Well, I have had a similar problem yet with a Pentium III- class machine: I could not have 2 devices (e.g. a CD-ROM and an HDD, or 2 HDDs) on a single physical ribbon cable. I tend to blame the SATA-IDE and LGH-IDE converter cards. Are you using native IDE devices, or modern ones with converters? Can you have a single device (presumably HDD) working separately?

Hello and thank you for replying,

In my case, I can indeed connect two devices to the IDE port with the result I described; the outcome is the same even when connected individually. All the hardware and cables I’m using are old, with no adapters.

Best regards!

Hello,

That looks like a UM8672 IDE chip. It has a speed setting from 1 to 18 set via um8672.sys in config.sys. In addition, its initial speed setting is set via jumpers.

If the speed setting is too high, it will misbehave exactly like this. Per the jumper doc on https://theretroweb.com/expansioncards/s/dfi-mio-2080#docs JP3/JP4/JP5 and JP8/JP9/JP10 all need to be set to 1-2 for the slowest setting. Either your card is already set on the slowest, or is set to the fastest; it depends on which side is pin 1 and I can't tell. If you are set to the slowest already, then aside from cleaning the edge connectors I don't have any suggestions. The UM8672 does work for me so long as it isn't set too fast.

Thank you very much for your reply!

I’ve been changing the jumpers, but it hasn’t improved… I’m pretty sure it has to do with them because I believe the board itself is fine.

It’s possible the manual doesn’t fully match the board… it at least confuses jumpers 1 and 6.

I tried with another ISA controller card and everything works perfectly.

Unless someone has the same board and can show me the correct configuration, I’ll probably have to get rid of it…

Thanks again!

How fast is the CPU, if it's a 40 or 50MHz, you may need to look for a BIOS or motherboard setting to waitstate the VLB

Hello!

It's a 486 DX 33 Mhz. (The motherboard can work up to DX/2 66 Mhz)

Thanks!

You could try making a DOS boot floppy disk on another machine, put the UM8672.SYS driver on it, (along with your CD-ROM driver and MSCDEX) and try putting it in config.sys on the boot disk with a conservative speed setting.

If, booting from that disk, C: and D: now work correctly, you know it's a speed issue.

Sounds like the signals are not getting through reliably.

Could be a speed issue like JakeThompson described. Could be a bad electrical connection. First make sure you don't have power cabled wrapped around the IDE cable. I always have to ask that. Then I would try replacing the IDE cable, cleaning the IDE pins and the edge connectors on the card, and then try inserting and removing the card a couple times in the slot to scrape away dirt or corrosion.

After that, maybe replace capcitor C7. Looks like it took a hit.

And then? It could be that the IDE controller is dying. I don't have a lot of statistical evidence, but in my experience the UM8672 chips seem to have a shorter half life than other cards of that era.

jakethompson1 wrote on 2025-07-29, 16:22:

You could try making a DOS boot floppy disk on another machine, put the UM8672.SYS driver on it, (along with your CD-ROM driver and MSCDEX) and try putting it in config.sys on the boot disk with a conservative speed setting.

If, booting from that disk, C: and D: now work correctly, you know it's a speed issue.

Thank you all very much for your answers!

I'll try the solutions you gave me and see if any of them work.

By the way, what would be the correct syntax for UM8672.SYS in the CONFIG.SYS file?

Thanks a lot!

https://vogonsdrivers.com/getfile.php?fileid=1999

README says:

1Add following statement to your CONFIG.SYS file to auto load the driver during bootup.
2
3device=[drive:][\path\]UM8672.SYS[/D<n:m>][/Cyl<n:m>][/Hd<n:m>][/Sec<n:m>]
4
5where:
6		  D<n:m> Drive n speed m(0-11) ( 0 the lowest )
7		  Cyl<n:m>  Drive n(2-3) cylinder number m
8		  Hd<n:m>  Drive n(2-3) head number m
9		  Sec<n:m>  Drive n(2-3) sector number m
10
11
12	     For instance, the user wants to load UM8672.SYS with drive 0
13	     speed = 6, and the DOS driver resides in the root directory of
14	     the drive C:. Add the following statement to your CONFIG.SYS file.
15
16		DEVICE = C:\UM8672.SYS /D0:6
17
18	     You don't need to specify drive speed and Cylinder, Head, Sector
19	     parameters usually, because the device driver is reconfigured for
20	     the optimal speed setting and detect the Cylinder, Head, Sector
21	     automatically.
22
23	III. Reboot your system.
24
25	IV.  UM82C863, UM8663, UM8668 & UM8672 Software Switch Function
26	     En/Disable Hot-key (F10):
27
28	     You can press F10 to get such a picture (power on default):
29
30	1. FDC En/Disable                             : Enable
31	FDC Port Select                               : 3F1 => 3F7
32	2. Primary Serial Port			              : Enable
33	Primary Serial Port Select		              : COM1 (3F8)
34	3. Secondary Serial Port			          : Enable
35	Secondary Serial Port Select	              : COM2 (2F8)
36	4. Parallel Port                              : Enable
37	Parallel Port Select                          : 3F8 => 37F
38	5. Primary IDE En/Disable                     : Enable
39	Secondary IDE En/Disable                      : Disable
40	6. Game Port En/Disable                       : Enable
41	7. Partition table write protected En/Disable : Disable
42
43
44	    Press <Escape>	 Key to Quit setup
45	    	    <Enter>	 Key to Set status & Quit
46	    	    <Arrow Up>	 Key to Select item up
47	    	    <Arrow Down> Key to Select item down 
48	    	    <Space>	 Key to Toggle status
49
50	     The user should consider the system environment to change
51	     the setup.

Thanks a lot!