Iirc I only have a single Socket 5 board and it's an Intel one, which means the lowest FSB I think would be 50MHz?
Also I "think" my particular board doesn't even have any cache on the motherboard, but I'm not sure about that as it's been a couple years since I last handled that board. And the board would only officially support Pentium non-MMX up to 120MHz or so? Of course I could probably still plug in a Pentium MMX overdrive for 200MHz but all in all, it never got past the "what if"-stage.

I agree though that theres virtually no Socket 5 love but part of that might be because those boards were in no way awesome and pretty hard to find, even when the stuff was dumped on the streets for free (I found 2 Socket 4 boards in that same time frame).

It is possible on some boards to go even lower but those are hidden or unknown settings plus they are very stable.

I have an Asus socket 7 board that lets you downclock the FSB to the ISA buss clock speed.
Its a undocumented setting, I found it while looking for an undocumented 83 mhz setting.

Stability at ~8-10 mhz FSB was bad if remember correctly.

Skyscraper wrote:

I have an Asus socket 7 board that lets you downclock the FSB to the ISA buss clock speed.
Its a undocumented setting, I found it while looking for an undocumented 83 mhz setting.

Stability at ~8-10 mhz FSB was bad if remember correctly.

Skyscraper...can you please elaborate and provide details on how you downclock and for what model of board you can do that to?...that sounds very interesting to me as I have a few Socket 7 boards where I would love to be able to do that!

Skyscraper wrote:

I have an Asus socket 7 board that lets you downclock the FSB to the ISA buss clock speed.
Its a undocumented setting, I found it while looking for an undocumented 83 mhz setting.

Stability at ~8-10 mhz FSB was bad if remember correctly.

I can vaguely remember having underclocked a Socket 7 board by a lot and formatting a harddrive would be very slow until it would lock up after half an hour or so? Increasing the settings to normal speed and it formatted perfectly fine.

Btw I haven't a clue what board I tested this with, this was over 5 years ago.

As for why I have no love for socket 5 boards...http://web.archive.org/web/20070504165927/htt … b/CS-001826.htm

I find that socket 7 boards are better because of what is explained in the link above and that they are more readily available.

Having the option on a socket 7 to go with a 3.3v cpu (thus reducing heat) is an advantage as well as having the option of using an MMX enabled chip (if I use windows 3.11 or other windows versions).

Still...if I ever found a Socket 5 board for a good deal, I would not pass it up, but I pretty much would not pass up any retro hardware if the price is right. 🤣

EDIT: but I do see the benefit of the ability to downclock further as you mentioned...it's just that you might as well have a seperate older system if you have to downclock that much further.

retrofanatic wrote:

Skyscraper wrote:

I have an Asus socket 7 board that lets you downclock the FSB to the ISA buss clock speed.
Its a undocumented setting, I found it while looking for an undocumented 83 mhz setting.

Stability at ~8-10 mhz FSB was bad if remember correctly.

Skyscraper...can you please elaborate and provide details on how you downclock and for what model of board you can do that to?...that sounds very interesting to me as I have a few Socket 7 boards where I would love to be able to do that!

The board must have been my Asus P/I-P55TP4N.
I tested all combinations you can set the FSB jumpers to and one setting resulted in the board working in slowmotion.
It was extremly slow, if I remember correctly the keyboard stopped working after a while and I did not investigate much more.
My goal was to find undocumented higher than stock FSB settings, not lower 😀.

This may very well be the MOBO in my Pentium 133 at the time. I upgraded it with a new MOBO and Pentium 233MMX later on.

My favorite PC of all is my Socket 5 Vectra XU 5 😀
I wonder what kind of processor could i use in it thats not from Intel. It supports 66MHz FSB.

Tetrium wrote:

Iirc I only have a single Socket 5 board and it's an Intel one, which means the lowest FSB I think would be 50MHz?
Also I "think" my particular board doesn't even have any cache on the motherboard, but I'm not sure about that as it's been a couple years since I last handled that board. And the board would only officially support Pentium non-MMX up to 120MHz or so? Of course I could probably still plug in a Pentium MMX overdrive for 200MHz but all in all, it never got past the "what if"-stage.

Depends what kind of chipset you have, but some 430NX boards supported 2x multiplier and thus could run the P133. Other boards were multiplier locked and could only change FSB speed. No cache? Are you sure? Havent seen an Intel board without some cache on it.

I've identified two boards that officially supports 40mhz FSB:

- ASUS PCI/I P54SP4 (SIS 50X chipset) - Released in late 1994. This board have BIOS controlled PCI clock (44mhz, 40mhz, 33mhz and 14mhz) along with a much wider array of cache and memory settings compared to the Intel chipsets. I'll publish some performance graphs from this board later, but preliminary testing shows you can slow this board down to 486 DX2/66 speeds with turbo activated, and DX-33 with turbo deactivated. With L1 deactivated it goes down to 386 DX16-20 speeds with the same settings as above. From there you can tweak all the way up to Pentium 100 with overclocked PCI bus which gives a nice performance boost. It have the full array of settings for whatever you want. Want 486 DX50 equviliant speed? Then that is no problem by just changing some BIOS settings (and maybe change one FSB jumper). On a Socket 3 you would have to change CPU and/or reconfigure the whole board with a massive amount of jumpers. I haven't seen a Socket 7 board give the same type of flexibility in the whole range of 386 and 486 performance like this Socket 5 board offer.
- ASUS PCI/I P54TP4 (Intel 430FX) - Asus's first 430FX board released in early 1995. You could get 256/512KB async dip cache or 256kb Pipeline Burst hardwired on the board. AFAIK this is the first board were PB was offered. I have the version with 512kb async cache in DIP sockets. Quickly replaced with the P55 counterparts which had higher multiplier support (Socket 7).

