You know, I guess starting on the more humble end, your usual suped up Win98 PIII machine. Starting in 1994 is really a saving grace, because I'm pretty sure there isn't a ton from 1994 onward that is speed sensitive? Although going through a list on the Vogons wiki there are more than I thought there would be.

I donno, if you really care about the speed sensitive games, I'd say go with a K6-II+ (or III+ if you can find it), and take full advantage of it's flexibility with setmul. But then you sacrifice a lot as you try to fill in the gap with the second machine. By 1999 whether they can run a game at playable framerates, by modern or contemporary standards, is really hit or miss.

So assuming a suped up PIII with say, a Geforce 4, that can handle things at playable enough framerates through 2003 or so, filling in the gap I'd go with an WinXP rig running a Core 2 Duo and a Geforce 8800 GT. Might not be optimal, but I built one in 2007, and it lasted me well past 2010 managing most games at playable framerates. Eventually I upgraded just the GPU a GTX 560 Ti in 2011.

You know, even if I went with the K6-II+, I think I'd still go with that Core 2 Duo/GF 8800 GT machine to stretch to 2010, versus looking back and trying to fill the gap created by choosing the K6-II+ over the Pentium III.

1. DOS and Windows 98SE
S478 Pentium 4 3.2 or 3.4 EE on a PIAGP system (AGP, PCI, ISA)
AGP Geforce FX 5950U (this is still CPU limited on this platform)
PCI 3dfx Voodoo 5-5500
SLI 12MB Voodoo 2
PCI sound cards would be Audigy 4 Pro and Aureal Vortex 2.
ISA sound cards... Not exactly sure what I would use.. Probably a few different ones with onboard wavetable as well as an Intelligent MPU-401 card.
AWE64 Gold with 24Mb upgrade would be one of the definite ones.

I have everything for the above build except for the V5-5500 PCI.

2. XP
Intel x79 based motherboard with a Xeon 1680v2 (best single socket CPU for that platform... unlocked as well).
3-way SLI 780Ti or SLI 980Ti or SLI Titan X or Quadro M6000 GB 24GB
Original PhysX card
Separate card for newer PhysX titles
Audigy 4 Pro or some X-Fi sound card.

Have everything for the above build except for working out the video card situation.

I could care less about period correctness... This is basically about the fastest possible with full support for the OSes mentioned.

Edit: I was gaming and building/upgrading computers as well as overclocking starting in about 1992. Was always on the hunt for that last bit of speed in pretty much every system I built for myself though I was on an extremely tight budget back then because I was too young to have a real job before about 1997. Even after I got my first real job, I was still buying the lower priced and used stuff as the massive price increase for the newest stuff could not be justified.
Now that I am older and have been able to acquire a bunch of top tier hardware from back then for usually next to nothing it is much easier to build systems I could only dream of back then.

spanning 1994 to 2010 actually makes things easy if we allow ourselves the use of

Dosbox
GOG
and a VM as an option

then for almost any game or application i'd care to run there is a way of doing so on just one 2010 specced machine

but to get that experience i'd go for the below, and i'm trying to be reflect my own modest budget/requirements here - no dream machines:

1) a later athlon xp or late P4 with Win XP, and dual boot 98se, along with reasonable graphics card, 1gb ram
2) 2010 is when the i5 CPUs were around so a machine with one of those (or a fast dual core is ok too) plus even a modest 1gb ddr3 graphics card and about 4gb ram with Win 7

of course machine #2 needn't actually be from 2010, it could be current, but i thought it would be fun to restrict it a bit

sure there's no ISA on #1 and we might have cpu speed problems etc but we're spanning 1994 onwards and those few remaining games around the edges of DOS still having problems will likely run just great in dosbox on machine #2 anyway

infact thanks to dosbox and gog almost any older game will run just fine on machine #2, but machine #1 with its win xp and win98se dual boot would cover off anything missed by gog and dosbox on #2

meanwhile even modest little machine #2 would be fine for GTA4, Far Cry2, fallout new vegas, borderlands and a bunch of other late 2000's games

if we spanned back to the late 80's though, and couldn't find a wanted game on GOG, we'd end up struggling with VMs or wanting a 3rd PC, a nice early pentium or some such!

and of course, this isnt how i do it - i have too many machines 😀

Yes, this is a challenge...
...trying to cover a) the 16-32bit era of 1981 to 1994 and b) the 32/64 bit era from then on to ~2010 in only two computers, to have the real feeling with real hardware.

a)
I built a potentiometer-controlled oscillator 2-33 MHz for 486, in a 5.25" cage, with nifty speed display that showed the actual CPU speed. This worked well with some restrictions that made me abandon this approach: floppy and soundcard DMA failed below 8MHz, so no booters possible. And only AMD processors accepted being clocked down to 2MHz, while Intel processors crashed at around 16 MHz. Occasional hangs/crashes when adjusting CPU speed on the running computer were annoying, too.

