Jumper JP3 and JP6 to 1-2. JP4 and JP5 to 2-3.

Yep, that's what they're set to and I get a score of 87 in topbench and all the other checks/tests showing a 50MHz chip 🙁

For reference, here are the benches I'm getting with the MHz settings noted in each pic.

It's almost like I'm getting a reverse effect (which only adds to the confusion):

Thank again for the help/insight here.

Check for "turbo" jumper. Maybe it needs to be closed.

Can you use any real sysinfo program? Like NSSI, CHKCPU, SPEEDSYS, ...

CHKCPU shows 50.3 MHz no matter what I set the jumpers to. Same with Speedsys.

Turbo is off (when on, the speed dramatically slows, as expected).

Could it be a faulty chip? Maybe I should try a 5V AMD chip instead, or another later model Intel? (this one I have is a SX-750)

Can you show a picture of a full motherboard? It almost looks like the clock generator isn't working correct.

The "vidmem" access time seems quite high. What GPU are you using ? I've got a pentium 90 machine which came with a really slow GPU that made it unable to play doom smoothly. Replaced the slow gpu with a decent one and everything was smooth. And under topbench the "vidmem" access time was really high too

You may only go x2 or x3 of your built in CPU, so dx2 50 or dx4 75 overdrive.

Regarding speed I have same problem with my tulip computer 😉 I added dx4 75 but it's fast as 33 hehe

Ref intel
The 50 MHz IntelDX2 OverDrive processor is de- signed to upgrade 25 MHz Intel486 DX microproces-
sor-based systems and 16 MHz 20 MHz and 25 MHz Intel486 SX microprocessor-based systems The 66 MHz IntelDX2 OverDrive processor is de- signed to upgrade 33 MHz Intel486 SX and DX microprocessor-based systems Table 2-1 illustrates the speed and pinout configurations for each

The 100 MHz OverDrive processors are designed to upgrade most 33 MHz Intel486 SX and DX micro-
processor-based systems The 75 MHz OverDrive processors are designed to upgrade most 25 MHz Intel486 DX microprocessor-based systems and 16 MHz 20 MHz and 25 MHz Intel486 SX micro- processor-based systems

There exist motherboards that allow you to set the bus speed either by jumpers (if the clock generator is installed), or by crystal oscillator. Can you see a 50MHz oscillator anywhere on your board?

Well, would you look at that!

50MHz crystal.

So what do I do now? Do I need a 66MHz crystal, or a 33MHz crystal, or a?

Here's the exerpt from the motherboard site. I'll check the paper manual when I get home this evening as well-

Processor: 80486SX/80487SX/80468DX/80486DX2

Processor Speed: 16/20/25/33/50(internal)/50/66(internal)MHz

Thanks a ton so far! making progress!

I'm also interested now since I have the same crystal and get average as a dx2 33 with my dx4 75.

But would it help with the speed issue?

Erik765 Do you have a built in CPU as me?

tabm0de wrote:

I'm also interested now since I have the same crystal and get average as a dx2 33 with my dx4 75.

But would it help with the speed issue?

I am pretty sure I told you in one of your threads that you could change that crystal to be able to run your computer at 33 MHz FSB and use a DX4-100 overdrive. I also told you it involved soldering if the crystal wasn't sockted and yours isn't. You ended up buying a DX4-75 overdrive though eventhough a DX4-100 overdrive would have worked fine at 75 MHz which I also told you.

If the crystal is changed for a 66 MHz one your DX4-75 will be overcloked to 100 MHz and it will improve your performance a bit, if the DX4-75 can handle running at 100 MHz that is. Getting cache modules to get some L2 cache will also help your performance as you have 0KB L2 cache at the moment.

Oh, ok sorry didn't see that 🙁

tabm0de wrote:

Oh, ok sorry didn't see that 🙁

I called the crystal "metal can close to the CPU" or something like that if I remember right. 😀

I'm also confident that except in the benchmarking program you use your computer is much faster than a 486 DX33 eventhough it runs at 25 MHz FSB and lacks L2 cache. I would think that its performance with the DX4-75 is between a 486 DX40 with L2 cache and a 486 DX2-66 with L2 cache in most tasks. 256KB L2 cache would make it at least as fast as a DX2-66.

Erik765 wrote:

Well, would you look at that!

50MHz crystal.

So what do I do now? Do I need a 66MHz crystal, or a 33MHz crystal, or a?

A 66 MHz crystal should get you 33 MHz FSB. As the crystal is socketed it's easy to change.

Awesome! I think I'll go that route to start with and see how it turns out!

I'll update the thread accordingly.

Thanks for the pointers and getting me a path to go down.

You should still look after changing your video card too, topbench says that you've got a trident video card which was a really cheap brand of video cards ... and many of their GPUs were really slow. A slow GPU definitely won't help to get performance. Like I said, it can decrease the performance by a huge amount like it did on my pentium 90 where doom was sluggish

It's actually a CL GD5429 ISA card. I think it's showing the trident listing there as that was just the system that submitted the comparison result.

There appears to also be DOS drivers for it. I'm not sure if they do anything, but they're not installed quite yet either.

I'll do some proper graphics benches once I have this all up and running 😉

As i said before i had the same problem when adding dx4 75mhz overdrive on my builtin 25mhz cpu.
I gave me a avrage as a dx 33 mhz and i was so sad. 🙁

BUT now im happy after help from the guys here i was able to install cache to my system and it preforms as it should now! x2!!! and some peoples said it wouldnt be that much different 😉

So install cache and you could get dx2 50 mhz or dx4 75mhz or upgrade the crystal if you want the other models if thats how it works, i dont know about that part.

I hope you have the same problem as i did on my old tulip computer.

More info:
[UPDATE 4 / DONE] The journey of Tulip Vision Line DC 486sx TC35