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I have installed two gotek device instead of two old unworking floppy disk drives (in particular on an Olivetti PCS 86).

And the result is something like this: Olivetti PCS86 with Gotek

(The one on the right should the the A: and the left one the B: as the connector end is at the right.)

Once switching on it can not detect the presence of the new floppy units. Switched on

Unfortunately, I can't find any information about Gotek jumpers configuration for MS-DOS. In addition, the machine seems to support only double-sided 720Kb floppies.

The Gotek(s) should already have the correct firmware because the drives were named "SFRM72-TU100K USB Floppy Drive Emulator 720KB for Industrial Automation" on ebay (from where I brought): so, luckily I need to take care only of the jumpers configuration.

What is the right one for MS-DOS / 720KB ?

Jumpers config. Connector head up

Finally, two final constraints:

  1. I would like to have them both working as I never saw two gotek drives on the same machine before.
  2. I would like to have data written/saved on the emulated floppies on usb

Is it possible? Do I need to take care also of this factor for the jumpers configuration?

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    It looks like you might have the cable connected backwards. The coloured marking along one side of the cable usually marks which side is pin 1, but silk screening on the drive PCB indicates that side of the connector is pin 34. That assumes you have the cable connected the right way around on the PC end. If they're backwards on both ends then that's not the problem.
    – user722
    Mar 21, 2019 at 4:44
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    @raffzahn Guidance on providing a retro computer with modern storage media is definitely on-topic here - Questions on SD-IEC for a Commodore 64 would definitely be accepted as on-topic and are pretty much the same thing. Such a question should be considered a retro preservation question (i.e. how to preserve a computer you cannot use because you can't transfer files to it)
    – tofro
    Mar 21, 2019 at 12:23
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    @Raffzahn SD-IEC is a modern device for the C64 - Still it would be on-topic. CF- or SD-card storage for the Amiga are modern devices - still, they would be on-topic. You might want to explain what's so special about the GOTEK you consider it off-topic.
    – tofro
    Mar 22, 2019 at 9:39
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    @Raffzahn You can't possibly claim DD floppy drives (and their replacement) should not be considered retro, do you? They are more than 20 years out of production.
    – tofro
    Mar 22, 2019 at 10:32
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    @Raffzahn The Gotek is modern, but configuring it for a PCS 86 requires knowledge of how its floppy drive controller operates, and how it expects its drives to be jumpered. From the "on-topic" portion of the help center: "Retrocomputing involves the restoration, preservation, history and maintenance of computer and gaming systems of yesteryear. Questions are welcomed on how to use or preserve computing equipment that is no longer manufactured or supported by the manufacturer." Does the fact that the Gotek peripheral is still manufactured trump the fact that the PCS 86 is no longer supported?
    – Kaz
    Mar 22, 2019 at 12:35

3 Answers 3

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Firstly, a little bit of background information. The Gotek is designed to work with a wide number of computers, not just IBM-compatibles.

The original standard for floppy drives (designed by Shugart) allowed for up to four floppy drives to be connected to one controller. The controller would indicate which drive it wanted to communicate with by activating a Drive Select signal on one of four wires (typically labelled DS* or S*), then activate the Motor On signal to spin up the drive. When installing a floppy drive, you would be expected to set the jumpers correctly for the intended drive number, and several other parameters.

IBM-compatibles use the same floppy dries, but in a slightly non-standard way. It only supports two drives, and has separate motor control for each drive. (See this page for a description of the pinout for Shugart and IBM cables.)

What IBM cleverly did was get rid of the need to set jumpers on the drives by swapping some of the wires in the floppy drive cable instead. All drives for IBM-compatible systems are shipped from the factory jumpered as drive 1 (B:), but a twist in the cable swaps wires 10 to 16 (seven wires) around for one drive, which swaps the Drive Select and Motor Enable signals. The net result of this is that the drive you plug in after the twist will respond to DS0 signals (as drive A:) and the drive before the twist will respond to the DS1 signals (as drive B:).

Assuming you have an IBM-style floppy cable, with wires 10-16 twisted, you will want to set both drives to S1. You will also need to configure the Olivetti's BIOS to expect two 720k floppy drives connected.

The MO jumper is likely controlling how the Gotek responds to the Motor Enable signal. The JA, JB, JC, and J5 jumpers are probably Gotek-specific settings.

You will also need to make sure that the floppy drive cable is plugged in the right way around: the coloured stripe along the cable usually indicates the location of pin 1, but in the picture you've uploaded the stripe is next to pin 34 of the Gotek (as labelled on the PCB). A genuine floppy drive will spin constantly with it's LED lit when you fit the cable upside-down, and the computer will fail to communicate with it. I would expect similar behaviour from a Gotek.

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I'd suggest moving the jumper from S0 to S1 - IBM compatibles expect drives to respond as Unit 1, not Unit 0.

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Thanks for all the support! I resolved in the following way, hoping this could help someone else with the same doubts in the future.

Connectors enter image description here

Jumpers on Gotek enter image description here

Resuming: 2 HxC Gotek drives (SFRM72-TU100K) on a 16bit-based XT-clone (cpu NEC V30 at 8MHz with 640MB RAM), 720Kb each, detected as A: and B:, read/write enabled, working well on MS-DOS (all versions).

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  • Glad to know you got it sorted. You've got the data cables connected in the standard PC way. The fact that you required S0 on both drives is surprising, though.
    – Kaz
    Mar 24, 2019 at 9:35
  • @Kaz, me too... the Olivetti PCS86 seems to be a more "modern" machine respect the IBM PCS Model 30 from which it derives...
    – Francesco B
    Mar 24, 2019 at 20:22

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