I don't know the answer for the first two questions, but for the last one, it's probably like on my 386SX : if you put a 80387DX-33 alongside a 40MHz CPU, it'll probably get overclocked to 40MHz, like my Cyrix fastmath 20 gets overclocked when used in my 386SX 25MHz

But that shouldn't be a big deal, 7MHz shouldn't hurt too bad.

And also, iirc Intel made a mechanism to desynchronize the FPU from the CPU, you should check that as well ^^

aries-mu wrote:

Hi guys, I was wondering:

• Will Am386 DX(DXL)-40 work on any 386 motherboard? I'm quite familiar on 486 motherboards, but I know nothing about 386 mobos bus limitations.

On one of my boards i just changed the clockcrystal so my dx40 was running at 40mhz.

Deksor wrote:

I don't know the answer for the first two questions, but for the last one, it's probably like on my 386SX : if you put a 80387DX-33 alongside a 40MHz CPU, it'll probably get overclocked to 40MHz, like my Cyrix fastmath 20 gets overclocked when used in my 386SX 25MHz
But that shouldn't be a big deal, 7MHz shouldn't hurt too bad.
And also, iirc Intel made a mechanism to desynchronize the FPU from the CPU, you should check that as well ^^

Interesting! Thanks! And, maybe, just to be on a safe side, I could somehow stick a heatsink on it, just in case...

McBierle wrote:

On one of my boards i just changed the clockcrystal so my dx40 was running at 40mhz.

Oh, is there a typo when you say "my dx 40"? I didn't understand what you mean...

OMGosh! what's this crystal thing? Where is it? How do I change it? Where do I buy a 40mhz crystal???? THANKS!!!

The DXL versions featured advanced power management functions and used less power. Apart from that, they are identical to their standard DX counterparts.

Many 386 motherboards allowed you to run your math co-processor asynchronously (i.e., at a different clock speed) than your CPU. Check the jumper settings for your motherboard. This should also tell you which frequencies (clock speeds) it supports.

jesolo wrote:

The DXL versions featured advanced power management functions and used less power. Apart from that, they are identical to their standard DX counterparts.

Many 386 motherboards allowed you to run your math co-processor asynchronously (i.e., at a different clock speed) than your CPU. Check the jumper settings for your motherboard. This should also tell you which frequencies (clock speeds) it supports.

Ok, thanks!

aries-mu wrote:

Hi guys, I was wondering:

• Will Am386 DX(DXL)-40 work on any 386 motherboard? I'm quite familiar on 486 motherboards, but I know nothing about 386 mobos bus limitations.

Took the opportunity and tested this JATON 386-DX-40 CPU module I got some months ago...

...in a really ancient 386 board:

Powers on without problems.

Predator99 wrote:

Took the opportunity and tested this JATON 386-DX-40 CPU module I got some months ago... […]
Show full quote

aries-mu wrote:

Hi guys, I was wondering:

• Will Am386 DX(DXL)-40 work on any 386 motherboard? I'm quite familiar on 486 motherboards, but I know nothing about 386 mobos bus limitations.

Took the opportunity and tested this JATON 386-DX-40 CPU module I got some months ago...

IMG_9699f.jpg

IMG_9702b.jpg

...in a really ancient 386 board:

IMG_9698r.jpg

Powers on without problems.

Woow man! That's great both for the thing itself and for the data provided!

THANKS!

Enjoy your beefed-up very ancient 386 board! 😁

Before disassembling again...

...Am386 DX/DXL-40 also no problem 😀

Predator99 wrote:

Before disassembling again... […]
Show full quote

Before disassembling again...

IMG_9704r.jpg

IMG_9705r.jpg

...Am386 DX/DXL-40 also no problem 😀

Wow! It seems to me that those older systems were more sturdy, flexible, and less pain with jumpers and stuff.

It'd be interesting to assess if it is running at 40 MHz or being downclocked!

Too lazy to install a HD controller at the moment for diagnostics...but there is a 32MHz crystal, therefore it should run at 16MHz with all CPUs.

Predator99 wrote:

Too lazy to install a HD controller at the moment for diagnostics...but there is a 32MHz crystal, therefore it should run at 16MHz with all CPUs.

🤣 I understand you bro! 🤣

What's this crystal thing? The other guy above said he "replaced" it to have the system run at 40 MHz if I recall correctly. How can it be replaced? Where to buy a 40 MHz crystal? Why 16 MHz if your crystal is 32MHz? Do you mean the BUS?
What about the BUS with the 386 CPU at 40 MHz? Does the ISA bus run at 20 MHz if the 386 runs at 40 MHz? Does it require a 40 MHz crystal or 20 MHz crystal?

thanks man (sorry for the bunch of questions)

If you want more information about clock frequency changes, check out this thread. Some motherboards are adjustable by jumper, and others require a changed crystal oscillator.

You can see the oscillator in the picture of my motherboard. The rectangular silver object immediately to the right of the third ISA slot.

fitzpatr wrote:

If you want more information about clock frequency changes, check out this thread. Some motherboards are adjustable by jumper, and others require a changed crystal oscillator.

You can see the oscillator in the picture of my motherboard. The rectangular silver object immediately to the right of the third ISA slot.

Oh so that's the famous crystal! Thank you so much!!!

OK, great info.