Kruton 9000 wrote on 2024-06-26, 16:14:

ux-3 wrote on 2024-06-26, 14:01:

I can throttle my P3 down to around 386-16. It can emulate early 90s in speed. But from there to 500 MHz is a vast gap it can't cover. I can pick 500 MHz, 750 and 1000. Or I pick like 386-16, 25, 33. That is all I found, without swapping in a P2.

This is weird. Are there really no jumpers on your motherboard that set the bus to 66 MHz? On many boards even frequencies 75, 83 and more are available. Or Pentium 3 doesn't work with lower FSB?

Bios! This P3 has a (locked) multiplier of 7.5, which will give a spread from 500@66MhZ up to 1000@133MHz. Sure I can pick values between, but that is hardly needed at P3 speeds. Either it is too slow at 1000MHz or too fast at 500. It is more interesting when you slow it down. I can roughly generate SpeedSys rating from 4-8 when I disable the cache. If I want anything else, I can swap the CPU. With P2 and P3 I can cover 166Mhz-1100MHz. Or I cover SpeedSys ratings from like 2-9. That doesn't make this an all around DOS talent.

Shponglefan wrote on 2024-06-26, 16:19:

My experience with my Cedar Mill P4 is I have throttled it down to 286-12 MHz speeds. It can generally cover mid-range 486 (with cache disabled) down to 286. There is more of a gap above that, although Pentium speeds are achievable with ODCM / ACPI throttling.

Yes, ironically a P3 offers great slowdown, but is too slow for it to be used sensibly. When you speed up the CPU to P4+, things get more flexible.

Shponglefan wrote on 2024-06-26, 16:19:

I think it depends on what we mean by options here.

Maybe you want to call it choices. With a more modern board, you don't need to chose what you want but what you turn off, say to free IRQs. It feels a bit like reversed thinking vs P3.

Kruton 9000 wrote on 2024-06-26, 16:43:

Another thing Socket 775.

Well, that you do get quiet easily. But what do you do with the AGP next to it?

Grzyb wrote on 2024-06-26, 15:50:

Wait a minute... […]
Show full quote

Wait a minute...

*No* P4 chipset supports DMA, right?
Some - but not all - P4 PCI-ISA bridges *do* support DMA, right?

What's the practical difference between DMA support in the chipset vs. in the PCI-ISA chip?
Which ISA cards work with the latter approach, and which don't work?

I'd be curious to know this as well.

The handful of ISA sound cards I've tested on the two P4 motherboards (DFI / IMB200) have generally worked. This includes Adlib, Yamaha Audician 32 (YMF 7xx), Orpheus / Orpheus II, MK8330, PicoGUS, GUS Extreme, and AWE64.

The only issues I have run into are the GUS Extreme sometimes would fail to initialize (on the DFI board). Don't know if that's a bridge chip issue, a card issue, or a speed issue.

I've also tried out old video cards including CGA, Hercules and EGA video cards:

Lets be real. The only real benefit is availability of P3 motherboards with ISA and maybe power consumption, if you're feeling generous. AGP 3.3v? I assume you would want to use it only for some Voodoo cards, but there are options to use them via AGP-to-PCI adapter. So that's also an availability thing.

Kruton 9000 wrote on 2024-06-26, 16:43:

It's cool. Honestly, I never seen even one P4 ISA motherboard in my country.

I had to order most of mine from China and the US.

I know, but generally good fans for socket 478 aren't available. They were bad in Socket 478 times and later fans were rarely compatible with it. The problem can be solved, but it's a problem. Another thing Socket 775.

That depends on the heatsink. The Socket 478 coolers I have use 60mm fans. I just use Noctua fans with them, and they're quiet and efficient.

Grzyb wrote on 2024-06-26, 15:50:

*No* P4 chipset supports DMA, right? Some - but not all - P4 PCI-ISA bridges *do* support DMA, right? […]
Show full quote

*No* P4 chipset supports DMA, right?
Some - but not all - P4 PCI-ISA bridges *do* support DMA, right?

What's the practical difference between DMA support in the chipset vs. in the PCI-ISA chip?
Which ISA cards work with the latter approach, and which don't work?

It depends on if PC/PCI aka SBlink signals are present, which go up to ICH5 southbridge. The PCI-ISA bridge chips depend on those signals to get ISA DMA support, when those signals are not present the ISA slots present will only have IO and IRQ capability, but not working DMA channels so basically no sound cards. There are a number of Winbond and ITE bridge based P4 boards with fully working ISA slots.