Skyscraper wrote:

The board must have been my Asus P/I-P55TP4N. I tested all combinations you can set the FSB jumpers to and one setting resulted […]
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The board must have been my Asus P/I-P55TP4N.
I tested all combinations you can set the FSB jumpers to and one setting resulted in the board working in slowmotion.
It was extremly slow, if I remember correctly the keyboard stopped working after a while and I did not investigate much more.
My goal was to find undocumented higher than stock FSB settings, not lower 😀.

Thanks...I don't have a TPN4 unfortunately, but maybe setting the FSB similarily in my TXP4 or TX97-e board will offer the same result.

vetz wrote:

So guys, why do people not use Socket 5 motherboards in your retro systems?

Probably because socket 5 boards aren't as easy to find as socket 7 and those who go the socket 5/7 route usually go with Super 7 boards so they can run the fastest AMD chips.

sliderider wrote:

Probably because socket 5 boards aren't as easy to find as socket 7 and those who go the socket 5/7 route usually go with Super 7 boards so they can run the fastest AMD chips.

I agree that they aren't as easy to find as Socket 7 boards, but when did that stop people on this forum to get what they wanted? A good 486 PCI board isn't easy to come by either (and certainly not cheap!). Socket 5 boards are rare, but still very affordable 😀

For me it is dawning that a flexible Socket 5 or 7 is the route to go along with a quick Pentium III system. In terms of flexbility I mean even more than what for instance Mau1wurf1977 SS7 Ultimate DOS system can offer. A quick AMD CPU in a SS7 board does not offer same amount of flexibility to slow the system down and it is not quick enough to run games like Unreal in good enough FPS. It falls between two chairs. A Socket 5 system will normally cut off at Pentium 100 speeds (unless you install an Overdrive or Powerleap) which is about 1995/1996 in terms of gaming. From this point in time a Pentium III runs the games fine.

vetz wrote:

Havent seen an Intel board without some cache on it.

I have a cacheless Socket 7 "Zappa" board.

On topic, I don't know one single game that would need exact DX4-100 speed.

retrofanatic wrote:

Thanks...I don't have a TPN4 unfortunately, but maybe setting the FSB similarily in my TXP4 or TX97-e board will offer the same result.

Doubtful it will work. The TPN4 is using the Intel 430FX chipset. The boards you listed are using newer chipsets.

Same reason people don't love the early 486 boards, they cannot run the top of the line CPU in one.

Personally if you want to run an early Pentium the rare Socket 4 P60/P66 are the way to go. Very unique setup that cost a mint when new.

Most of what you find in the wild (outside of a brand name system) is Super Socket 7 anyway, they made millions of those boards and you can run most anything in them.

I have a Millenium P100 system that runs an Optibase ISA video capture setup under Windows 95. Can't think of any other system I have that would be socket 5 (have a couple socket 4 and lots of later Pentium 1s).

I had a few socket 4 boards, but they seemed kinda useless with no processor for them.
My Socket 5 board has 256kB Motorola Burst-RAM MCM72BA32SG60.

Cache me mon

vetz wrote:

The biggest benefit compared to Socket 7 is the possibility to downclock even further and get full range of performance from 386 to Pentium 100 on the same CPU and little jumper swapping (compared to a Socket 3 board). As a pure DOS PC from 1995 and backwards I think a good Socket 5 board is better than a quicker Socket 7. The Socket 7 boards have a "hole" were the Intel DX4-100 is meant to be performance wise. This is covered on many Socket 5 boards thanks to manual PCI clock divider (available on SIS chipsets) and 40MHZ FSB jumper (and generally slower performance).

A socket 5 with a CPU-adapter basically makes it a socket 7. So one might wonder what is actually compared here. At least I do agree that the super 7 chipsets do not make the preceding chipsets obsolete. Mainly because are they lacking in reliability compared to the average Intel product.

Personally I don't have any AT (versus ATX) components, no 72-Pin RAM either. This has so far prevented me from going further backwards in time then Socket 7. Regardless, I always like reading about underclocking, and experimenting with it. So 40MHz FSB sounds great.

I also noticed this range gap above 486DX/2-66 speed.
Now, Feipoa wrote somewhere that the original Cyrix 6x86 had a rare 1.0x multiplier setting. Unfortunately the 6x86 is not that desirable, if only because it gets rather hot while doing nothing fancy. But I recently sourced a 6x86L PR200 split voltage model to try, and that one also supports the 1.0x multiplier reliably. At 60 MHz FSB SpeedSys says: 1.0x = 40 pts, 2.0x = 80 pts, 3.0x = 120 pts. That is easy enough to remember 😀. The point is that 40 pts equals a 486DX/4-100, at least in speedsys. It manages these 1.0x and 2.0x speeds at a mere 2,2 Volt. Disabling the L1 cache lowers the scores to around one third / one quarter IIRC.

Some 6x86L seem to mention only 3,3V on the chip, I wonder if these are still split voltage.
In addition I am still wondering if there are actual Pentium MMX chips that do 1.5x like the original Pentium, and how they are identified.

I have 5 complete socket 5 systems, just haven't had time to share pictures of them:

Packard Bell Pentium 75
Dell Optiplex Pentium 90
Dell Optiplex Pentium 100
Nec Powermate Pentium 90
AT&T Globalyst Pentium 76
Micron Pentium 100

I'm currently playing Doom 2 wads on the Dell Optiplex Pentium 100 with a Soundblaster CT2230 with ASP with a Roland SC-55 it is awesome.

I also have 6 complete socket 4 systems, 2 of which have FDIV bug. I love the Pentium classics.