you can try undocumented FSB jumper settings to see how low it can go. You might be able to get down rather low and then disable cache.

Both my Pentium boards do not go below 50MHz (documented or undocumented). They are one of those that only have four jumpers, therefore four combinations (50, 60, 66, 75) are possible. I've also googled the clock generator some time ago and apparently those are the only clocks they can provide.

Btw, the 486 I mentioned is a late one (bios claims a 1994 copyright), with ISA and PCI (no VLB visible) and a lot of stuff onboard. The shipping price is at about 6 dollars, which is an added bonus.

Get that 486 and you'll be more then fine for older games. If you want a 386, get DX and 33-40MHz. SX and lower clock speed feel really slow - too slow if you're not used to it.

If you are used to Pentium, just stick to pentium. In my experience unless you find a working 386 or 486 then they are WAAAAAAAAAY too much of a pain to get working. If it isn't corrosion on the mobo because of an exploded CMOS battery, then it's disk geometry HELL if it's not that then it's something else, maybe I've just had bad luck with these systems but Pentium machines are where it's at as far as I'm concerned. 🤣

I haven't had THAT much trouble with 486 boxes. Especially newer generation 486s. 386s will probably a little slow unless you want to run REALLy old games.
A 486/33>386/40

my pentium system has an deturbo Funktion (i think i have to press ctrl+alt+-for deturbo.

The system runs then (or emulates) a 386 with 8 Mhz.

There are software slowdown tools (MoSlo/Slowdown/others) that can make many of the games which normally are too fast on a Pentium run well. I think I even got quite a few of them to work on the K6-500 after sufficient slowdown.

Many, but not all. There are always those finicky games that will just refuse to work properly. Or the slowdown will be non-uniform / different than expected, causing other glitches. For some, there exist patches which fix them, for most there do not. For the latter games you may want a dedicated machine.

But there is (almost) no end to this. You may get a 486, then a few games won't be happy with anything over a 386. Then a few more will not be happy with anything faster than a 286 or (God forbid) XT. The question is - how many of these badly programmed games are in your collection and how many do you insist on playing on real hardware. For many of them it may actually be far easier getting them to run inside DOSBox.

If only all games were written properly to begin with... Think of Alley Cat. 😀

alexanrs

Do try to disable the internal cache and motherboard cache. And then you go from there. I think you can probably slow down your pentium to 386DX-33 or DX-40 level.

I've had good results with a downclocked 286. I crystal modded mine with an 8MHz OSCI and i could play a lot of pesky games that need an XT.

See how slow you can go with your Pentium. Check all games you want to play, and if its not slow enough then you plan a build. A Socket 7 machine and an XT should be enough for DOS games. Unless you want to play Test Drive III and you can't get it to proper speed on the Socket 7.

With a Pentium MXM, disable both caches and you have a 386DX, leave L2 enabled and you have a 486DX2 😀

kixs wrote:

Get that 486 and you'll be more then fine for older games. If you want a 386, get DX and 33-40MHz. SX and lower clock speed feel really slow - too slow if you're not used to it.

Thanks. I imagined an SX would be too slow for 386-era speed sensitive games... after all the DX was there at the same time, and I have a hard time believing games targeting a 386 wouldn't work on a DX. Guess the SX would be good for 286-era stuff, but then there is the turbo button.

King_Corduroy wrote:

If you are used to Pentium, just stick to pentium. In my experience unless you find a working 386 or 486 then they are WAAAAAAAAAY too much of a pain to get working. If it isn't corrosion on the mobo because of an exploded CMOS battery, then it's disk geometry HELL if it's not that then it's something else, maybe I've just had bad luck with these systems but Pentium machines are where it's at as far as I'm concerned. 🤣

That is one of the reasons I'm looking at this particular 486. It is already set up, in its case, with the battery replaced (so the owner probably knows a thing or two about old PCs), with LBA support and tested. Hell, it even comes with a fresh install of DOS 6.22 the owner did to test it. The case also looks nice, but I'm mad at myself for letting his 386 DX-40 slip through my fingers... the AT case wasn't a baby one, and it looked even better!

dr_st wrote:

But there is (almost) no end to this. You may get a 486, then a few games won't be happy with anything over a 386. Then a few more will not be happy with anything faster than a 286 or (God forbid) XT. The question is - how many of these badly programmed games are in your collection and how many do you insist on playing on real hardware. For many of them it may actually be far easier getting them to run inside DOSBox.