Tiido wrote on 2024-06-26, 17:38:

It depends on if PC/PCI aka SBlink signals are present, which go up to ICH5 southbridge. The PCI-ISA bridge chips depend on those signals to get ISA DMA support, when those signals are not present the ISA slots present will only have IO and IRQ capability, but not working DMA channels so basically no sound cards. There are a number of Winbond and ITE bridge based P4 boards with fully working ISA slots.

So it's binary: DMA either doesn't work at all, or works as well as on P3 boards, right?

ux-3 wrote on 2024-06-26, 16:44:

Maybe you want to call it choices. With a more modern board, you don't need to chose what you want but what you turn off, say to free IRQs. It feels a bit like reversed thinking vs P3.

I'm not clear on what you mean. Are you talking about reserving resources in the BIOS? That's usually just a PnP BIOS feature. It's not something unique to P4 or later boards.

Grzyb wrote on 2024-06-26, 15:50:

[...]

Wait a minute...

*No* P4 chipset supports DMA, right?

Yes they do. LPC DMA is available up to at least the ICH5 on Intel chipsets and iirc it's there on various non-Intel ones too. That's what the DMA-supporting bridges interface with.

Some - but not all - P4 PCI-ISA bridges *do* support DMA, right?

What's the practical difference between DMA support in the chipset vs. in the PCI-ISA chip?

None - you need both for working ISA DMA.

Shponglefan wrote on 2024-06-26, 18:07:

ux-3 wrote on 2024-06-26, 16:44:

Maybe you want to call it choices. With a more modern board, you don't need to chose what you want but what you turn off, say to free IRQs. It feels a bit like reversed thinking vs P3.

I'm not clear on what you mean. Are you talking about reserving resources in the BIOS? That's usually just a PnP BIOS feature. It's not something unique to P4 or later boards.

In order to get sound cards to work in DOS, you need the right IRQs. Many boards have so many features (made decisions), that you will have to turn some off. If your board has the option to reserve IRQs, that is nice. But if you want to set up a PCI sound card, it can get crowded if you leave all features on. With a P3, you consider if a USB2.0 adapter is worth getting, and which adapter might work. With S775, you consider if it is worth turning it off.

ux-3 wrote on 2024-06-26, 18:21:

In order to get sound cards to work in DOS, you need the right IRQs. Many boards have so many features (made decisions), that you will have to turn some off. If your board has the option to reserve IRQs, that is nice. But if you want to set up a PCI sound card, it can get crowded if you leave all features on. With a P3, you consider if a USB2.0 adapter is worth getting, and which adapter might work. With S775, you consider if it is worth turning it off.

Ah, now I understand. You're referring to integrated peripherals (e.g. I/O ports, etc.).

Yes, turning off integrated peripherals to free up hardware resources is a thing, but again not unique to P4/S775 systems. It's just good computer management.

I tend to do this even with older systems that use I/O controller cards and are configured with jumpers. I've had to do similar things with older video cards and freeing up IRQ resources to use with sound cards.

dionb wrote on 2024-06-26, 13:18:

As for throttling, the Via C3 Nehemiah is throttle king. See: Every Speed Reference Point on a Single CPU - VIA C3 Nehemiah Only downside is that its top performance might be too slow (comparable to a P3-500 or so). On a P4, you have Throttle and it does what it should do to slow the system down, but doesn't get the CPU as aggressively low as is possible on Nehemiah.

Via C3 chips do seem to hold the throttling crown.

Though my P4 system does comfortably get down to 286 speeds. With ODCM or ACPI throttling, I can run Police Quest II at speeds comparable to my 12 MHz 286.

I've been meaning to do some more testing at low speeds to see if I get it to speeds similar to my Tandy TL. That would be my ideal target.

XT/Turbo XT speeds might be a little too ambitious for a P4.

Well, if you are still indecicive, how about this argument:
https://www.ebay.de/itm/125973705104
And no, I am not the seller nor the buyer...

Think of it as 'the build to end all builds'!
... just one more board... 😀

ux-3 wrote on 2024-06-26, 20:17:

Well, if you are still indecicive, how about this argument:
https://www.ebay.de/itm/125973705104
And no, I am not the seller nor the buyer... 😀

People trying to sell things for crazy prices on Ebay is nothing new. 🤣

FWIW, I paid about 1/20th of that for each of the DFI motherboards I have (each of which included CPUs, RAM and heatsinks).

I'm going to revisit my ISA P4 build soon. I just picked up this cooler. I actually have the Bigger 120mm version, but want to actually use a smaller cooler, as I'm thinking of putting a Zalman VNF100 on my 5900XT.

