adding a 3.5" floppy drive

[dphirschler]

My PE Box has dual floppy drives (probably DSDD, and maybe even 1.2MB - I have to check). I want to swap out one of the 5.25" floppy drives with a 3.5" floppy drive. I know I had this setup when I was younger, but I can't remember the details. So I'd like some advice with it. Can I just swap out one of the 5.25" drives with the 3.5"? Should I use A or B for the 3.5" and why? Anything else I need to worry about?

 

 

Darryl

[+arcadeshopper]

My PE Box has dual floppy drives (probably DSDD, and maybe even 1.2MB - I have to check). I want to swap out one of the 5.25" floppy drives with a 3.5" floppy drive. I know I had this setup when I was younger, but I can't remember the details. So I'd like some advice with it. Can I just swap out one of the 5.25" drives with the 3.5"? Should I use A or B for the 3.5" and why? Anything else I need to worry about?

 

 

Darryl

Depending on the controller you have you can either use them as 360k or 720k ONLY on a 4/a.. A geneve can do 1.44mb with a Myarc hfdc only.

 

A 720k disk drive will work fine out of the box, with 720k disks.. A 1.44mb drive will work if you use 720k disks or cover the HD hole on a 1.44mb diskette you can format it as DS/SD on a TI controller or DS/DD on a myarc or corcomp..

 

I have found that most 1.44 drives are hard wired to be DSK2. I have one plugged into my Corcomp controller as DSK2. by just plugging it in with a straight through cable. Imho it's best to never use twists in disk cables on a TI.

 

A great website on this is: http://www.mainbyte.com/ti99/2drives/2drives.html

 

Greg

[+OLD CS1]

Just beware of using HD floppies in a DD drive. Yeah, there are still some real DD drives out there, though expensive. HD floppies have a higher coercivity than DD floppies, and thus the drives use a weaker magnetic head than HD drives. While a DD drive can write to an HD floppy, it will not be as reliable and will suffer bit-rot more quickly as the magnetic domains are not "set" as well as they should be.

[dphirschler]

What do the twists do? I haven't taken my PEB apart yet to see the cables in there. But I do have a Myarc controller, so I think it can handle the DSDD (does it do HD?). Could my 5.25 drives be 1.2MB HD drives?

 

Darryl

[+Lee Stewart]

What do the twists do? I haven't taken my PEB apart yet to see the cables in there. But I do have a Myarc controller, so I think it can handle the DSDD (does it do HD?). Could my 5.25 drives be 1.2MB HD drives?

 

Darryl

 

You won't find any twists on cables coming from a TI diskette controller. Those were for IBM PCs and clones.

 

Originally, there was only one motor line that powered all floppy motors on the same ribbon cable and 4 drive select lines (one for each of drive 0, 1, 2 and 3). I read somewhere that IBM didn't think its PC had enough power to drive all four motors at once, in the event a PC had more than one drive. So, they required that all drives be set at drive select 1 and use only 2 drives per cable. The original controller had 2 cable connections, one for drives 0 and 1 and another for drives 2 and 3. The ribbon cable was supplied with the twist for drive 0 to put the drive 0 select line on the drive 1 select pin and the drive 0 motor select line on the motor select pin. The same goes for the second set of drives with the same cable twist, but now plugged into the second controller port for drives 2 and 3 (still each jumpered as drive 1).

 

This setup, of course, wreaks havoc with the TI-99/4A's diskette controller, which makes use of the individual drive select lines (at least for drives 0, 1 and 2 for the TI controller) and, I believe, uses only the one motor control line. Later 3.5" drives were hard-wired as drive 1 so would have to be used only as drive 1 or hacked to change it for the use of more than two 3.5" drives. Of course, one might find older drives with the drive-select jumpers.

 

...lee

[Asmusr]

I'm having some problems with two 3.5" drives I bought on EBay. Both drives work fine as DSK2, but none of them work as DSK1. I get a device error 6 from DSK1 with almost everything I try. The only thing I can do with DSK1 is to (apparently) format a disk, but when it gets on to verify the disk it fails in every sector. I thought it might be the cable, so I got a new one, but it has exactly the same problem. I have a standard TI disk controller card. Any advice?

Thanks,

Rasmus

[marc.hull]

I'm having some problems with two 3.5" drives I bought on EBay. Both drives work fine as DSK2, but none of them work as DSK1. I get a device error 6 from DSK1 with almost everything I try. The only thing I can do with DSK1 is to (apparently) format a disk, but when it gets on to verify the disk it fails in every sector. I thought it might be the cable, so I got a new one, but it has exactly the same problem. I have a standard TI disk controller card. Any advice?

Thanks,

Rasmus

Do the drives have jumper selects for drive number? I assume so since your swapping cables with no mention of mods on the cable?

[+arcadeshopper]

 

I'm having some problems with two 3.5" drives I bought on EBay. Both drives work fine as DSK2, but none of them work as DSK1. I get a device error 6 from DSK1 with almost everything I try. The only thing I can do with DSK1 is to (apparently) format a disk, but when it gets on to verify the disk it fails in every sector. I thought it might be the cable, so I got a new one, but it has exactly the same problem. I have a standard TI disk controller card. Any advice?

Thanks,

Rasmus

 

 

All 1.44 drives are set up as dsk2 from the factory. You have to either solder remove the jumper off dsk2 and add it to dsk1 (or if your lucky just move the jumper but most of these are not jumpered but soldered) cables that are for the TI have no twists.. need to be straight through.. and the drive select needs to be on the drives themselves twists don't work

 

Greg

[Gazoo]

 

All 1.44 drives are set up as dsk2 from the factory. You have to either solder remove the jumper off dsk2 and add it to dsk1 (or if your lucky just move the jumper but most of these are not jumpered but soldered) cables that are for the TI have no twists.. need to be straight through.. and the drive select needs to be on the drives themselves twists don't work

 

Greg

 

Actually, some twists work perfectly fine with any TI compatible controller. It's the IBM standard twist cable that doesn't work with the TI.

 

A twist involving wires 10, 11, & 12 would swap drive select lines 1 & 2.

A twist involving wires 10, 11, 12, 13, & 14 would swap drive select lines 1 & 3.

A twist involving wires 12, 13, & 14 would swap drive select lines 2 & 3.

A twist involving wires 6, 7, 8, 9, & 10 would swap drive select lines 1 & 4.

 

Any other drive select swaps would involve cross splicing the cable select lines, which is also not very difficult to do.

 

The chart below, taken from the HFDC manual, provides the info needed to create the proper twist in the cable.

 

Gazoo

Edited August 14, 2014 by Gazoo

[+arcadeshopper]

 

Actually, some twists work perfectly fine with any TI compatible controller. It's the IBM standard twist cable that doesn't work with the TI.

 

A twist involving wires 10, 11, & 12 would swap drive select lines 1 & 2.

A twist involving wires 10, 11, 12, 13, & 14 would swap drive select lines 1 & 3.

A twist involving wires 12, 13, & 14 would swap drive select lines 2 & 3.

 

Getting drive 4 involved requires splicing the cable, as it would interfere with other signals as it's select line is pin 6.

The chart below, taken from the HFDC manual, provides the info needed to create the proper twist in the cable.

 

Gazoo

 

 

So yes, PC twisted cables don't work with the TI.. either roll your own or use the drive select on straight through..

 

Greg

[Asmusr]

Thanks. I should have mentioned that my cable has a twist, but it's from a kit specifically made for the TI, so it's supposed to work. Perhaps I got a standard PC cable in the kit by mistake? The new cable I bought is just a standard cable.