Depends if the mx400 has a DVI-A, DVI-I or DVI-D connector.

DVI-A is analogue only

DVI-I carries analogue and digital (and will work to HDMI)

DVI-D carries digital only (and will work to HDMI)

https://en.wikipedia.org/wiki/Digital_Visual_ … ector_Types.svg

megatron-uk wrote on 2021-08-06, 10:44:

Depends if the mx400 has a DVI-A, DVI-I or DVI-D connector. […]
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Depends if the mx400 has a DVI-A, DVI-I or DVI-D connector.

DVI-A is analogue only

DVI-I carries analogue and digital (and will work to HDMI)

DVI-D carries digital only (and will work to HDMI)

https://en.wikipedia.org/wiki/Digital_Visual_ … ector_Types.svg

Is there any device that has a DVI-A only output though? What would be the point in using the DVI connector then? I think DVI-A only is only commercially implemented on adaptor cables.

What is more important is wether the graphics card's DVI chip works well with the HDMI chip and wether the card defaults to DVI as the primary display if there's no VGA monitor connected or if it needs to be instructed by the driver first.

Sorry I can't be more helpful, OP! I can only tell you that I have used some 440MX with a passive DVI-HDMI adaptor cable before and it worked. It may be different for your individual card/monitor though.
Welcome to the forum btw.😉

I'm fairly sure I read somewhere that DVI-D is logically the same as HDMI (or at least, early HDMI, less sure about later versions and the encryption options), in that it's 4 TDMS channels, so if the card uses the digital output pins (as Doornkaat suggests, it probably does) then it should work since the adapter can be a passive device.

Maybe the card doesn't support the refresh rates/resolutions options the monitor reports back to it, and the monitor doesn't support whatever the card defaults to? Do you know if the cable works with other video cards? Also might be worth trying a different monitors/TV. Usual first step trouble-shooting of swapping bits around trying to find what works and what doesn't to help find the actual cause.

snufkin wrote on 2021-08-06, 12:46:

I'm fairly sure I read somewhere that DVI-D is logically the same as HDMI (or at least, early HDMI, less sure about later versions and the encryption options)

Yes - early HDMI up to 1920x1080/1920x1200 resolutions (single-link DVI). For higher resolutions, the standards diverge - DVI went the path of dual-link, HDMI raised frequencies.

Yeah that’s the problem right now, this is my first build of old parts since old parts were current. My monitor (Dell 2007fpb) is coming in next week, I was just wanting to give this a post test after I built it.

Has it got two of them by any chance? Thinking they usually had one DVI and one VGA, but if they put 2 of them on it, one of them might only be analog and the other digital.

2007FP has VGA, DVI-D, Composite (RCA) and S-Video.

As to why DVI-HDMI not working between an old card and a modern monitor - there can be various compatibility issues, even for sub-FHD resolutions.