I bought (and still own) the dual 133 MHz Tyan Tomcat III and the dual 233 MHz MMX Tyan Tomcat IV a long time ago. While I agree there is no advantage in the DOS and Windows OSs from that time period, everyone forgets Linux was around and did. I started out with a Slackware install, and I compiled/upgraded my systems for years and years, including the aout to elf migration. Even after I migrated to a newer system for my desktop needs (AMD K6-III), my old Tomcat was the firewall/router for many years. Dual CPU help with interrupt processing which in an older system with fast NICs was a good thing. In 2000 or so I got the Asus P2B-DS (still have it) with 2x800Mhz Pentium III CPUs -- ran Windows 2000 and subsequently Windows 2003 on it. There was a a dual Tualatin Supermicro P3TDE6 (still have it) that followed for Windows 2003. On the desktop side next came the MSI-K7D and the Chaintech-7KDD (still have them) for dual Athlon under Windows 2000 then XP. Linux on all of these also as a dual boot or as servers. Dual CPU motherboards were very much part of my life in the 1990s and 2000s before multi-core CPUs became a thing. The only multi-cpu motherboard I am still using and/or working on as a project is a Tyan K8HM with dual AMD Opterons. It's useful because it sits in the middle of all the hardware transitions; it's 64 bit and has PCI-X and PCIe; I can do any of 10Gb, 8Gb FC, LVD SCSI, and HVD SCSI.

I really wanted one of those Tyan boards that had a daughterboard that let you stack 8 processors onto an "E- ATX" ish size board. Water cool it, and use it to heat my house. ^.^

I have most of those boards you listed, I have a fetish for dualies. Even if they are only for bragging rights. As for linux... Well, not to be "that guy" but linux and gaming are about as compatible as a mongoose and a cobra.

luckybob wrote on 2021-11-28, 07:41:

I really wanted one of those Tyan boards that had a daughterboard that let you stack 8 processors onto an "E- ATX" ish size board. Water cool it, and use it to heat my house. ^.^

I have most of those boards you listed, I have a fetish for dualies. Even if they are only for bragging rights. As for linux... Well, not to be "that guy" but linux and gaming are about as compatible as a mongoose and a cobra.

Back in the early 1990s I worked at a company where we scored an IBM 720 server. After they reworked the electricity for it, we ran it for a few years. It had a "Corollary" bus from what I remember and supported up to 6 x Pentium processors with a dual PCI and Microchannel bus. It has always stuck in my mind as they very definition of a Frankenstein server. The several rows of fast spinning scsi disks along with the rest of the electronics guaranteed a nice toasty temperature in the server room.

I like having a brag about my dual P3. It took years to complete I still experiment too.
It is an ABIT VP6 and it has had lots of updates for backwards compatibility.
Running 4x250gb SATA on RAID 0 has not snapped for months.
100mbit LAN is a 32bit PCI 3com parallel 3 so it doesn't hog CPU I did have gigabit but sometimes it'd get unstable .
2GB of single sided PC133 non-ECC SDRAM this collectable system also runs ECC server ram but is a tad slower at that.
128mb SiS 315 running on 4x AGP Sideband. (plain but ideal for my intentions)
5 port USB2 I switched off motherboard USB for it has 1 internal socket I plan to pair via Bluetooth to an in the making 5.24 bay stereo boombox to tell the world
built in speakers are not just for laptops and no stupid noise from analogue (with proper tweeters than some kids headphone job.)
A good creative soundcard has a heatsink, a reason for not using win2000 it has front panel support.
What do I use it for?
Chose windows XP than Linux as Linux doesn't like the SIL 3114 SATA and likes to use the disks separately disregarding RAID.
I didn't build it for gaming I built it for other retro uses.
Firstly the CPU power I wanted to see if it could encode standard DivX videos faster than a single P3. Was successful using encoder v4 Ideal for AMV but I now use windows media 9 encoder that its plain better; most pc's know Microsoft.
Secondly I like playing synthesizers so I use it to record scores and edit them.
Thirdly I like to play midi files through several tone banks at once and the large memory bank makes it easier with SATA for paging when recording gets a bit cumbersome.
I will probably get into gaming on it someday but not until i see something generation correct that's actually truly useful than half dead eBay stock.
Though I still use virtualization for CD-ROMs and DVD-ROMS I can make backups and burn them too so I can play my titles on my purpose built P4 gaming rig that needs an AGP 8X card someday. A photo of my dual P3 desktop just a peek https://archive.org/details/vp-6-musical
A true time taker over COVID lockdowns it stopped me going insane. Ridiculously cheap to build except the motherboard that was totally worth the overall value about 75% new old stock I quivered with the last eBay listing for a VP6 motherboard was upwards $1000 US. (Without damage)
I have my favorite brand keyboard Honeywell and a optical mouse over ps2 it handles all human peripheral i threw at it wireless and wired keyboards mice game controllers even Bluetooth ones, but i choose wired for less interference in subsystem.

