View Full Version : Adding second drive.

October 9th, 2006, 05:44 AM
I want to add another FDD to XT.
Do I need to do something with termination blocks?
Or set settings on FDDs?

October 9th, 2006, 06:52 AM

There is plenty of information available online about this topic, including in "Upgrading and Repairing PCs" by Scott M. I've posted a link to the PDF for the 8th revision many times before.

Did you try searching and not find anything?

http://www.quepublishing.com/content/downloads/upgrading/fourteenth_edition/DVD/PCs8th.pdf#search=%22upgrading%20and%20repairing%2 0pcs%208th%22

October 9th, 2006, 11:02 AM
Yes, like he says "Use the Force, Luke!" :rolleyes:

October 9th, 2006, 12:42 PM
So if I understod good, I should remove T-RES chip from B: drive (in the middle of cable) and set drives to 'drive select'?

October 9th, 2006, 12:55 PM
On a bus that requires termination, the end device has to provide the termination. So whatever drive is at the end of the cable needs the terminator.

Drive select determines which drive is A and which is B. There are a lot of variations on how to do it.

Once again, all of this is well documented in many places.

October 20th, 2006, 04:14 AM
I couldn't find good solution to my problem.

So what should I do?
There are 2 FDDs.

I need to set mainboard's DIPs, remove terminator from B: drive.
But how should I set drives numbers? Wich should be D1 and wich D2, or maybe one should be D0...?

And what HS, HM and MX jumpers do?

Terry Yager
October 20th, 2006, 05:58 AM
Both drives should be set to the second device select, if the data cable has a twist in it. How to do it depends on what kind of drive it is.


October 20th, 2006, 06:51 AM
Both are DD 5,25" drives in Xt machine with non-twisted cable.

Terry Yager
October 20th, 2006, 09:41 AM
Device selection varies from one manufacturer to another. Sometimes it's a jumper block, sometimes a trace must be cut, etc. You really should find the documentation for your drive to see which method they use.


October 20th, 2006, 11:00 AM
Sorry... cable is twisted.
One FDD is full-heinght Tandon like those in IBM PCs and scond is half-height made by IBM.
I have jumper settings for Tandon drive, but I don't know how to set them.

Terry Yager
October 20th, 2006, 01:15 PM
Sorry... cable is twisted.
One FDD is full-heinght Tandon like those in IBM PCs and scond is half-height made by IBM.
I have jumper settings for Tandon drive, but I don't know how to set them.

If the Tandon drive came out of a genuine PC, it should already be set for the 2nd DS. If not, then you'll have to locate the DS jumper block, near the connector. It's a funny-looking DIP thinggy with like 6 or so little metal strips going across it. You select the drive by cutting one or more of the strips, but I don't recall exactly which ones. That info should be available somewhere.

The half-high drive should have a header block, also near the cable, and they are usually pretty clearly marked. just remember that both drives must be set to the second DS with the twisted cable, and the termination resistor goes on the last drive on the cable.


October 20th, 2006, 04:42 PM
Re HS, HM and MX jumpers. Whatever you do, don't change jumpers unless you know what they do. I don't know what they do.

You've got the required twisted cable, so as Terry said, set both drives to the second device select. For drives where that is done with jumpers, look for jumpers such as "D0", "D1", D2", "DS0", "DS1", DS2", etc. select the second one, e.g.
D0/D1/D2/D3 --> D1
D1/D2/D3/D4 --> D2

As for the full height Tandon, all I can do is show you a picture of my Tandon TM100.

October 20th, 2006, 11:07 PM
Thanks for help.
All I have to do now is to get or make a power splitter...

Tandon was set like that at your photo modem, so I need to set it on position 4.
Btw. here are settings for Tandon drive:


But could you guide me to somewhere where it's explained good?
When D0 is used? In my both Amstrad PC computers D0 is used in single-drvie system and double-drive one...

Terry Yager
October 21st, 2006, 10:55 AM
DS1 is the second device select, leave the jumper where it is.

Some manufacturers number thier drives 0, 1, 2, & (sometimes) 3, while others use 1, 2, 3, & 4. How the device is selected also varies from one make to another. IBM & most clones chose to set all drives as the second device, and re-arrange (twist) the cable to line it up with the correct pins on one of the drives. Before IBM-PC, I don't think anyone else used this method. I'm looking at a Texas Peripheral drive right now, and all four DS lines are connected, with no jumper block present. The intention was that the user/installer would cut the three unwanted traces on thr PCB, leaving only one device selected. However, when Tandy used these drives in the TRS-80s (the one I have was pulled from a Model III), they chose instead to use the data cable to select the drive, by not populating the connector with the unnecessary pins. Other makers used still different methods. Your Amstrad, f'rinstance, uses DS0 & DS1, as the drive maker intended, if I understand you correctly. Note that there will not be a twist in that cable.