So I looked further and found in the SiS 496/497 "green" chipset data sheets a very nice detail: two 8-bit counter registers with which one can set/release the STOPCLK CPU pin depending on those registers, allowing for very fine grained speed control.
This can (hopefully, as my mobo has a late B4 chipset revision) be abused for slowing down an Am5x86-P75 down to 520kHz. With additional measures like cache off, DRAM speed control etc it might be possible to slow down waaay below original PC speed.
So this will be my only remaining real "retro PC".

b)
For later games and running processor speed-independent games I think I will use the DFI HD620-H81 mobo together with 4GB RAM.
The ISA slots are not practically usable for DOS gaming, but the board has 4 PCI slots, which is rare on modern mobos.
So, for compatibility some old cards can be used (for which DOS/Win98 drivers are available): Nvidia PCX 5750, Terratec Xlerate (Aureal 8820), Adaptec AUA-4000 (NEC USB chips), Intel Pro 1000GT. The 4th and last PCI slot is reserved for the Yamaha YMF724, in case it turns out to be possible to configure both sound cards that way that the Aureal 8820 with its "unusual OPL" does the sound and the YMF does the music.

Using setmul and cpuspd allows for some nice speed control with which the gap between both machines should be small, if any.

I would start with a SS7 machine that have a K6-III+ 550, CL5446 for Dos compatibility and Voodoo2-SLI for more demanding Win9x games.
For the high end machine that can handle games from 2001 to 2010, then I would build the meanest and baddest WinXP machine possible.
The good part, is that this WinXP machine, might also be fully Win7 compatible with enough umpf to go around.

However... I have no idea on what to use for the baddest and most mean WinXP machine.
I stopped gaming new games on computers from around 2006 and in 2008 I became a father.
In 2014 I went back into computing as a hobby, only to take up vintage stuff and not modern gaming. (That is why I have a Playstation3)

Windows XP Retro PC: Intel i3 3250, Asus P8B75-M LX, 8GB DDR3, Sapphire Radeon HD 6850, Creative Sound Blaster Audigy

Windows 9X Retro PC: Intel E5800, ASRock 775i65G r2.0, 1GB DDR1, AGP Sapphire Radeon X800 Pro, Creative Sound Blaster Live!

I have these two machines and I'm honestly super happy with them for covering Win9X and WinXP gaming, 😀

I am also no CGA/8088 freak, so also a 486 and P3 are good. But in reality I use a P1MMX for that authentic DOS/Windows 3.11/OS/2 1.3 2.1 experience. And a P3 machine for fast late DOS gaming and Windows 9x experience. You can slow down a P1 to 486/386/286 speeds. Even the P3 BX PIIX4 has a hardware throttle command, so no need for any software slowdown. I have many 486 computers, but really do not use them in day to day retro stuff, because a P1 can do all that a 486 can, but faster if needed.

(I assume these are retro builds and therefore I still have my modern PC)
Via C3 for 80s through to 1998, AEW64Gold+Audigy2, V2SLI+Savage4Pro, Win98SE.
Athlon XP 3200+ for 1999-2003, Vortex2, FX5950U, Win09SE.
2004-onwards, my modern build can handle with tweaking if necessary.

DOS/Win98 (1994-2001)

AthlonXP + an ISA capable KT133A motherboard, GeForce4 Ti + Voodoo2, Yamaha Audician32 and an Audigy2 ZS. When using ACPI Throttle and/or disabling the caches, this system can be slowed down to early Pentium, 486 and 386 speeds as needed. The GeForce4 is enough to max out most Win9x games at 1280x1024 while the Voodoo2 is only there for Glide compatibility. The Audician32 provides SBPro + WSS compatibility, genuine OPL3 and a bugfree MPU-401 in DOS. The Audigy2 ZS can give you some SB16 compatibility in later DOS titles, soundfonts for General MIDI as well as EAX support for Win9x games.

WinXP (2002 - 2010)

Intel I5+ whatever motherboard has fully functional WinXP drivers, GeForce GTX 750Ti and a Sound Blaster X-Fi Titanium PCI-e. For XP gaming, you want EAX, and the X-Fi Titanium is the best card for that. You also want a GPU that can push 60+ FPS at 1080p. The 750Ti should be capable of that in most games from 2010 and before, while still being able to use earlier Nvidia drivers which have some features that later versions removed, such as proper aspect ratio scaling.

For DOS and early Win9x (up to DX7 games):
Ideal choice: SS7 MB with K6-III+, 512 MB RAM, Voodoo4 4500, SB AWE32 or 64, 40-60 GB HDD + CF/IDE adaptor, CD-RW
Acceptable choice: S370 MB with Coppermine P3, GF3/4 or R9x00, SB Live or Audigy, 40-60 GB HDD, at least one USB flash drive with Win9x driver, CD-RW

For WinXP (DX9) to some modern games/apps:
C2Q to Ivy Bridge with corresponding MB, 2+2 GB DDR2/3 RAM, GTX 750Ti, SB X-Fi, 120 GB SSD

It's exactly this time frame I've set up my two most used retro/nostalgia PCs with a KVM switch.

