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Two Questions about AST IO Plus II and Tandon Drive Select

Tincanalley

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Aug 26, 2019
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176
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Los Angeles, CA
Okay, so the AST board I have seems to have had the second serial port chip installed, but I can't figure out if this thing has the parallel port installed. I see so many empty sockets, but the only ones I can figure out are the ones that enable Apple Joysticks. I am attaching a pic of the board and hopefully someone can let me know if there is a parallel port or if I need to install the proper ICs (and which ones those might be).

For the Tandon, I am attaching two pics. If I'm not mistaking, all drives in an IBM 5150 should have the drive select set to DS1? If so, the A: drive is set that way, but the B: isn't. Also, I noticed that they messed up the pin insertion for pin 1, but since that isn't used, it shouldn't matter. Will the lack of cut shunts cause any issues? I haven't noticed any, though.

Thanks
 

Attachments

  • AST IO Plus.jpg
    AST IO Plus.jpg
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  • Drive A.jpg
    Drive A.jpg
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  • Drive B.jpg
    Drive B.jpg
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Okay, so the AST board I have seems to have had the second serial port chip installed, but I can't figure out if this thing has the parallel port installed. I see so many empty sockets, but the only ones I can figure out are the ones that enable Apple Joysticks. I am attaching a pic of the board and hopefully someone can let me know if there is a parallel port or if I need to install the proper ICs (and which ones those might be).
The manual for the AST IO Plus II is at [here]. The text in that is not helpful in regard to your question. Pretty much, if your card doesn't already have the "parallel printer (P) option" fitted, then "Order Part number IO-000P for parallel printer upgrade kit which consists of all the necessary ICs, printer adapter cable, and documentation."

The manual does though have a circuit diagram at the back. One page of that, labelled as 'PRINTR', is the printer port circuitry. The scan is poor, but I make out the following chips. If my reading is correct, then three chips are required:

U5: 74LS05 (already on the card)
U6: 74LS04 (already on the card)
U14: 74LS244 (empty socket)
U15: 74LS374 (empty socket)
U16: 74LS174 (already on the card)
U17: 74LS240 (empty socket)
U25??: 74LS125 (appears to be "U25" - if so, U25 is already on the card)
 
For the Tandon, I am attaching two pics. If I'm not mistaking, all {INSERT BY MODEM7: "floppy"} drives in an IBM 5150 should have the drive select set to DS1?
In some cases, yes, in other cases, no. Refer to the red text in the bottom-right corner of the diagram at [here].
In the specific case of the Tandon Tandon TM100-2, the answer is yes, because on that drive, Tandon designate the drive-select numbering starting at 0.

Also, I noticed that they messed up the pin insertion for pin 1,
I think the pin 1 thing was done on purpose. It seems unlikely to me that someone inserting the shunt block would not have noticed pin 1 sticking out like that after the insertion.

If so, the A: drive is set that way, but the B: isn't. Also, I noticed that they messed up the pin insertion for pin 1, but since that isn't used, it shouldn't matter.
Will the lack of cut shunts cause any issues? I haven't noticed any, though.
So, jumpered is 'DSO', 'DS1', 'DS2', 'DS3', 'MX', and 'SPARE'.

Based on what I read in the Tandon OEM manual (some below), the subject drive, jumpered that way, is always going to be 'selected'. So, as an example, if the other drive is selected by the controller for a 'seek to track 5' operation, the subject drive is also going to 'seek to track 5'.
As for signals coming back from the drives, I can see at least one problem. If the controller selects the other drive, and examines the state of the 'TRACK 0' line on the cable, if it sees that line asserted, that line could be being asserted by the subject drive, not the other drive (the targeted drive).

If the subject drive was mine, I would be adjusting the shunt block so that only 'DS1' is jumpered.

1648681598928.png
 
The manual for the AST IO Plus II is at [here]. The text in that is not helpful in regard to your question. Pretty much, if your card doesn't already have the "parallel printer (P) option" fitted, then "Order Part number IO-000P for parallel printer upgrade kit which consists of all the necessary ICs, printer adapter cable, and documentation."

The manual does though have a circuit diagram at the back. One page of that, labelled as 'PRINTR', is the printer port circuitry. The scan is poor, but I make out the following chips. If my reading is correct, then three chips are required:

U5: 74LS05 (already on the card)
U6: 74LS04 (already on the card)
U14: 74LS244 (empty socket)
U15: 74LS374 (empty socket)
U16: 74LS174 (already on the card)
U17: 74LS240 (empty socket)
U25??: 74LS125 (appears to be "U25" - if so, U25 is already on the card)
Okay, so I'm thinking that if I populate U14, 15 and 17 I should be able to use the parallel port.
 
In some cases, yes, in other cases, no. Refer to the red text in the bottom-right corner of the diagram at [here].
In the specific case of the Tandon Tandon TM100-2, the answer is yes, because on that drive, Tandon designate the drive-select numbering starting at 0.


I think the pin 1 thing was done on purpose. It seems unlikely to me that someone inserting the shunt block would not have noticed pin 1 sticking out like that after the insertion.


So, jumpered is 'DSO', 'DS1', 'DS2', 'DS3', 'MX', and 'SPARE'.

Based on what I read in the Tandon OEM manual (some below), the subject drive, jumpered that way, is always going to be 'selected'. So, as an example, if the other drive is selected by the controller for a 'seek to track 5' operation, the subject drive is also going to 'seek to track 5'.
As for signals coming back from the drives, I can see at least one problem. If the controller selects the other drive, and examines the state of the 'TRACK 0' line on the cable, if it sees that line asserted, that line could be being asserted by the subject drive, not the other drive (the targeted drive).

If the subject drive was mine, I would be adjusting the shunt block so that only 'DS1' is jumpered.

View attachment 1239752
I can do that. I think I will jumper it like the other one and remove the shunt block. Would an 8 pin dip plug right in? I figure the socket has to be compatible with a switch bank designed to be soldered.
 
In some cases, yes, in other cases, no. Refer to the red text in the bottom-right corner of the diagram at [here].
In the specific case of the Tandon Tandon TM100-2, the answer is yes, because on that drive, Tandon designate the drive-select numbering starting at 0.


I think the pin 1 thing was done on purpose. It seems unlikely to me that someone inserting the shunt block would not have noticed pin 1 sticking out like that after the insertion.


So, jumpered is 'DSO', 'DS1', 'DS2', 'DS3', 'MX', and 'SPARE'.

Based on what I read in the Tandon OEM manual (some below), the subject drive, jumpered that way, is always going to be 'selected'. So, as an example, if the other drive is selected by the controller for a 'seek to track 5' operation, the subject drive is also going to 'seek to track 5'.
As for signals coming back from the drives, I can see at least one problem. If the controller selects the other drive, and examines the state of the 'TRACK 0' line on the cable, if it sees that line asserted, that line could be being asserted by the subject drive, not the other drive (the targeted drive).

If the subject drive was mine, I would be adjusting the shunt block so that only 'DS1' is jumpered.

View attachment 1239752
I know why the drive worked as configured. Some idiot, instead of breaking the shunt, they cut the legs off. I pulled the shunt insert and it had all but leg 1 and 3 cut on one side and 1 on other side is the one sticking out. So they went about it the wrong way since looking at it gave no indication any of the connections were severed.

I have 8 switch dips for the drives and extra to do all other drives.
 
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