Googling the part number reveals that's a SMD Crystal Oscillator made by Toyocom.
http://www.datasheet-pdf.com/PDF/TCO-711JTC-D … -Toyocom-544053
So Pin 1 is Enable/Disable, Pin 2 is Ground, Pin 3 is Output, Pin 4 is Vcc (in 486 era this is typically +5V).
Pin 1 has logic 1 as Enable and logic 0 as Disable.

Looking around this looks like a compatible replacement: https://www.digikey.fi/en/products/detail/ecs … X-666-TR/827460
4-pin SOJ package and 5 Volt.

EDIT: Though from the picture I can see there seems to be provisions for a trough-hole crystal oscillator too.
Would need to beep with a multimeter to make sure those are connected to the SMD crystal oscillators pins.

If you switch to the THT can type you could fit a socket to allow to switch back to a 50MHz

texspex wrote on 2023-08-05, 10:52:

EDIT: Though from the picture I can see there seems to be provisions for a trough-hole crystal oscillator too.
Would need to beep with a multimeter to make sure those are connected to the SMD crystal oscillators pins.

Hi,

I've tested continuity and there is continuity between there (kindly see picture).

Does that answer your question?

The board indeed supports either type of crystal oscillator since there is continuity between those holes and pads.
You'll have to make a decision of whether you want to use a SMD one or Through-Hole one.

texspex wrote on 2023-08-05, 18:16:

The board indeed supports either type of crystal oscillator since there is continuity between those holes and pads.
You'll have to make a decision of whether you want to use a SMD one or Through-Hole one.

In all honesty, I have no ideia what is the difference (or even if there is any).

What are the pros/cons of each?

NightShadowPT wrote on 2023-08-05, 20:23:

texspex wrote on 2023-08-05, 18:16:

The board indeed supports either type of crystal oscillator since there is continuity between those holes and pads.
You'll have to make a decision of whether you want to use a SMD one or Through-Hole one.

In all honesty, I have no ideia what is the difference (or even if there is any).

What are the pros/cons of each?

They are literally the same, just a different package

Yeah, the package of it is the difference.
So which one aesthetically you want to put in.

This one seems to be a compatible Through-Hole version: https://www.digikey.fi/en/products/detail/ecs … 200B-666/274061
DIP8 and 5 Volt.

I still say the DIP package oscillator would be preferable, simply because you can fit a socket for it

Bought both, just in case (they were 2$ each...) 😀

For the installation, do I just need to respect the "notch" orientation, solder, change the CPU and call it a day?

By the way, in case someone is interested, I ran some tests on both configurations (the 486DX2 66 without cache vs 486DX2 50 with cache)

____________|__ 486DX2 66*_|__486DX2 50**
-----------------|---------------|----------
3D bench_______|____37.0____|____34.4____(DX2/66 is 7.6% faster)
Chris 3D Bench FPS_|____27.9____|____24.4____(DX2/66 is 14.3% faster)
PCP Bench______|____9.7_____|____8.6____(DX2/66 is 12.8% faster)
Doom (Low)_____|____60.6____|____61.4____(DX2/50 is 1.4% faster)
Doom (High)_____|____20.7____|____19.8____(DX2/66 is 4.5% faster)
Quake_________|____6.9____|____5.8_____(DX2/66 is 18% faster)

* - No L2 cache
** - 256Kb L2 cache

Despite having a 32% faster clock speed, the DX2/66 only scores anywhere between 4.5% to 18% faster, with DOOM (low) being the exception with the DX2/50 being quicker (if by only 1.4%).

I am curious to see what the numbers will be when I get the DX2/66 with cache working.

NightShadowPT wrote on 2023-08-07, 16:21:

I am curious to see what the numbers will be when I get the DX2/66 with cache working.

Your new front side bus is 33MHz, the L2 cache chips seem to be 25nS. If the cache chips contain some (negative) aberrations and if you cannot adjust the cache timings in BIOS there might occur some problems you did not have with 25 MHz FSB.
Replacing the 4 cache chips and TAG chip by faster ones might help in this case.

When running a DX2/66 means sacrificing L2 cache it´s quite pointless.

No, he did not modify the oscillator yet. Yes, there is a "*" as pin one.

