Well, I've used a lot of those slot1 machines at work for several years, no problem. Last time in May 2008 (had to retire it due to thin client implementation). Sturdy 'little' things. The machine itself would work well as a simple DOS/98 box.
(we had win2000)

BUT, for bios options, I sadly can't recall, as I never saw the need(nor would it be wise) to tinker with these office machines.
I assume the options would be pretty slim though 😵

OTOH, I still can't see much need for any either, as long as hdd works, the only(?) limit would be OC'ing.

- Beware though, potential PSU ATX connector issues if not using the accompanying Dell PSU - don't know when they dropped the non-standard cabling layout. (google...)

And you probably know of the custom riser card, where all the ISA and PCI slots are located ?

Anyways, if you would expand some more on what exactly you'd want to tweak ?

Dell and Gateway used Intel-built boards.

They are good boards but they most likely have that proprietary ATX power connector like bestemor said. Dell for certain. Sometimes they use an auxiliary power connection as well, one that I've not seen used with most enthusiast boards.

ATX Aux 6-pin (the one with the wires in-line)
http://www.pcguide.com/ref/power/sup/partsMotherboard-c.html

Very minimal BIOS options. But they are built to be stable.

Yeah, I don't want to be anywhere near a riser card and an empty-except-a-riser-slot motherboard. The casing is not as easy to find for these custom mobos.

Some features I'm looking for are things like :

1. A system which provides easy down-clocking, in steps.

2. Fan spin control.

3. More liberal with cpu and memory tweaking

4. Jumperless bus switching.

5. Having more ISA and PCI slots than I really want. 😁 Or at least, those which do NOT have the shared ISA/PCI slot.

6. Full sized motherboard.

I remember the Slot 1 systems being more Hybrid friendly - good DOS games support and modest windows 9x games performance. Something like a socket 7, but slot 1 gives better Win9x performance. (At least the PIII ones.)

And not to mention I like those fanless slot-1 heatsinks - silent operation. (Usually I ventilate my casing well with large silent fans.)

Edit:

Sigh...looking back at the list, it looks more like an enthusiast motherboard features. I remember reading somewhere about some branded systems - built with gaming in mind those days, with some tweakability options...and somewhere where people discussed about certain extra functions available...just can't pinpoint it...

Edit2: Yeah, now that you mention it.... Gateway and Micron comes to mind.. I think the magazines were Computer Shopper...can't remember but the monthly magazine (British) is like a telephone directory!

It's been a few years since I've messed with one of the Dell ATX boards, but just from what I remember of 'em:

-Not really any user-configurable clock options to speak of. I think you could adjust the multiplier with an unlocked PII, but the bus speeds were strictly autodetected and limited to either 66 or 100, unless you used something like SoftFSB from Windows, which, IIRC, opened up 75, 112, and 124 options, maybe a couple more.
-The BIOS options were pretty limited in general, though not more than any other Intel-made board.
-No fan speed control. Actually, I don't remember ever seeing that on any Slot1 board.
-The proprietary power connector. It's easy to convert to standard ATX if you have some soldering skill, though... there are three unpopulated rows below (or was it above?) the ATX connector, just desolder the ATX connector and shift it over by three places, and then remove the 6-pin AUX connector entirely.

Those OEM Intel-built boards were available at the stores too. For example, the Intel SE440BX Slot 1 mobo. There are a few revisions of that and the later ones can run Coppermine.

The retail versions usually give you a few more BIOS options but still lack many of the settings you'll find on a ASUS/Abit/etc board.

I have two Dell GX1 machines here awaiting Tualatin Celeron transplants and these are among the boards that use a unique power supply that you can't upgrade with a regular ATX supply without a lot of hacking. They also don't have AGP slots, only an ATi Rage Pro onboard 2X AGP. As was mentioned earlier, these boards also require a riser card for the PCI/ISA slots and there's also a somewhat elusive to find video RAM expansion board for these. The video will work fine without it, but it will work better with more memory just like any other video card and it's hit or miss whether a particular machine has it or not. I have two complete machines and one bought as a basket case and only the basket case machine had the expansion (the main reason I bought it). You never know until you open it. I'd pass on trying to build a system around these unless you have a Dell machine that they fit.

You also can't upgrade the BIOS on the GX1 machines beyond version A7 if you want to use the fastest PIII CPU's. Versions after A7 remove support for CPU's higher than around 600 or 700mhz, I think it is, specifically to stop people from upgrading them.

these are among the boards that use a unique power supply that you can't upgrade with a regular ATX supply without a lot of hacking.

For the boards that don't have the empty spaces for moving the ATX connector, or if you just don't feel like soldering, there's also the option of buying adapters for a dollar.

BTW, I think I still have a few of those video SODIMMs, I could go dig for 'em if you need another one.

