NMS-8250 with gotek and real 3,5" diskdrive not working?

Paragon (1126)

02-04-2018, 14:11

Hey guys.

If I replace the disk drive in my NMS-8250 with a gotek (flashfloppy), it works perfectly.
The original drive also works fine.

If I connect both, then it is not working...

Is it possible to connect 2 disk drives in a stock 8250?
Or do I need some different ROM for dual drive support?

Thanks!

By Wild_Penguin

Hero (644)

02-04-2018, 14:18

Hi Argon,

what kind of cable are you using?

You need to jumper the other drive as B (and the other as A).

AFAIK there's no difference besides 8250 and 8255 (except that the latter has another drive installed from the factory).

By Argon

Paragon (1126)

02-04-2018, 14:34

OK, the problem must be the jumper then.
I will try again

By Wild_Penguin

Hero (644)

02-04-2018, 18:35

Depending on the drive, it might not have a jumper. If it is originally meant for PC, those might not have a jumper since PCs use cable to select the drive, although the pinout is compatible (sometimes PC drives have spots for jumpers, but they are not soldered on). These drives are hard-wired as "A:" -drive (EDIT:See my posts below to clear up some confusion; PC A: = Shugard DS1 = MSX drive B: !).

MSX floppy drives do not have a standard, but usually are very close to the PC pinout or Shugart pinout. Some links that might come in handy:

http://pinouts.ru/HD/InternalDisk_pinout.shtml
http://www.hermannseib.com/english/synths/ppg/wtfloppy.htm
http://msx.hansotten.com/do-it-yourself/msx-floppy-drives/

By Wild_Penguin

Hero (644)

02-04-2018, 18:20

Also see NMS8255 service manual (at the time of this reply available here). On the NMS8250/55 and probably 8280, both connectors (MV and MW) have exact same pinout. You could use a cable which has the drives "in series" without a twist from the same connector (make one yourself if you don't have one) or use the existing cables that come with the 8255 (both are "straight").

The difference on the PC from the Shugart seems to be that the PC uses Motor A (=10) and Motor B (=16) pins (and the twisted part of cable chooses this instead of jumpers). On Shugart pin 16 is always Motor Enable, and should always be so on PC drives (IIRC "A" drive comes "after the twist" on PC).

Bottom line: NMS82XX uses Shugart standard. This is a rarity on MSXes, but makes using a floppy quite easy!

By Wild_Penguin

Hero (644)

02-04-2018, 18:37

Contrary to what I've written on my previous post, I realized after reading the pinouts, I believe a PC floppy drive (without jumpers / configured as drive A: ) equals the second drive, i.e. drive B: on the Shugart standard (and also on the NMS82XX). The "twist" on a PC floppy cable will swap pins 10&16 and 12&14.

The jumper (which is missing on PC floppies) on the contrary will select which pin:

12=default=any PC drive=Shugart DS1/B:,
10
14
16

According to the SM all of those pins are connected on the MB/controller. But I have no idea if the ROM supports so many floppies - would be interesting to test though!

EDIT:It is possible I've made an error. If someone spots one, please correct me!

By marcoo

Expert (111)

02-04-2018, 19:08

I use a Gotek to with a 8250 the only thing is you have to look how your jumersetting is
the gotek on DS0 if you want it to be your A drive and the normal floppy on ds1
for B-drive if it is a original drive that came with your MSX the jumpers are under your drive,

succes.

By Argon

Paragon (1126)

03-04-2018, 14:43

I was mistaken before, the "original" drive in my 8250 is not original but a replacement PC floppy drive.
I think it also has jumpers, will check and try again soon.

Thanks all!