Wouldn't a 486 with L1 cache disabled be equal to a same clocked 386? Btw can someone disable the multiplier of a DX2? If so it could be turned into a 386DX-33. Also, I've seen on Vogons that some 486 with the turbo and caches disabled drop to 286 speeds.

carlostex wrote:

See how slow you can go with your Pentium. Check all games you want to play, and if its not slow enough then you plan a build. A Socket 7 machine and an XT should be enough for DOS games. Unless you want to play Test Drive III and you can't get it to proper speed on the Socket 7.

I do plan on getting a 4.77MHz 8088 system, as these seem to be cheaper than a 286 around here. Also I planned on doing a more in depht study on my Pentiums, but I won't have access to them until tomorrow at night, and even then I have plenty of assignments to finish so I probably won't have the time to do so until later this week. And seeing how fast his 386 sold (from when I found it to the date it got sold only a few days passed), I'm somewhat trying to hurry. Some people think low end retro stuff are made of gold, like US$ 100+ 386-SX bare motherboard with a battery that is obviously leaking and was tested over a year ago, and this seller's asking prices are VERY reasonable. This 486 is under US$66 including shipping. That is why I ask: are there enough good games that would run here (+ all the 486 hardware slowdown tricks) and not on a Pentium with caches disabled that would justify getting this cheap 486? Not necessarily games I already own, as I'm also expanding my collection.

Also, by doing some research I found out what board the system has. It look like this. Looks like a nice board that would support sub-5V processors (not that I think it is worth changing the DX2-66). It comes with a NIC and an ISA VGA, but I could easily drop a Trident PCI VGA there.... or not, as I could just use the Pentiums to run games that would benefit from faster vídeo cards.

alexanrs wrote:

Wouldn't a 486 with L1 cache disabled be equal to a same clocked 386? Btw can someone disable the multiplier of a DX2? If so it could be turned into a 386DX-33. Also, I've seen on Vogons that some 486 with the turbo and caches disabled drop to 286 speeds.

According to philscomputerlab's post above yours, it may actually be possible to emulate both a 386 and a 486 on a Pentium by selectively disabling caches. I never tried this, so I don't know how accurate it is, or whether any BIOS/mobo supports it. But it sounds promising.

The very same question that you're asking is one that I've been grappling with for years.

I think that most of the answers you were looking for has already been addressed but, just some comments on my own experiences over the years:

I also started out with a Pentium MMX 233 MHz, hoping to have one PC that would suit all my retro game needs, and quickly realised that, depending on what type of game (and the era) I wanted to play, a Pentium was sometimes just too fast.
Granted, over the years, many patches have been brought out by 3rd parties to address speed issues in games where the CPU was a Pentium or higher.

Being not a fan of emulators (although, they have become quite good), and the fact that I like to play around with the physical hardware, I've been experimenting with different types of CPU's over the years.
I have an AMD 486DX4-100 that I use as my main DOS PC but, also a Cyrix 486DLC-40 and an AMD 386DX-40 as two "backup" PC's.
The AMD 486DX4-100, in it's de-turbo mode, slows down to the same speed as a 486DX-33, which is suitable for practically all the games that I play but, this is sometimes still too fast to play games that were designed to run on 386 PC's (like Wing Commander 1).

I then experimented with cache "disabling" utilities, since I don't like to go into the BIOS to enable to disable the PC's L1 or L2 cache.
ICD & ICE is one utility but, this particular utility doesn't always work that well.
I then came across one called "Cacheoff" & "Cacheon" (it's contained in a zip file called "cacheoff.zip" but, I can upload it if you cannot find it).
This one works quite well (even on my K6-2 450 MHz) and doesn't cause any lockups.

Hope you find the right combination.

Attached the slowest speedsys core I could get out of the P54C on a Super Socket 7 mainboard: 9,79 points. I used Setmul to disable branch prediction and the V-Pipeline. As well as Caches of course. (This cannot be done a Pentium MMX, original Pentium only)
The second place went to the Cyrix 6x86L, using a 1.0x multiplier / 60MHz / no caches: 10,84 points in Speedsys.

On a 486 some games run to fast, Deathtrack for example. That can be solved by installing a 33MHz CPU model or running a Cx586 at 33MHz (1x) combined with using the De-Turbo function or disabling of the cache.

What makes me think the 486 can go where no Petium can is this thread, where the OP mnaged to slow down his 486 DX2-66 down to a 3.04 score in SpeedSys. The branch prediction thing, though, is new to me. Did not know that it could be disabled... Btw, why were you using it with a 60MHz bus instead of 50MHz?

alexanrs wrote:

What makes me think the 486 can go where no Pentium can is this thread, where the OP mnaged to slow down his 486 DX2-66 down to a 3.04 score in SpeedSys.