The board I use is the Soyo SY-P4I845PEISA

I really want to try Scrapcomputings throttle blaster with it to see how it behaves with speed sensitive software. I kinda want to just run one system and I think the P4 will be a good candidate for that, especially if the throttle blaster does what its intended to do!

That was it in its last configuration.

Bancho wrote on 2024-06-26, 21:50:

I really want to try Scrapcomputings throttle blaster with it to see how it behaves with speed sensitive software. I kinda want to just run one system and I think the P4 will be a good candidate for that, especially if the throttle blaster does what its intended to do!

Would love to see the results of Throttle Blaster on your setup!

Socket 478 should be ideal given the need to run a wire to the STPCLK# pin. OTOH, I'm still wondering how easy it would be to do on an LGA775...

dionb wrote on 2024-06-26, 18:09:

Yes they do. LPC DMA is available up to at least the ICH5 on Intel chipsets and iirc it's there on various non-Intel ones too. That's what the DMA-supporting bridges interface with.

LPC DMA is another matter and goes up to Intel X99 chipset from what I remember. PCI bridges do not care about LDRQ signal of LPC bus but only PCGNT and PCREQ signals of PC/PCI aka SBlink, which only go up to ICH5. IRQs come of same SERIRQ signal in both LPC and PCI to ISA bridges.

Grzyb wrote on 2024-06-26, 17:49:

So it's binary: DMA either doesn't work at all, or works as well as on P3 boards, right?

In theory yes, but there can be timing related issues from particular implementations. For example with Winbond PCI to ISA bridge, DMA recording on YMF71x cards doesn't work and sometimes there are buffer underruns in playback while an SB16 worked fine in such a setting.

Shponglefan wrote on 2024-06-26, 22:40:

Bancho wrote on 2024-06-26, 21:50:

I really want to try Scrapcomputings throttle blaster with it to see how it behaves with speed sensitive software. I kinda want to just run one system and I think the P4 will be a good candidate for that, especially if the throttle blaster does what its intended to do!

Would love to see the results of Throttle Blaster on your setup!

Socket 478 should be ideal given the need to run a wire to the STPCLK# pin. OTOH, I'm still wondering how easy it would be to do on an LGA775...

I just got my kit together save the Pi Pico. Still need to pick that up, but I am looking forward to working with it.

V

If we see it the other way, the only real advantage with a P4 system for DOS I can find is FPS in Build games at high resolutions. My "DOS monster" is a Thoroughbred Athlon XP 2600+ on a KT133A board. The monitor is a 19" LCD doing 1280x1024@75Hz. While the FPS is great at 1280x1024, it doesn't hit the monitor's cap. It's not as buttery smooth as if you lower the resolution to 1152x864 or 1024x768. A faster P4 system would probably hit 75 FPS@1280x1024 too.

Other than that, in my opinion there's only the fun in seeing how far you can go, and the bragging rights thing.

As a sidenote, there's a bug with at least GF3 and GF4 cards, either of which would be a natural choice in a P4 DOS system, that produces a really annoying flicker in the bottom of the screen in Build games at 1280x1024. You might want something else if that's your target resolution. No idea if it applies to higher resolutions aswell.

kaputnik wrote on 2024-06-27, 09:29:

As a sidenote, there's a bug with at least GF3 and GF4 cards, either of which would be a natural choice in a P4 DOS system, that produces a really annoying flicker in the bottom of the screen in Build games at 1280x1024. You might want something else if that's your target resolution. No idea if it applies to higher resolutions aswell.

There is a fix for that. If you use the NOLFB utility, it will fix the flickering issue and boost frame rates: NOLFB - Disables LFB enabling DOS games to fallback to VESA 1.2 modes

When combined with FASTVID it yields the best performance at higher resolutions with Build games.

Shponglefan wrote on 2024-06-27, 12:32:

kaputnik wrote on 2024-06-27, 09:29:

As a sidenote, there's a bug with at least GF3 and GF4 cards, either of which would be a natural choice in a P4 DOS system, that produces a really annoying flicker in the bottom of the screen in Build games at 1280x1024. You might want something else if that's your target resolution. No idea if it applies to higher resolutions aswell.

There is a fix for that. If you use the NOLFB utility, it will fix the flickering issue and boost frame rates: NOLFB - Disables LFB enabling DOS games to fallback to VESA 1.2 modes

When combined with FASTVID it yields the best performance at higher resolutions with Build games.

Ah, nice, will have try it at some point. Thanks for the info 😀