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View Full Version : Disk on module (DOM) with another IDE devive on same cable



KenEG
September 18th, 2017, 09:50 AM
I have never been able to get a DOM to work on an IDE cable, so when I use one I can't have a second device. Has anyone gotten this to work? If so, please give precise instructions on what cable, adapter, etc. you used.

Stone
September 18th, 2017, 09:58 AM
You can use two of these:

http://www.vcfed.org/forum/attachment.php?attachmentid=40841&d=1505757458

But your DOM(s) must have a master/slave selector switch. Not all of them have this option.

glitch
September 18th, 2017, 10:57 AM
The cable in the picture appears to be a board-to-wire interface -- that's meant to be soldered to a PC board, not plugged into a DOM socket or other ribbon cable. What you want is a cable with something like this crimped on:

http://www.mouser.com/ProductDetail/3M-Electronic-Solutions-Division/4640-6300/?qs=sGAEpiMZZMs%252bGHln7q6pmzaFaX6eWkWmzH4ieebL0b M%3d

https://i.imgur.com/RQXOeLU.jpg

That particular one is a 3M 4640-6300, there are many manufacturers with similar parts.

Stone
September 18th, 2017, 11:11 AM
That solution is five to ten times as expensive. The one I posted does the job just fine and also requires no assembly.

glitch
September 18th, 2017, 11:26 AM
That solution is five to ten times as expensive. The one I posted does the job just fine and also requires no assembly.

It's an example of the kind of part that is correct for the application, I'm not saying pay $10 for QTY1 at Mouser.

KenEG
September 18th, 2017, 12:28 PM
Thanks for the answers. I think my problem is that my DOMs don't have master/slave switches. To be clear, DOMs don't support cable select?

Stone
September 18th, 2017, 01:40 PM
It's an example of the kind of part that is correct for the application, I'm not saying pay $10 for QTY1 at Mouser.I understand. But I'm sure you realize that a large percentage of this board is made up of extreme cheepskates. So I'm giving them (and everybody else as well) an easy way to try this system out. If they like it enough to upgrade it so be it. OTOH, if they find it to be just a passing FAD they'll never really use they haven't wasted much money OR any assembly time on it. :-)

Additionally, it's not as simple as $10 for 'QTY1 at Mouser'.

You need two to make one adapter.

Plus some ribbon cable to go between them.

And a crimping tool.

That's $25 to $40 to fabricate one, $50 - $80 for two.

TIP: if you're using two DOMs you'll need TWO cable adapters. :-)

You can buy two (already made) for under $10.

Stone
September 18th, 2017, 01:41 PM
Thanks for the answers. I think my problem is that my DOMs don't have master/slave switches. To be clear, DOMs don't support cable select?Hey, if they don't have a M/S switch you can be sure they don't have a CS switch, either. :-)

glitch
September 18th, 2017, 04:07 PM
See, I was assuming that, being cheap, they'd crimp the connector onto an existing IDE ribbon using the bench vise, like I do :) (well, used to, I have a small arbor press now)

KenEG
September 18th, 2017, 06:19 PM
Ok, where can I get DOMS with master/slave switch affordably.

glitch
September 18th, 2017, 06:26 PM
What capacities? I still have a few 64 MB, 128 MB and 8 GB DOMs available, pretty sure they all have master/slave switches.

KenEG
September 20th, 2017, 01:22 PM
OK, I have been trying to figure this out. The end of the IDE cable is straight through, so anything plugged into it should work the same as plugged into the motherboard/IDE adapter directly. When I try this, the DOM works slowly and erratically. I am thinking the DOM is especially sensitive to interference or crosstalk? If so, would using an 80 conductor UDMA cable help? Then the middle connector on the cable is the same, except pin 28, cable select, isn't connected. Devices that support cable select should become slave when they see this pin floating rather than grounded, so my 2x CD-ROM drive should work, unless the DOM's default is "single" Which I would doubt on a modern device.

Anyone here have any thoughts on this? Feel free to correct anything I have said. I might pout for a while, but I will get over it.

Stone
September 20th, 2017, 01:53 PM
OK, I have been trying to figure this out. The end of the IDE cable is straight through, so anything plugged into it should work the same as plugged into the motherboard/IDE adapter directly. When I try this, the DOM works slowly and erratically. I am thinking the DOM is especially sensitive to interference or crosstalk? If so, would using an 80 conductor UDMA cable help?...What are you waiting for? Let us know the result after you try it.

KenEG
September 20th, 2017, 03:37 PM
LOL. I am waiting for the two UDMA 80 conductor cables I ordered today to arrive. I will update when I get to try it. I don't see a reason it shouldn't work. The computer I am working on only has two drive bays and 3 ISA slots so I can't just throw in more interface cards. Reminds me why I always bought towers after my first two IBM compatible computers.


What are you waiting for? Let us know the result after you try it.

KenEG
September 21st, 2017, 02:15 PM
OK, I found an 80 wire IDE cable that I didn't know I had. I also have a couple of male/male gender changer cables. First problem. Cable has blank for keying, adapter doesn't. So I very carefully break off the key pin on one side of the adapter and install the DOM on it. Computer booted from DOM and seems to work great.

Set CD-ROM to cable select and connect it. Computer boots so I download driver and copy it to a floppy. Insert floppy and...drive not working. Disconnect CD-ROM and floppy works. Hmmmm. Set CD-ROM to SLAVE and connect it. Floppy works and driver installs. Reboot, insert CD, and it WORKS!

So the answer is that you can do this, but you probably need the 80 conductor IDE cable. At least the DOM I used seems to be hard wired for MASTER.