Yeah that is pretty neat. But on some 486's De-turbo is the same as disabling internal cache, and in that case these options cannot be combined.

alexanrs wrote:

The branch prediction thing, though, is new to me. Did not know that it could be disabled... Btw, why were you using it with a 60MHz bus instead of 50MHz?

It was done on a Super Socket 7 ATX mainboard, and as is typical with these late generation socket 7 boards; 60MHz is the mininum FSB speed.

I don't think branch prediction makes that much of a difference for very old games. But it slows a little extra. 😀

Well guys... YOLO! (God that sounds douchey)
Bought it, and will test slowdown techniques on my Pentium when I have the time. Even if I come to the conclusion that there is nothing I'd like to play that I can't do so with my S7 PCs, I'll just play around with it, like installing some dumb old version of Windows like 2.1/386 or 3.0 just for the heck of it.

Well guys, the 486 arrived and it is a quirky old system for sure!

• External cache doesn't work. Even using the slowest timings the BIOS offers, and even enabling SRAM waitstates. The cache chips might be busted. They are socketed, so they are easy to replace, though not important for what I want this system for.
• The processor socket is busted. This is the ony sad thing about this system... The DX2-66 is very firmly attached, though. So unless I want to experiment with other 486 processors, no big loss here.
• NO HEATSINK! Gosh, since it is an horizontal case I just grabbed an old 775 heatsink (with the retention clips removed) and I am now just leaving it balanced on top of the processor. Should I hunt for an actual 486 heatsink or just get some thermal adhesive and "glue" this on permanently?
• It slows down A LOT. I got it down to 2.13 in speedsys Oo
• It needs a sound card. Currently I have two ISA SBPro clones (one OPTi 82c929 - awesome clean sound - and one YMF719 - decent sound). I'm thinking of getting a CT1740 SB16, recapping it and, if the sound is good, put it in my MMX, replacing the OPTi sound card, and attach my DB50XG to it. If it is still noisy I could just put it in the 486. The reason I'm thinking of a CT1740 is because I'd like to avoid the hanging note bug, and i wanna replace that OPTi card (sutters if I have my SideWinder gamepad attached, perfect otherwise). What do you guys think?
• The case is awesome! My favourite AT case so far! It only has one issue (which isn't exaclty an issue)... You can screw things directly in the 5.25 bays, you need to attach some guides to the device, then slide it in. On the plus side this is awesome and feels very high quality compared to the cheap AT stuff I have, on the other hand I have an empty bay, a nice beige IDE CD drive and no way to attach it (without removing the 5.25 floppy drive). I could just transfer the floppy drive to one of the Pentiums (wich lack one of the bay covers anyway) and put the CD here, but I'd rather look around a bit and see if I can aquire such guides to have everything on the system. Were these standard at all? Or did each manufacturer use their own clips?
• For some reason this thing came undervolted. I set it back to 5V as soon as I noticed it.
• I have 16MB (2 8MB FPM sticks) installed, but the BIOS only sees 16000KB. If I put an extra 8MB stick (I have a set of four), it recognizes 16MB, but not more than that. Mixing with the two sticks that came with the system (4MB and 2MB FPM sticks, AFAIR) doesn't change a thing. No problem, but it is a weird quirk for sure.

Here are some pics!

- 486 on top of my Deskpro! The Deskpro needs a new front panel, though...

- The innards

- The 5.25 floppy drive and its retention clips

Now, some SpeedSys goodness:
- Normal run

- Turbo button off

- Internal cache off

- Both turbo and internal cache off

NO HEATSINK! Gosh, since it is an horizontal case I just grabbed an old 775 heatsink (with the retention clips removed) and I am now just leaving it balanced on top of the processor. Should I hunt for an actual 486 heatsink or just get some thermal adhesive and "glue" this on permanently?

A 775 heatsink without a fan is way more than enough for a DX2. You could go smaller even
I use a fairly small AM2 heatsink without a fan on my DX4-120 and it easily keeps it within safe temperature.

For some reason this thing came undervolted. I set it back to 5V as soon as I noticed it.

Just make sure it is a 5V chip.

I have 16MB (2 8MB FPM sticks) installed, but the BIOS only sees 16000KB. If I put an extra 8MB stick (I have a set of four), it recognizes 16MB, but not more than that. Mixing with the two sticks that came with the system (4MB and 2MB FPM sticks, AFAIR) doesn't change a thing. No problem, but it is a weird quirk for sure.[/q

384K bios area.
16000K is normal for 2x8

I don't know why it wouldn't go above 16 MB. It certainly should

It is an intel 486 DX2-66. AFAIK all Intel's 486 DX2-66 are 5V. I've googled a little before daring to set it to 5V though, just to be sure.