View Full Version : GOTEK SFRM72-TU100K 720K FDD Emulator & XT FDC

IBM Portable PC
January 15th, 2014, 12:56 AM
I have no trouble with this device on a Tandy 1000/A (with a no-twist cable and jumper S0) however on an XT controller it selects the drive (the green LED illuminates at POST and then at BOOT) but there is no drive (USB thumbdrive) activity and of course "Insert System Diskette and Strike any key when ready".

The Tandy 1000 uses a pre-XT FDD interface (with no twists, DS0 and READY on pin 34) what could I be missing with the XT? I have the GOTEK as S1 at the end of a cable with the standard twist.

I'm going to take a look at the XT FDC schematic................

1. According to page 1-173 of the XT Tech Ref manual, pin 34 is NOT USED
2. Page D-47 shows that the 765 FDC READY pin (35) is not connected or at least is connected to "+"

I'm using this card in a Tandy 1000A (IRQ 6 is dealt with) by the way.

January 15th, 2014, 08:43 AM
That's true about pin 34 and the XT--for that matter, even a PC AT FDC has the READY pin tied permanently high--there are no PC-compatible FDCs to the best o my knowledge that give a fig about READY from the disk drive.

Where can a schematic of your 1000/A be found?

January 15th, 2014, 09:17 AM
Just for kicks, try the no-twist cable and jumper S0 configuration to see how it responds.

IBM Portable PC
January 22nd, 2014, 11:06 PM
Just for kicks, try the no-twist cable and jumper S0 configuration to see how it responds.

No joy there......

IBM Portable PC
January 22nd, 2014, 11:09 PM
I connected the Gotek to a 386DX40 and it instantly booted from the 720K floppy image on the USB flash drive.

Setting again are:

The emulators are a steal for $30-$50

I'm trying a few other suggested emailed to me by a forum member........

IBM Portable PC
January 24th, 2014, 12:38 AM
Enough....... I have just tried a FDC based on a Motorola MCS3201 and my Tandy 1000 now boots from the Gotek.

The card had a BIOS, however it works without it.

I guess the MCS3201 is more flexible than a NEC765?