Hmmm...I guess the stability vs features really hit hard, especially with Dell motherboards, and most likely other branded ones too. One of the reasons I didn't jump into buying them till now.

http://www.oldskool.org/guides/oldonnew/friendlyboxes wrote:

Dell Optiplex GXpro 200: An Oldskooler's Dream The cream of the crop, the Dell Optiplex GXpro 200 is a Pentium Pro running at 20 […]
Show full quote

Dell Optiplex GXpro 200: An Oldskooler's Dream
The cream of the crop, the Dell Optiplex GXpro 200 is a Pentium Pro running at 200MHz, is my current machine, and is probably the best machine I've come across for running old games in addition to being an extremely capable workstation. While not listed on their website any more, you may still be able to purchase it from Dell by asking a sales representative on the phone about their old stock.

Here's the rundown on why this is the best oldskool machine I've ever owned:

Can toggle between 200MHz and 8MHz on the fly by hitting CTRL-ALT-\ at any time
The sound card is built onto the motherboard, which, in addition to saving an ISA slot, is 100% Sound Blaster 16 compatible, the settings are perfectly set at 220, 5, 1, 5, and the PC speaker is rerouted to output through the sound card! While the obvious advantage is the control of the PC speaker volume, the real benefit is that PC speaker digitized or synthesized sound is much clearer, since it's being output to real speakers instead of a piezo tweeter.
There's a free external drive bay, perfect for dropping in a 5.25" drive
The video card is not on the motherboard (unlike the sound card, which is), so I'm free to choose whatever video card I like (currently using an ATI card with full VESA 2.0 in BIOS 😀
There are other reasons this machine is great that are not directly related to running old games:

The case comes off easily; just push in two buttons on either side of the case and it lifts right off
The drives slide right out on their own chassis
The power supply easily rocks out of the way so you can get at the motherboard
The ISA and PCI card slots are contained in their own removable cage; you can lift the cage right out of the machine, put your ISA and/or PCI cards in, and then lower the cage right back into the machine
And that's without using a single screw! That's right--no screws.

It is entirely possible that many (or all) new Dell machines are like this, but you might want to peruse their excellent technical website to get the exact specs of the machine you plan to buy. On the OptiPlex GX Pro tech notes, the reference to the key-combo-triggered slowdown toggle is slightly obscure, but it is listed.

Malik wrote:

Hmmm...I guess the stability vs features really hit hard, especially with Dell motherboards, and most likely other branded ones too. One of the reasons I didn't jump into buying them till now.

http://www.oldskool.org/guides/oldonnew/friendlyboxes wrote:

Dell Optiplex GXpro 200: An Oldskooler's Dream The cream of the crop, the Dell Optiplex GXpro 200 is a Pentium Pro running at 20 […]
Show full quote

Dell Optiplex GXpro 200: An Oldskooler's Dream
The cream of the crop, the Dell Optiplex GXpro 200 is a Pentium Pro running at 200MHz, is my current machine, and is probably the best machine I've come across for running old games in addition to being an extremely capable workstation. While not listed on their website any more, you may still be able to purchase it from Dell by asking a sales representative on the phone about their old stock.

Here's the rundown on why this is the best oldskool machine I've ever owned:

Can toggle between 200MHz and 8MHz on the fly by hitting CTRL-ALT-\ at any time
The sound card is built onto the motherboard, which, in addition to saving an ISA slot, is 100% Sound Blaster 16 compatible, the settings are perfectly set at 220, 5, 1, 5, and the PC speaker is rerouted to output through the sound card! While the obvious advantage is the control of the PC speaker volume, the real benefit is that PC speaker digitized or synthesized sound is much clearer, since it's being output to real speakers instead of a piezo tweeter.
There's a free external drive bay, perfect for dropping in a 5.25" drive
The video card is not on the motherboard (unlike the sound card, which is), so I'm free to choose whatever video card I like (currently using an ATI card with full VESA 2.0 in BIOS 😀
There are other reasons this machine is great that are not directly related to running old games:

The case comes off easily; just push in two buttons on either side of the case and it lifts right off
The drives slide right out on their own chassis
The power supply easily rocks out of the way so you can get at the motherboard
The ISA and PCI card slots are contained in their own removable cage; you can lift the cage right out of the machine, put your ISA and/or PCI cards in, and then lower the cage right back into the machine
And that's without using a single screw! That's right--no screws.

It is entirely possible that many (or all) new Dell machines are like this, but you might want to peruse their excellent technical website to get the exact specs of the machine you plan to buy. On the OptiPlex GX Pro tech notes, the reference to the key-combo-triggered slowdown toggle is slightly obscure, but it is listed.

That page is obviously quite old judging by the prices being quoted for 386/486 motherboards. It's extremely hard to get old motherboards for those prices on ebay anymore.

oem's like Dell were known for using proprietary ATX PSU's in those days but I can confirm there are some Compaq and Gateway P3's that will run with normal PSU's

I tend to avoid anything proprietary like the plague