Floppy drive cascade, dangerous ?

[suppah]

Hello,

i know it may sound crazy but i love playing games from floppies, at least when the number of disks is not huge.

I've been buying floppy readers and wanted to put them in cascade, how is it safe ? I've found an old recommendation that cascading "too many" drives is a bad idea and can damage the Amiga.

As always, where is the truth ?

[alexh]

The maximum is 3 so how many is too many?

[suppah]

From what i read two is already dangerous. The paper mentioned the best would be to have just one external drive.

[thebajaguy]

Paula and the 8520's support 4x floppy disks (SEL0-SEL3). The PSUs support all internals, and up to one external. Any additional externals after the first unit must be powered externally. Length of the data cables should be kept shorter, and shielded.

[suppah]

I see, that makes sense, thanks

[solarmon]

Ultimately, it just depends on the power supply your Amiga has and what it can supply on the 5v (and for some drives,12v) line.

If your power supply can cope with it, then there is no reason why you can't connect three external drives.

Maybe, with the stock power supply that came with the Amiga, it is recommended to only power a single external floppy drive, but with modern replacements, this should not be an issue.

[TCD]

Originally Posted by solarmon

Maybe, with the stock power supply that came with the Amiga, it is recommended to only power a single external floppy drive, but with modern replacements, this should not be an issue.

I ran two external floppy drives back in the day with the original power supply on an Amiga 500 without any issues. Might just have been luck though.

[alexh]

Originally Posted by suppah

From what i read two is already dangerous. The paper mentioned the best would be to have just one external drive.

Originally Posted by thebajaguy

The PSUs support all internals, and up to one external. Any additional externals after the first unit must be powered externally.

I'm curious to know where you got this information from? And if it is accurate?

The dual drive from Power Computing had it's own power supply.

https://bigbookofamigahardware.com/b...ct.aspx?id=783

The KCS Dual HD Deluxe which has 1.44MB support and Cyclone support (so arguably more electronics) doesn't.

https://www.amibay.com/threads/kcs-dual-hd-drive.54240/

[pandy71]

Originally Posted by solarmon

If your power supply can cope with it, then there is no reason why you can't connect three external drives.

Maybe, with the stock power supply that came with the Amiga, it is recommended to only power a single external floppy drive, but with modern replacements, this should not be an issue.

Well, issue can be connector capability, PCB (traces) in Amiga capability etc,
newer floppy drives are usually way less power hungry than old ones - so i can imagine slim, notebook floppy drive will consume fraction of power when compared to normal, old style floppy - especially for USB floppy drives where 500mA 5V is absolute max. Such 2 floppies can be stacked and both active should consume still less power than original Amiga floppy drive.

[thebajaguy]

Where do I know the limit of one external?

I worked for GVP back in the day. We built and sold external floppy disk units. That was C= spec, and it was based a simple electrical reason.

The reason was due to the DC voltage drop over thin copper wire as the length of cable got further from the source.

Commodore provided a circuit on the original PSU/cable, where it is looping back to inside the PSU. It would 'check' for the voltage drop at the motherboard and compensate. There was no additional power adjustment available on daisy-chained external devices. The 12V drop off % far enough out would eventually affect the motor's spin speeds.

You could probably get away with additional Gotek-type devices, but I would still suggest checking the 5V level (and 12V if using mechanical drives) at the end of the chain. +/- 5% is all the tolerance that TTL devices support before you end up in a gray-area, and the potential for errors occur.

One warning about 'modern' PSU replacements for the A500/600/1200. Some 'popular' modern PSU replacement solutions don't mimic the C= PSUs drop compensation circuit, so be careful with your system loads and tuning the PSUs. You can over-voltage the system if you tune it manually for a heavier load (multiple internal and external expansions), and then remove that load.

[Jope]

You can also get away with multiples of most 3rd party 1" tall externals. They only use +5V. Naturally it does put a strain on your PSU, especially if it is the wimpy 2.5A model.

[simon_m74]

I used to have 3 external floppy drives on my Amiga 500, to help with Monkey Island 1 & 2
I had 3 on there for years.....
Now, I dont have all those drives, but my Amiga still works!

[Jope]

Three A1010s would probably cause a brownout though. :-)

I checked the A500 user's guide and it mentions that you can add one 3.5" and one 5.25" drive. No doubt because the A1020 has a built in PSU.

[solarmon]

The A1010's don't actually have the power rails passed through to the daisy-chain floppy port. You have to mod it.

[Jope]

I never noticed, makes sense. :-)