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Adding second drive.

Luke

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I want to add another FDD to XT.
Do I need to do something with termination blocks?
Or set settings on FDDs?
 

Luke

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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'?
 

mbbrutman

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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.
 

Luke

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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

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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.

--T
 

Luke

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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

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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.

--T
 
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modem7

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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.
 

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Luke

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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:

http://www.selectric.org/ibmpc/tandon.jpg

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

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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.

--T
 
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