The i486DX4 had a few features from the Pentium that the Am5x86 didn't. It had VME for better vm86 performance, and the write-back ones had PSE for 4MB large pages. Both require OS support to take advantage of, and Intel when they released them documented them in an NDAed book referenced in the infamous Appendix H. Execute the CPUID instruction on both with eax=0x80000001 and compare the output in the EDX register on both CPUs.

So basically their engineers tweaked things but the business guys wanted to sell the Pentium instead because it was the real gravy train.

Was there actually any difference in FPU performance between the AM486 and the i486? I thought they were pretty much copies.

btw, there were AMD DX4's with 16kb cache but the 8kb were much more common. Actually, the AMD DX4 came in 3 flavors:
8kb WT
8kb WB
16kb WB

I'm not sure if a 16kb WT model was ever made by AMD

So basically their engineers tweaked things but the business guys wanted to sell the Pentium instead because it was the real gravy train.

Yes, but they still wanted to sell the 486 too as a lower-end alternative. They BTW closed every system-level Pentium new feature in the NDAed Appendix H. Application-level features was not closed for obvious reasons.

Back in 486 days I actually used an AMD DX2-80 in my setup so I'm a little biased towards AMD. I got the AMD because it was faster and cheaper than any Intel chip I could afford at the time. I wanted to upgrade to the Pentium class AMD chip but a sweet deal on a Packard Bell P-150 system lured me into it's web before I could do the upgrade. I've got an AMD 133mhz now that I will build when I have time. If I am careful enough maybe I can unbend some of the pins on my ADZ stepping chip and get it rocking at 160mhz. At 160mhz that's faster than an 83mhz Pentium Overdrive and a 90mhz Pentium but not quite up to Pentium 100 speed according to everything I have been able to dig up about overclocking these chips.

sliderider wrote:

At 160mhz that's faster than an 83mhz Pentium Overdrive and a 90mhz Pentium but not quite up to Pentium 100 speed according to everything I have been able to dig up about overclocking these chips.

I'm curious to find out this for myself also, but like you it's about having time 😉
I will build these systems...when I finally get around to it

Yeah it's something that has been discovered by a zillion enthusiasts over the past 15 years. Google Groups gets you the answers if they're not on this forum (which they are btw 🤣)

Execute the CPUID instruction on both with eax=0x80000001 and compare the output in the EDX register on both CPUs.

Stupid mistake, it is actually eax=0x00000001, these CPUs are too old to have the 0x80000000 leafs.

5u3 wrote:

Better get a K6 for Socket7 systems, it goes all the way up to ~500 MHz.

Sorry for a bit of offtopic, but that's an interesting alternative, the Super S7 platform. It tends to have ~lots~ of ISA slots, like 3 or 4, which is just great for the sound cards.
and yes, it's up to 500 or 550 MHz.

But what of their AGP type, could you share some knowledge. Might you call VIA MVP3 a nice AGP set?

I remember they were not horrible at least. Do you know of any serious flaws?

Mithloraite wrote:

Do you know of any serious flaws?

The chipset on every SS7 mobo seems hit and miss; Mostly leaning toward miss. All my SS7s are dead.

Also a K6, you'd better freaking cool that thing. Mine ran 140f at idle.

Does it really matter much?

If you need something faster you will got with a Pentium or K6 anyway.

Old thread I know but I've been playing around with these chips and thought I'd add some benchmark results, might be useful to somebody.

Motherboard: ASUS VL/I-486SV2GX4
AM5X86 133: 48.24 in speedsys
i486DX4 100: 42.39 " "

I never saw a game released back then that didn't fly on a 486DX2-80. Probably as good as you will need for the time period. By time period I mean around the same time as Direct X was released, with games like Firefight and the demo for Diablo 1.

Some dos games around this period (such as Carmageddon or Quake) would not work on a 486, even if you reduced all the detail to minimum. Hence up to 1995 for the 486, and 1995 and beyond get the socket 7.

badmofo wrote:

Old thread I know but I've been playing around with these chips and thought I'd add some benchmark results, might be useful to s […]
Show full quote

Old thread I know but I've been playing around with these chips and thought I'd add some benchmark results, might be useful to somebody.

Motherboard: ASUS VL/I-486SV2GX4
AM5X86 133: 48.24 in speedsys
i486DX4 100: 42.39 " "

It's much faster at 160 😀 but that's not the point. I'm referring to real-world use at stock speeds

I had a 100 MHz 586 chip once...I was never really happy with it. It always seemed like an "in-between" chip - not really a 486, not really a pentium. I always had doubts about what it would really run, but on the other hand never really had a problem.

I'm playing around with a P75 now, and it looks good so far at a 40MHz FSB.
Though I'm not sure if I want to chance 50x3 since it's a bit of an overclock and the PCI bus would be even further out of spec.

A nice side bonus to that though is the increased memory bandwidth in a board with no L2.
😀