486sx and 486dx

Discussion about old PC hardware.

486sx and 486dx

Postby Baoran » 2018-1-30 @ 15:25

I have a 486 motherboard which I don't know how to configure jumper settings for. It came with 486sx 33Mhz cpu and seems to work fine with the jumper settings that were set when it arrived in mail. Can I change that cpu to 486dx 33Mhz cpu without changing any jumpers?
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Re: 486sx and 486dx

Postby derSammler » 2018-1-30 @ 15:34

Normally, yes. No PC after the XT had to know by a jumper/switch whether an FPU is present or not.
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Re: 486sx and 486dx

Postby alvaro84 » 2018-1-30 @ 18:48

I often see different settings for SX and DX in 486 motherboard manuals. But I don't understand why. Whenever I was lazy and ignored these settings the system worked just fine.
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Re: 486sx and 486dx

Postby RobertJ » 2018-2-01 @ 19:07

Most of the time, just swapping the CPU will have the desired effect. Not too many games took advantage of the DX versus the SX, but those that did were amazing.
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Re: 486sx and 486dx

Postby badmojo » 2018-2-01 @ 20:02

RobertJ wrote:Most of the time, just swapping the CPU will have the desired effect. Not too many games took advantage of the DX versus the SX, but those that did were amazing.


Never heard if any game taking advantage of it, could you provide an example?
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Re: 486sx and 486dx

Postby derSammler » 2018-2-01 @ 20:06

There are very few. Sim City uses it for faster statistics calculation, and Quake doesn't even run without. Can't think of any other game that makes use of it but doesn't require a Pentium, which always had an FPU anyway.
Last edited by derSammler on 2018-2-01 @ 20:36, edited 1 time in total.
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Re: 486sx and 486dx

Postby Radical Vision » 2018-2-01 @ 20:17

Still no matter what the SX is like D class car, while DX is like S class car...
The d class will do the job fine, but the S class have premium feeling, that is why everyone wants S class not D...
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Re: 486sx and 486dx

Postby Baoran » 2018-2-01 @ 20:18

I guess the motherboard doesn't care which cpu is installed because in the table before booting it says "80486dx or 80486sx". I found jumper settings online for very similar motherboard online, but actually the jumper that is suppose to set either sx or dx is missing from my motherboard, so perhaps my motherboard is different revision or something.
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Re: 486sx and 486dx

Postby derSammler » 2018-2-01 @ 20:28

Radical Vision wrote:Still no matter what the SX is like D class car, while DX is like S class car...
The d class will do the job fine, but the S class have premium feeling, that is why everyone wants S class not D...

Everyone wants the DX probably because it's the real 486, whereas the SX is gelded. In the first two years of the 486, there wasn't even a SX. (and no DX either, as those monikers were introduced in 1991 with the SX)
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Re: 486sx and 486dx

Postby vladstamate » 2018-2-01 @ 20:33

Radical Vision wrote:Still no matter what the SX is like D class car, while DX is like S class car...
The d class will do the job fine, but the S class have premium feeling, that is why everyone wants S class not D...


Not for 486 it isn't. Like people mentioned before unless you play Quake, you would not see any difference between an 486SX 33Mhz and 486DX 33Mhz.

386 SX vs DX, that is a different question.
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Re: 486sx and 486dx

Postby Baoran » 2018-2-01 @ 20:54

Most people here seem to just build high Mhz 486 systems. I usually just think about what I want to do with the system. I had originally planned building a 33Mhz 486dx system before I even got the motherboard and I had the 486dx cpu ready for it. in the early 90s I pretty much skipped 486 completelly. I went from 386 33Mhz to Pentium 90Mhz. 486 33Mhz seems be the most flexible system in my opinion when it comes to compatibility with dos games.
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Re: 486sx and 486dx

Postby Azarien » 2018-2-01 @ 20:56

vladstamate wrote:Not for 486 it isn't. Like people mentioned before unless you play Quake, you would not see any difference between an 486SX 33Mhz and 486DX 33Mhz.


Quake is playable only in low resolutions like 320x200 on a 100 MHz 486DX, I can't imagine playing it on a 33 MHz, though technically it should run.

I remember that I did make a lot of use of the FPU unit in my 486 (like 3D raytracing, some video watching) but who would use a 486 for such tasks today. Not fun.
And that was a 100 MHz.

But if I had a choice, I would take the DX version, of course.

If you replace an SX with a DX, just make sure it works as it should, e.g. try to start Quake and watch the slideshow :-)
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Re: 486sx and 486dx

Postby Baoran » 2018-2-01 @ 21:07

How much ram quake requires?
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Re: 486sx and 486dx

Postby Scali » 2018-2-01 @ 21:09

badmojo wrote:Never heard if any game taking advantage of it, could you provide an example?


Falcon 3.0 had an enhanced mode if you had an FPU.
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Re: 486sx and 486dx

Postby vladstamate » 2018-2-01 @ 21:38

Baoran wrote:How much ram quake requires?


I can run Quake on a 486 DX2 66Mhz with 20Mb of RAM at 5.6FPS (time demo).You might be able to run with 4Mb only.
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Re: 486sx and 486dx

Postby badmojo » 2018-2-01 @ 21:59

Scali wrote:Falcon 3.0 had an enhanced mode if you had an FPU.


You learn something new every day, I always thought it was just CAD, etc that used it during the 486 era.
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Re: 486sx and 486dx

Postby leileilol » 2018-2-01 @ 22:10

Buying a 387SX/DX benefited Falcon 3.0 over a 386SX/DX as well.

vladstamate wrote:You might be able to run with 4Mb only.


Quake requires 8mb minimum as well as a FPU. elainda ran it on a 387 once.
Last edited by leileilol on 2018-2-01 @ 22:11, edited 1 time in total.
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Re: 486sx and 486dx

Postby appiah4 » 2018-2-01 @ 22:10

derSammler wrote:Normally, yes. No PC after the XT had to know by a jumper/switch whether an FPU is present or not.


Not true, I have 486 boards that have SX/DX jumpers.
1989:A500R6|+512K/RTC|ACA500+|HxC/df1:|C1084S
1992:HIPPO-VL+|DX2ODPR66|8M|GD5428|CT2290
1995:PCI597-1|P133|32M|Trio64|Voodoo1|CT3980/2M|DreamS2
1998:S1573S|K6-2/400|64M|RagePro|Voodoo2/SLI|CT4500/32M
2001:GA-6OXT|PIII-1200|512M|GF3Ti200|MX300
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Re: 486sx and 486dx

Postby derSammler » 2018-2-02 @ 10:00

Show please. And what happens when setting the jumper wrong? Since the FPU is internal and can not even be switched off, what the heck are those jumpers supposed to do anyway? They may just alter the CPU detection string...
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Re: 486sx and 486dx

Postby Scali » 2018-2-02 @ 10:15

derSammler wrote:Show please. And what happens when setting the jumper wrong? Since the FPU is internal and can not even be switched off, what the heck are those jumpers supposed to do anyway? They may just alter the CPU detection string...


Perhaps this is one of those boards where the 486SX is soldered on the board, and there is a '487' socket? In which case the jumper selects whether the board uses the 486SX or the 487 in the socket?
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