last eBay listing for a VP6 motherboard was upwards $1000 US.

I call bunk.

There are 2 on ebay now for ~$150. (Still too expensive, imho)

Several years ago I bought an NOS dual Socket-940 Opteron server board (Tyan S2882-D). I always thought they were cool and couldn't resist the chance to buy one when somebody was blowing them out.
I put a lot of effort into managing the power use of that machine, including software undervolting/clocking of the CPU, fan throttling, and spinning down idle hard drives. I also avoided installing more RAM than it needed. The board supports two dual-core CPUs - and I have them, but up to now I've always just had one CPU installed.
I was tempted to install an 8400GS PCI card so that it could be used as a desktop, but instead I left it with the onboard ATI Rage XL nonsense running in text mode.
So it's like I have a super expandable platform that I've kept chained up.

I use it for a file server, most of the data is video files.
To economize the storage, sometimes after downloading video files I will want to recompress them.
It would be convenient to let the server do the recompression, and installing the 2nd CPU would make it twice as fast at this.
But it's so slow at video compression that doubling the speed still wouldn't be fast enough for the power it would use. It makes more sense to go turn on my gaming PC for those jobs, despite the inconvenience.
There could be situations where real-time transcoding would be cool - but again it's not near fast enough for that.
SnapRAID is CPU intensive, but it's only single threaded.

So I might not ever find a good reason to install the 2nd CPU.
Anything I need that machine to do, it's either amply powerful for already, or it's too weak for doubling the CPU to be enough.

I wonder how many dual CPU servers or workstations ever got fully populated during their useful (non hobbyist) life.
Both my dual PPro and Slot-2 machines came from eBay with singles installed. Of course I expanded them but by that time the CPUs were obsolete and cheap (maybe not anymore).

SETBLASTER wrote on 2020-06-30, 17:41:

So i have seen quite a few people making retro builds with dual pentiums. Dual core was supported more towards half of the windo […]
Show full quote

So i have seen quite a few people making retro builds with dual pentiums.
Dual core was supported more towards half of the windows xp era.

So far i have seen pictures of people building a a dual Pentium1 socket7 build for example with a Soyo 5th5 motherboard.
ANd i have also seen Dual pentium 3 boards socket 370, even on youtube you can see people building those.
And also dual Pentium2 or pentium3 slot1 boards taken from server machines and they build a pc with that.

But what is the purpose of building such machines? just cosmetics to show something that is not common for home use?
or is there a real benefit of building that for playing DOS, Windows3.1 and windows98 games?

I know dual CPU motherboards are kind of rare, i don´t see them very often online, but are those really worth it?