The cache helps with DX2 50 to bring closer to cacheless 66MHz. Once he replaces the oscillator with 66.666MHz and CPU to DX2-66 on the cache board, the cache will pull the computer more farther than cacheless 66.

Cheers,

NightShadowPT wrote on 2023-08-07, 15:44:

Bought both, just in case (they were 2$ each...) 😀

For the installation, do I just need to respect the "notch" orientation, solder, change the CPU and call it a day?

The 'dot' on the current SMD one indicates pin 1. And on the boards silkscreen for the Through-Hole crystal you can see one corner is not rounded which indicates pin 1.
So the green C in your picture is pin 1. Your new crystals should have a dot too to mark pin 1 so orient them the same way.

I've never owned a PC with a CPU Card so I don't know if it needs anything else, but I've done a crystal change to a NCR 486 Mobo and it didn't require anything else to work.

texspex wrote on 2023-08-08, 11:01:

The 'dot' on the current SMD one indicates pin 1. And on the boards silkscreen for the Through-Hole crystal you can see one corn […]
Show full quote

NightShadowPT wrote on 2023-08-07, 15:44:

Bought both, just in case (they were 2$ each...) 😀

For the installation, do I just need to respect the "notch" orientation, solder, change the CPU and call it a day?

The 'dot' on the current SMD one indicates pin 1. And on the boards silkscreen for the Through-Hole crystal you can see one corner is not rounded which indicates pin 1.
So the green C in your picture is pin 1. Your new crystals should have a dot too to mark pin 1 so orient them the same way.

I've never owned a PC with a CPU Card so I don't know if it needs anything else, but I've done a crystal change to a NCR 486 Mobo and it didn't require anything else to work.

The not rounded corner also have a "*" silkscreened on the board.

Cheers,

Thanks for the tips... I'll let you know how the adventure progresses as soon as I receive the oscillators and try my soldering skills 😀

By the way, if you look at the board on the first post, you can see there is an empty slot for what looks like a Mathematical Co-Processor, but in this case it does not make much sense because the 486DX already has one... does anyone know what it's for?

Cheers,

NightShadowPT wrote on 2023-08-09, 06:05:

Thanks for the tips... I'll let you know how the adventure progresses as soon as I receive the oscillators and try my soldering skills 😀

By the way, if you look at the board on the first post, you can see there is an empty slot for what looks like a Mathematical Co-Processor, but in this case it does not make much sense because the 486DX already has one... does anyone know what it's for?

Cheers,

Presumably this...

If you are a beginner regarding soldering, here are a few tips:
- Use flux and dab a few drops of new solder on each leg before attempting removal
- Preheat the board. These should have a few inner layers which can have large copper planes (ground). Preheating it to even 70°C in an oven is better than not. Watch your fingers! And don't tell the spouse..
- Be gentle, take your time (unless you are using hot air).
- Practice on a donor board if possible

PC Hoarder Patrol wrote on 2023-08-09, 10:22:

Presumably this...

50M Weitek.jpg

Thanks, that clarifies it.

Now for the million dollar question.
I understand why you would want a 387 for a 386 processor... I know their uses are limited, but they exist, but if the 486DX already included an FPU, why would anyone need a 387 for?

oh2ftu wrote on 2023-08-09, 11:18:

If you are a beginner regarding soldering, here are a few tips: - Use flux and dab a few drops of new solder on each leg before […]
Show full quote

If you are a beginner regarding soldering, here are a few tips:
- Use flux and dab a few drops of new solder on each leg before attempting removal
- Preheat the board. These should have a few inner layers which can have large copper planes (ground). Preheating it to even 70°C in an oven is better than not. Watch your fingers! And don't tell the spouse..
- Be gentle, take your time (unless you are using hot air).
- Practice on a donor board if possible

Thanks for the tips... appreciated.

NightShadowPT wrote on 2023-08-10, 05:47:

Thanks, that clarifies it. […]
Show full quote

PC Hoarder Patrol wrote on 2023-08-09, 10:22:

Presumably this...

50M Weitek.jpg

Thanks, that clarifies it.

Now for the million dollar question.
I understand why you would want a 387 for a 386 processor... I know their uses are limited, but they exist, but if the 486DX already included an FPU, why would anyone need a 387 for?

It just states that the internal coprocessor in the 486DX or DX2 is compatible with a 387, probably obstruction set-wise.