refrain from commenting further.

DaveDDS wrote on 2025-11-10, 20:23:

Gavrilo wrote on 2025-11-10, 15:52:

WHAT ARE YOU TALKING ABOUT. UNBELIEVABLE. You have LOT of pc experiences, but you can't answer one general question. Thanks for trying anyway.

.....Sorry to disappoint so much - I'll refrain from commenting further.

You're not the only one!
Never saw a guy who asks for help here on Vogons, and then mocks others who tried to help him?!? Even though he got all the answers he asked....
To bad You can't block users here....i would, for sure! Only good things is that he has nick to remember 😉

Bus clock seens rigt for 33mhz/4 = 8.25mhz.. but dma clock is 7,16mhz ?

butjer1010 wrote on 2025-11-11, 08:19:

You're not the only one! Never saw a guy who asks for help here on Vogons, and then mocks others who tried to help him?!? Even t […]
Show full quote

DaveDDS wrote on 2025-11-10, 20:23:

Gavrilo wrote on 2025-11-10, 15:52:

WHAT ARE YOU TALKING ABOUT. UNBELIEVABLE. You have LOT of pc experiences, but you can't answer one general question. Thanks for trying anyway.

.....Sorry to disappoint so much - I'll refrain from commenting further.

You're not the only one!
Never saw a guy who asks for help here on Vogons, and then mocks others who tried to help him?!? Even though he got all the answers he asked....
To bad You can't block users here....i would, for sure! Only good things is that he has nick to remember 😉

He didn't mock, he expressed frustration about the word salad. The question was only "hey, does 66Mhz crystal = 33Mhz CPU, yes/no?".

MikeSG wrote on 2025-11-11, 12:40:

butjer1010 wrote on 2025-11-11, 08:19:

You're not the only one! Never saw a guy who asks for help here on Vogons, and then mocks others who tried to help him?!? Even t […]
Show full quote

DaveDDS wrote on 2025-11-10, 20:23:

.....Sorry to disappoint so much - I'll refrain from commenting further.

You're not the only one!
Never saw a guy who asks for help here on Vogons, and then mocks others who tried to help him?!? Even though he got all the answers he asked....
To bad You can't block users here....i would, for sure! Only good things is that he has nick to remember 😉

He didn't mock, he expressed frustration about the word salad. The question was only "hey, does 66Mhz crystal = 33Mhz CPU, yes/no?".

Yes MikeSG, that was exactly it. Frustrated about some answers. Thanks for support. And guys, sorry for that, I let myself hijacked a bit. Apologize.

weedeewee wrote on 2025-11-08, 21:51:

When using one of the benchmark programs to figure out the clockspeed the cpu is running at, be sure to add a jumper to the turbo pins on the motherboard to see what effect toggling the turbo mode on/off gives. Sometimes it switches between oscillators, on other mainboards it switches cache off, ...

enjoy.

Thanks, this is another possible answer to my question about the turbo function related to the oscillator or not.

By the way, the board was dying and resurrecting again. It must be malfunctioned somewhere deeper. Tried those 9chip memory modules and I also removed all cache chips. Nada. So the board is right now in state without beeping.