Short answer is hell no. Those exotic machines were only useful for productivity software, not gaming. I recently got a dual Opteron setup. It is complete overkill for any game it can run and actually incompatible with anything later you might think it should be able to run, having 4 cores and all. The big problem is that you can't stuff enough GPU in there to make full use of those 4 cores. But, it has AGP and I just got a HD3850 AGP. Technically, it runs GTAV. But you don't wanna play it like that. Most people don't luck into the best AGP card ever for $5 and have the luxury of putting it in a rig with a not-quite-adequate single core benchmark and call it "good". I really wish I had a 775 board with an AGP slot. It is a show pony, nothing more, and an odd one at that. Then you are limited by RAM too... You might as well have asked "Sun Ultra 60 for Retro Gaming?", 🤣
The bottom line is that no games from that era will ever make use of 2 CPUs. Any prod software that will will be practically vaporware at this point. What OS will you run that can use 2 CPUs? NT 4.0? XP, 🤣
I recently got a 8400GS PCI to put in my Coppermine 600EB. Ridiculous, yes, but the only way I am getting streaming video playing on a Coppermine PIII... With an overclock, of course.

I dunno if you'd get much further on 775, AGP boards maybe only support prescott. Though I guess you might give it the D for make benefit glorious forums of vogons.

BitWrangler wrote on 2021-11-29, 04:47:

I dunno if you'd get much further on 775, AGP boards maybe only support prescott. Though I guess you might give it the D for make benefit glorious forums of vogons.

There are i865 boards with AGP that support Conroe.
LGA 775 Motherboards with AGP Slots

HangarAte2nds! wrote on 2021-11-29, 03:23:

Short answer is hell no. Those exotic machines were only useful for productivity software, not gaming. I recently got a dual Opt […]
Show full quote

SETBLASTER wrote on 2020-06-30, 17:41:

So i have seen quite a few people making retro builds with dual pentiums. Dual core was supported more towards half of the windo […]
Show full quote

So i have seen quite a few people making retro builds with dual pentiums.
Dual core was supported more towards half of the windows xp era.

So far i have seen pictures of people building a a dual Pentium1 socket7 build for example with a Soyo 5th5 motherboard.
ANd i have also seen Dual pentium 3 boards socket 370, even on youtube you can see people building those.
And also dual Pentium2 or pentium3 slot1 boards taken from server machines and they build a pc with that.

But what is the purpose of building such machines? just cosmetics to show something that is not common for home use?
or is there a real benefit of building that for playing DOS, Windows3.1 and windows98 games?

I know dual CPU motherboards are kind of rare, i don´t see them very often online, but are those really worth it?

Short answer is hell no. Those exotic machines were only useful for productivity software, not gaming. I recently got a dual Opteron setup. It is complete overkill for any game it can run and actually incompatible with anything later you might think it should be able to run, having 4 cores and all. The big problem is that you can't stuff enough GPU in there to make full use of those 4 cores. But, it has AGP and I just got a HD3850 AGP. Technically, it runs GTAV. But you don't wanna play it like that. Most people don't luck into the best AGP card ever for $5 and have the luxury of putting it in a rig with a not-quite-adequate single core benchmark and call it "good". I really wish I had a 775 board with an AGP slot. It is a show pony, nothing more, and an odd one at that. Then you are limited by RAM too... You might as well have asked "Sun Ultra 60 for Retro Gaming?", 🤣
The bottom line is that no games from that era will ever make use of 2 CPUs. Any prod software that will will be practically vaporware at this point. What OS will you run that can use 2 CPUs? NT 4.0? XP, 🤣
I recently got a 8400GS PCI to put in my Coppermine 600EB. Ridiculous, yes, but the only way I am getting streaming video playing on a Coppermine PIII... With an overclock, of course.

For gaming multiple CPUs/cores only started mattering recently, and even then they don't scale particularly well. Gentoo Linux should be able to compile a modern prod environment with relevant/modern apps if one wants. For older apps one could go with NT4, 2K, or XP. NT4 is still one of my favorite OSs; it's light and uses very little ram. Issue would be finding a modern browser for it. Almost everything has now switched to 64 bit only. The interesting one to play with might be OS/2 eComStation; I don't know how it's browser support is doing -- my guess not well. OS/2 is interesting also because of the way it virtualizes DOS. I used to be able to play DOS games that wouldn't even run on bare metal DOS due to the processor speed being too fast.