And a few more pics. This is when it would detect the HDD. I selected (2) as it offered that as the suggested default option

You really want to avoid 20 GB+ HDDs with a 486 😀 And as for 40 GB... this is usually too much even for many Socket 7 boards (although some of them do have BIOS patches that allow disk sizes up to 128 GB).
Do yourself a favor and get a 2 GB CF card and a CF to IDE adapter, and you should be good to go. In your case, it seems you have a late 486 board, which will probably handle fine even 8 GB disks. But to be on the safe side, keep it simple and go with 2 GB. Keep in mind that 2 GB would've been mind blowing on a 486 at the time 😀 20 GB... damn, that was already "alien technology" territory 😁
Another option would be to use Seatools (on a newer platform, of course) and limit your 20 GB HDDs size to 2 GB (and work your way up from there, see what works and what doesn't).
From my experience, even if the HDD is apparently detected, you can have all sorts of issues (like data corruption and other strange behavior), so it's best to stick to (almost) period correct sizes.

Weather or not this is related to the issues you're having with the floppy drive... hard to say. But I'd fix the HDD size problem first and take it from there.

Hi bloodem

Thanks for the reply. Seeing as I have the seagate 20Gb and I have other hardware that runs XP (or Win 7 for that matter) and has IDE as well as SaTA - could you elaborate a little on using Seatools to limit the 20Gb to 2Gb. Does it do that by changing the HDD BIOS or something? The instructions seem fairly simple to follow. Once that is done, when I reconnect the drive to the 486 does it automatically detect as 2Gb?

I may as well try that first as I have everything here that I need, if I have no joy I will get the IDE CF adapter and try that.

Cheers

For seatools you can watch this guide that Phil posted on youtube some years ago.
And yes, after using this tool, the HDD will basically report a different size (whatever you set it to). However, I should mention that I've had mixed results with this method and 486 motherboards. Some boards work great, others not so much and they still continue to have issues.

Aha! one of Phils videos - he's the best 😀

Hi
I formatted the 20Gb HDD (FAT 32). Then I made a bootable CD and tried the Seatools for DOS as per Phil's tutorial. And it appeared to work - see pic.

But the SIS 496 still will not detect the HDD either in the BIOS or when it boots. I am really puzzled now as yesterday it did detect it (for a while) as seen in my posted pics and the HDD is clearly working OK. I guess I can try the CF to IDE, they are not expensive but will take a while to arrive here by post, most likely a couple weeks. That's the worst problem of living in paradise 🤣

I hope you did not damage the onboard IDE controller 😀

Yeah me too -but I can't see how that would have happened as anything I plugged onto it was later tested on my Core 2 rig while I was working on the 20Gb NDD and it didn't damage that - though I can cofirm two of the IDE CDROMs are now in the trash as I couldn't boot my seatools CD with them.

You can cap the HD to 3.2GB as on the label.
If you want to upgrade to a bigger HD you can always make an image and restore it on the new HD.
You'll have your 486 running in the meanwhile. Yes, buy a CF to IDE adapter and a flash card.

My big issue when I finally opened up my box old old retro stuff and started playing around was that 2 of my 3 floppy drives didn't work properly, one of my old IDE controllers didn't do floppy drives any more, one usb floppy drive was quiet dead, and the usb floppy drive that seemed to work must be been out of alignment because it was the only drive that could read the disks it wrote. Multi-variable troubleshooting is no fun. Much cursing. Days of trial and error passed until I scored a trash bound Pentium 2 440bx system that had a working hard drive & floppy. I did a "sneakernet" to get bootable floppy images on that computer and then I was able to use that computer to make good boot floppies. Once I had a good boot disks, I was able to work out which drive was still good and which controllers were good.

Moral of the story: when working with computer hardware that is of legal drinking age, it's probably safer to assume that there are many broken parts, not just one broken part.

Generally these days I skip the boot disk all together unless I need drive overlay or mem test. Instead, I put the new drive in a working system, use free dos fdisk to make the partition and set it active, and then format d: /s. Of course moving hard drives between computers gets a lot more tricky if you need to use a custom drive geometry in the Bios to make the drive visible on one of the computers.

And Yes, get the CF adapter. If you get the kind with the female 40 pin connector, you may need to mod it if you want to do speeds faster that UDMA2.

Anyone have any good 3d printer models for a front mount CF holder?

OK so what I will try next is look on the HD label and see if actually I can cap it at 3.2GB as you say Nexxen, as I didn't notice that but then I didn't really look either. If Ican set it to 3.2Gb I can test it on one of my other motherboards. The 486 board does appear to support LBA in the BIOS so I honestly think it would work with anything under 8.5Gb

Also I'll try the HDD on IDE2 as I never thought to do that earlier. At least I know the IDE cable is good as I used it on the other rig with Seatools, and same for the HD itself of course.

There are no bent/broken pins etc on IDE1 but I will check for bad soldered joints on the 40 pin IDE connectors (in fact I may resolder them all) as it did seem to stop detecting the HDD some time between trying to find a working CDROM and trying different cables and HDDs.

A quick google for this chipset says the IDE ports are buffered from the 85C496

http://www.bitsavers.org/components/sis/85C496.pdf

So even if I damaged something it would more likely be the buffer IC's than the chipset. Depending on availability of parts (I can't see the number of those IC's on the pics I posted, but I'd guess they were the two behind the IDE ribbon cable, and the mobo is at my workshop so I can't check right now) it would be real easy to change the buffer chips. It would also be easy enough to change the 85C496 itself, other than I wouldn't know where to find a replacement part.

So I don't think it is dead just yet.

Rich

I had a look - those two ICs near the IDE connectors are 74F245PC - octal 3-state bidirectional bus trancievers - and they definitely buffer the 85C496 from the IDE connector. And they are easily available. I'll check IDE2 connector on Monday and also have a look around the 74F245 with my scope - that should soon tell me if they are actually functional or not. I'm also ordering the IDE CF adapter.

Rich

If you didn't order the IDE CF adapter yet, you may want to look at SD2IDE instead. I'm running them in a 486 /w DOS and a Athlon64 Win98 machine.

CF is pinout compatible with IDE which is great, but it's not really supported media anymore. SD cards seem to have more availability.

Just a little update
I've orderd a CF2IDE adapter and a 2Gb CF card. Actually I found the availability (and prices lower) than the SD2IDE. Just have to wait for it to arrive now.