For mid-90s to about 2002.
Tualatin S 1.26GHz
512MB 133MHz SD-RAM
MSI Geforce 4 Ti 4200 64MB
Creative Sound Blaster Live! SB0100

Its two main weaknesses is DOS sound for the earlier parts of its time frame and the lack of Glide support. Sadly the Compaq workstation motherboard doesn't have any ISA slots.

For 2002-2010.
Core2 Quad Q6600
4×1GB DDR2 800MHz
Geforce 8800GT
Sound Blaster X-fi SB0460

Its two main weakness is the underpowered GPU for the end of its time frame, I'm thinking about upgrading to a GTX460 to keep it close to period correct, the other is the lack of a dedicated PhysX card, but that was more of a gimmick than anything else.

Dos/Win9x
M/B Slot 1
CPU: P3 600Mhz or faster
Video: GF4 Ti
Video: Voodoo 2 SLI
Sound: Audigy 2 ZS
Sound: <insert your favorite ISA card here>

Speed sensitive games are an issue but I don't have many and Slot 1 holds nostalgia for me
D3D, Glide, EAX are all supported in windows and dos get's it's true ISA card.
And yes I own 2 rigs with very similar specs to this.

WinXP
M/B: S775
CPU: Something fast and cheap
Video: GF GTX590 x2
Audio: SB X-FI SB0880

Also own this build, GTX590's are overkill and could be stepped back a bit. Anything that runs in XP I can max out the details and they are still basically idling 😜
For the time frame you should be able to pick up a cheap S775 CPU's that's up to the task I got my x3320 2.50Ghz for $0

This is basically my retro set up as I don't like my retro PCs taking up too much space.

I have a 450MHz P3 for 98 and DOS duties with my AWE32 and pretty much any post 2000 AGP video card, like an MX card. It wouldn't be that fast for Windows 98 but it would be for games up to 98 as later games tend to be fine on XP.

Then a Socket 775 XP PC with a Core 2 Quad 3GHz, 4GB RAM and a late XP card like a 560ti. I'd stick an Audigy 2 ZS in there too for EAX duties. It was boot XP or dual boot XP and 7.

It works fine for the games I'm interested in.

I’m beginning to think it’s mighty unfair to only limit ourselves to just two builds in this timeframe. Three or four on the other hand…

pixelatedscraps wrote on 2021-10-22, 02:08:

I’m beginning to think it’s mighty unfair to only limit ourselves to just two builds in this timeframe. Three or four on the other hand…

You are right, the Macs shouldn't be forgotten.
But, when I played a bit with my last Mac today, an annoying fishy smell filled up my flat.
I guess I'll get rid of it. (Or just ban it into my basement, where it can stink happily)

yeah dont forget macs. just ignore them 😉 jk jk

pixelatedscraps wrote on 2021-10-22, 02:08:

I’m beginning to think it’s mighty unfair to only limit ourselves to just two builds in this timeframe. Three or four on the other hand…

Yeah, I think two well-built system is just about able to cover everything from the mid-80s to 2010, but not ideal. I think the two tricky points are early-to-mid DOS speed sensitive stuff and covering the Win98-XP switch without sacrificing late-XP performance. The Athlon XP can cover the Win9x/XP switch, but I don't know how much it can be slowed down. For XP however any E8000/Core2Quad or Phenom II CPU works.

Approaching from the other end, and covering DOS and early Win9x with a K6-III+ based build is good, but then having something that has compatibility with late Win9x and sufficient performance for late XP is the Achilles heel. You have options for motherboards with support for Win98SE, dual-core CPUs and PCI-e to have enough late XP performance, but then you have to entrust late-W98 graphics to a PCI card which will never be ideal. Or you go for the fastest possible W9x compatible GPU (X800XT I think), but for late XP games it just wont perform. The lack of SM3.0 support means no UE3 games for you. And for late XP you'd want 4GB RAM which is also dodgy with W98.

The ideal is probably 3PCs. A 486 for DOS, an Athlon XP or Tualatin for Win9x and a Core2 or Phenom II for XP.

RandomStranger wrote on 2021-10-22, 06:38:

The Athlon XP can cover the Win9x/XP switch, but I don't know how much it can be slowed down.

Pretty well using ACPI Throttle on a VIA chipset. As mentioned before 386, 486 and early Pentium speeds are all achievable on that platform. For best results, you want one of the early AthlonXP Thoroughbred CPUs which have their multiplier unlocked, as that provides even more slowdown range.

It should also be noted that there are speed sensitive Win9x games as well. Star Wars: Shadows of the Empire is one example.

Joseph_Joestar wrote on 2021-10-22, 07:08:

RandomStranger wrote on 2021-10-22, 06:38:

The Athlon XP can cover the Win9x/XP switch, but I don't know how much it can be slowed down.

Pretty well using ACPI Throttle on a VIA chipset. As mentioned before 386, 486 and early Pentium speeds are all achievable on that platform. For best results, you want one of the early AthlonXP Thoroughbred CPUs which have their multiplier unlocked, as that provides even more slowdown range.

It should also be noted that there are speed sensitive Win9x games as well. Star Wars: Shadows of the Empire is one example.

Is that using throttle.exe? What exactly does apci throttle do?