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Wanting to build a 486 system...need some advice.

itsvince725

Experienced Member
Joined
Nov 26, 2016
Messages
420
Location
Pennsylvania
I recently acquired a generic AT-class machine from the late 486 era. Fully loaded with Zip100, 5.25 floppy (1.2MB), 3.5 floppy (1.44MB), and CD, it's a great system.

The only issue is that at some point it was upgraded to a later AMD motherboard and now it's a K6 system. I want to turn it back to a 486 era system like it should be!

However I...I don't really know what would be the best option as far as CPU, and I'd need a motherboard to match. I was thinking AMD or Cyrix 5x86 for more oomph, but then I need a compatible motherboard and I haven't really found any yet.

Is the 5x86 worth it or should I just use a more easily available 486? I haven't found a DX4-compatible board yet but I'm sure they're out there.
 

mR_Slug

Veteran Member
Joined
Nov 28, 2006
Messages
874
Location
UK
It depends on what you mean by "486 era system like it should be". This is 1990 to ~1995. If you want a period-correct system, then the Zip drive would have to come out for pre-95 systems. As a rough guide:

1990-91: DX-33, ISA only, no CD-ROM, 5.25" FDD
1992-93: DX2-66, VESA local bus/ISA, possibly CD-ROM, no 5.25" FDD
1994-95: DX4-100, PCI/ISA, CD-ROM, no 5.25" FDD
1995- : 5x86 PCI/ISA, CD-ROM, no 5.25" FDD

This is a very general guide, there are always exceptions.

"Is the 5x86 worth it", yes its faster than a DX2-66. But its also true that the Pentium 133 is worth it, over a socket 3 5x86. And the Pentium Pro or K6 is better...

I think its probably better to just build what you want. Or if you want era-correct, pick a year and then see whats available.
 

Agent Orange

Veteran Member
Joined
Sep 24, 2008
Messages
6,069
Location
SE MI
I would recommend the AMD Am5x86-133 (Am5x86-P75 Socket 3) which easily OC's to 150 MHz. Try to find a 486 motherboard with at least 2 VLB slots, and if you located one with PCI, you've just hit a home run. I'm not a big fan of Cyrix although some here on this forum are. The 5x86-133 can give a P1 a run for its money in the right configuration and circumstances. Best DOS gaming rig out there for my money. Good luck with your build.
 

gepooljr

Experienced Member
Joined
Dec 8, 2012
Messages
153
Location
Las Vegas NV
The Am5x86-133 is the best choice. I have an extra board with the 133 processor, passive heat sink installed, memory and bracket cables. It is a later model UMC chipset with 3 ISA, 1 ISA/VLB & 3 PCI slots. Send me a PM if interested.
 

krebizfan

Veteran Member
Joined
May 23, 2009
Messages
5,331
Location
Connecticut
If you keep the K6 motherboard in a different case, I would suggest looking for a good DX4-100 motherboard. Changing motherboard multiplier and clock speed with jumpers can result in a system dropping down to 486-25 with many steps to the full 100 MHz speed. Easy to tweak to get the right performance for the specific game being run.

K6 chips can be slowed to 133 MHz which is roughly equal to 150 MHz 486 and turning off the cache and certain utilities could leave a very narrow gap in performance compared to the 486.

You will need to spend some effort finding a 486 motherboard that supports ATAPI making CD-ROM and Zip Drive usage easy.
 

itsvince725

Experienced Member
Joined
Nov 26, 2016
Messages
420
Location
Pennsylvania
It depends on what you mean by "486 era system like it should be". This is 1990 to ~1995. If you want a period-correct system, then the Zip drive would have to come out for pre-95 systems. As a rough guide:

1990-91: DX-33, ISA only, no CD-ROM, 5.25" FDD
1992-93: DX2-66, VESA local bus/ISA, possibly CD-ROM, no 5.25" FDD
1994-95: DX4-100, PCI/ISA, CD-ROM, no 5.25" FDD
1995- : 5x86 PCI/ISA, CD-ROM, no 5.25" FDD

This is a very general guide, there are always exceptions.

"Is the 5x86 worth it", yes its faster than a DX2-66. But its also true that the Pentium 133 is worth it, over a socket 3 5x86. And the Pentium Pro or K6 is better...

I think its probably better to just build what you want. Or if you want era-correct, pick a year and then see whats available.

1995 is the year I'm shooting for, and since the machine has this low budget "use what you got" mentality to it the Am5x86 definitely fits my needs. I've decided that's the CPU I want, so now I'll need to find a suitable motherboard. I know the 5.25 floppy isn't entirely accurate to 1995 but I would like to keep it, same with the Zip drive. Zip adds utility too since I can get a USB one and transfer lots of stuff to the system easily.
 

Anonymous Coward

Veteran Member
Joined
Aug 11, 2004
Messages
1,533
Location
Shandong, China
1995 is the year I'm shooting for, and since the machine has this low budget "use what you got" mentality to it the Am5x86 definitely fits my needs. I've decided that's the CPU I want, so now I'll need to find a suitable motherboard. I know the 5.25 floppy isn't entirely accurate to 1995 but I would like to keep it, same with the Zip drive. Zip adds utility too since I can get a USB one and transfer lots of stuff to the system easily.

If I were going to build a 486 for enjoying 486 era software, I'd go with an i486DX/2-66 and a VLB motherboard. The best chipset for that board type of board was the SiS 471. I think the UMC UM8498F was also a pretty good one. Honestly though, the 486 generation motherboards were all pretty solid, so anything with VLB should be decent for running a classic 5V 486. For 3V chips like the 5x86, you need to check that the motherboard has a VRM, or else you will need to use a special VRM module that goes between the CPU and the socket (they are not always cheap or easy to find).

Almost all PCI 486 boards have support for 3.3V CPUs. A lot of people who are building 486s these days prefer them because it is easier to get PCI cards than VLB cards. However, I feel that PCI boards do not properly represent what owning a 486 system was actually like in the early 90s. I prefer the older 5V boards. There weren't nearly as many 486 PCI chipsets as there were for ISA/VLB. Most of the ones made after 1995 were also pretty solid. UMC 8886F and SiS 496 are generally considered the better ones, but it really depends on the chipset revision.

One feature a lot of people seem to like on 486 boards of any type are PS/2 mouse ports. This is nice to have, but not easy to find. For VLB boards, I prefer AMIBIOS...but for PCI based boards, you should really try to get AWARD. MR-BIOS is better than either, but kind of rare.
 
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