This is how I'm measuring the PCI CLK.

Have you tried any PCI controller that works officially on PCI 66?
Perhaps a Dawicontrol DC-150 (RAID SATA)?

PCI is a weird bus, data is not just send as logic levels, its reflections https://en.wikipedia.org/wiki/Reflected-wave_switching
Quoting Howard Johnson High Speed Digital Design: A Handbook of Black Magic:

1Source terminators
2The driving waveform is cut in half by the series-termination resistor before it begins propagating down the line.
3The driving signal propagates at half intensity to the end of the line.
4At the far end (an open circuit) the signal reflection coefficient is +1. The reflected signal is half intensity. The half-sized reflection plus the original incoming half-sized signal together bring the signal at the receiving end to a full level.
5The reflected signal (half sized) propagates back along the line toward the source where it damps out at the source termination.
6After the end reflection returns to its source, the drive current drops to zero where it remains until the next transition.

Howard Johnson on PCI in more detail http://www.sigcon.com/Pubs/news/3_3.htm

try different PCI slot, fill all PCI slots with cards, remove all cards

Disruptor wrote on 2023-05-01, 13:07:

Have you tried any PCI controller that works officially on PCI 66?
Perhaps a Dawicontrol DC-150 (RAID SATA)?

I also tried an Adaptec Ultra160 card, which I'd imagine is at least PCI 2.2 compliant, but it was worse off than the 2940U2W. I tried to install an Adaptec Ultra320 card, which is 64-bit, but the overhang of the extended PCI slot was in the way of motherboard components. Thus, the card would not install.

Rasz_pl, I had no idea PCI worked like this. It sounds rather convoluted, but it has been a widely used bus for so long I figure the scheme must have been for good reason.

I tried all sorts of PCI slots. I tried filling the vacant PCI slot with other types of cards to see if it helped, but it didn't. I need to at least have the video and SCSI card installed to test if it works, and there's only 3 PCI slots.

I asked another member here to test the same situation on his motherboard, and he ran into the same trouble as me. The issue is with the motherboard and they likely didn't test above 50 MHz FSB. It is a drawback to the LSD board, as the only other socket3 board which can do 66 MHz FSB reliably. The other board, being the Biostar UUD board. Without a solution to this 1/2*FSB issue for the PCI slot, the LSD board is forced to use onboard IDE for 60/66 MHz.

I have found the PCI divider to be unreliable even at 50MHz FSB on the LSD. My system is rock solid at 50MHz FSB 1:1 but if I try to apply the divider things start crashing.

maxtherabbit wrote on 2023-05-02, 02:07:

I have found the PCI divider to be unreliable even at 50MHz FSB on the LSD. My system is rock solid at 50MHz FSB 1:1 but if I try to apply the divider things start crashing.

3x50 or 4x50?

What model hard drive controller are you using?

I didn't test 1/2*50 MHz in any depth - just wanted to ensure it would boot to DOS.

3x, my CPU is not able to run at 200. My HDC is a Promise Ultra133 TX2

maxtherabbit wrote on 2023-05-02, 04:45:

3x, my CPU is not able to run at 200.

For those runs I've bought an Am486 DX4 SV8B 120 and have given it to mkarcher so that he can test it in x2 mode. It works fine in 60x2 and 66x2.

The newer AMD DX2-66 CPUs from the early 2000's should be able to do 2x66 without issue problem, at least mine is OK with these frequencies. These have 16 KB WB cache and support 2x/3x multipliers.

Is it possible to force your PCI IDE card to PIO mode and see what happens then? Because if these cards are both having problems, at 60MHz and at 30MHz, it makes me wonder if something is going wrong on the DMA side of things. Maybe memory timings could be worth looking at too?

On a side note, I accidentally discovered that onboard IDE on my HOT-433, which normally doesn't work at 60MHz PCI, does work at that speed if XT-IDE BIOS is installed.

There's no way to access the the PIO/DMA settings on the Promise Ultra100 TX2 card from what I can discern. I think its BIOS is auto-detect only. You can trick it into DMA2 mode if you use a 40-pin ribbon cable, or into DMA5 mode if using an 80-pin cable.