Will “BBC drives” work on TRS 80 model I?

[Abmvk]

On eBay I found a set of two diskdrives in one case, 5,25” with a switch for 40/80 tracks. The ribbon seems to have a connector not suitable for the TRS-80 ExpanSion Interface, but inside it looks like a normal connector. So I figured I could remove the existing ribbon cable, and put one fitting the EI instead.

But the diskdrives are sold as “for BBC”. Wil they work for TRS-80 as well?

 

[John(Wales-UK)]

Hi

What are the make and model of the disk drives?

 

[Abmvk]

They were advertised on eBay as “Watford Electronics Dual Floppy Disk Drive BBC Micro Computer 5.25'' Track 40 80”

 

[daver2]

Watford Electronics just put standard disk drives into a case with a power supply.

What you need to do is to find the pinout of the BBC micro disk drive and compare that with the pinout of the equivalent for the TRS 80 Model 1.

I would suspect that they will be the same... But it is the first check.

There will be the odd thing that could trip you up. This would be the stepping time, number of heads etc.

For the pinouts - locate the technical manuals and/or schematics for the two relevant machines.

You definitely can't use (for example) Apple IIe disk drives, PET disk drives - or other vendors - where they used bespoke 'stripped down' disk drives that are not 'standard' products.

Dave

 

[Eudimorphodon]

Man, why is it so difficult to Google up a photo of the BBC Micro’s drive connector/pinout?

From what I can tell BBCs use standard Shugart interface drives with the regular 34 pin cable, so unless they’re jumpered strangely or otherwise modified they should work on a Model I. It does look like 80 track drives weren’t completely uncommon with the BBC; these *can* work with the Model I but you’ll have to generate a custom boot disk so 40 track drives would be preferable. Does the listing specify?

A Gotek drive emulator hacked with FlashFloppy is another alternative. You don’t really need a case, you can power one with a 5v phone charger and the plastic box they come in is reasonably rugged.

 

[daver2]

This website links to the schematic for the master: https://stardot.org.uk/forums/viewtopic.php?t=22660

Looks like a standard 34-pin interface.

I used to have a 40/80 dual disk drive - and it had a switch on it to change modes. I assume it double-stepped if set to 40 tracks? This is what the OP describes.

Dave

 

[Malc]

I used to have a 40/80 dual disk drive - and it had a switch on it to change modes. I assume it double-stepped if set to 40 tracks?

Yep, Some drives had 40/80 functionality built in and some didn't, There were certain 80 track drives that could be modified for 40/80 track using a resistor / wire and a switch, Some Mitsubishi drive was a favorite to mod as i recall.

 

[Eudimorphodon]

FWIW, it can sometimes be a little sketchy interchanging disks between those 80 track drives (in 40 track mode) and real 40 track drives. Of course this is going to be a non-issue if you only have one TRS-80. The 80 track mode (combined with a DOS able to use it, like NewDOS/80 or LDOS) is a welcome capacity boost, especially if you don't have a double-density board.

 

[mdog69]

FWIW, it can sometimes be a little sketchy interchanging disks between those 80 track drives (in 40 track mode) and real 40 track drives. Of course this is going to be a non-issue if you only have one TRS-80. The 80 track mode (combined with a DOS able to use it, like NewDOS/80 or LDOS) is a welcome capacity boost, especially if you don't have a double-density board.

General rule is that a 40 track disc in an 80 track drive should be treated as read only.
Write to a 40 track disc in an 80 track drive and the disc will only be readable in an 80 track drive in 40 track mode, it won't work in a 40 track drive until its reformatted in a 40 track drive.

All to do with the width of the heads - 80 track drive heads are narrower than 40 track heads and will "only mow half as much grass, right down the middle" when writing.

"40 track mode" means double stepping, either by software, or with a switched drive, by hardware.

 

[Abmvk]

Man, why is it so difficult to Google up a photo of the BBC Micro’s drive connector/pinout?

From what I can tell BBCs use standard Shugart interface drives with the regular 34 pin cable, so unless they’re jumpered strangely or otherwise modified they should work on a Model I. It does look like 80 track drives weren’t completely uncommon with the BBC; these *can* work with the Model I but you’ll have to generate a custom boot disk so 40 track drives would be preferable. Does the listing specify?

A Gotek drive emulator hacked with FlashFloppy is another alternative. You don’t really need a case, you can power one with a 5v phone charger and the plastic box they come in is reasonably rugged.

It is not google that is difficult. Being absolutely not hardware/technical, not native English speaker and having trouble with understanding lots of the technical texts. I do understand it can be frustrating to have someone ask questions that are dumb for most people, but believe me, I am VERY grateful for all the help. To me, talking to humans who come down to my level works much, much better than finding it all out myself, as that would stop me immediately. I don’t dare to experiment with electronics.

 

[Abmvk]

FWIW, it can sometimes be a little sketchy interchanging disks between those 80 track drives (in 40 track mode) and real 40 track drives. Of course this is going to be a non-issue if you only have one TRS-80. The 80 track mode (combined with a DOS able to use it, like NewDOS/80 or LDOS) is a welcome capacity boost, especially if you don't have a double-density board.

I only have one TRS-80, and I have found a local computer museum that sells boot disks for the TRS-80, so I think that will be OK.

Do you recommend NewDOS/80 or LDOS? I know I used NewDOS/80 forty years ago but I don’t think that is going to be much of a reason

 

[Eudimorphodon]

It is not google that is difficult. Being absolutely not hardware/technical, not native English speaker and having trouble with understanding lots of the technical texts. I do understand it can be frustrating to have someone ask questions that are dumb for most people, but believe me, I am VERY grateful for all the help.

Oh, man, I'm sorry if you took that grumbling about Google as criticism of you/your question. I was seriously wondering why it was so hard to find a picture of the BBC Micro disc controller's connector. (The connector on the computer end.) I genuinely couldn't find one easily. The TRS-80's pinout (and that it's a card edge connector) is all over the Internet...

If it's a 34 pin ribbon cable from the drive box but the computer end terminates in an IDC pin connector (like a modern PC floppy connector) or some kind of D-connector you may be able to adapt it to a TRS-80 just by clamping a 34 pin card edge connector onto it in front of the original connector and not even have to replace the cable.

Do you recommend NewDOS/80 or LDOS? I know I used NewDOS/80 forty years ago but I don’t think that is going to be much of a reason

I used both, and I think I somewhat prefer NewDOS/80. LDOS might arguably be somewhat more user-friendly and it has some sophisticated features like "filters", but features like the PDRIVE method of configuring disk formats on the fly gave NewDOS/80 a real "power-user" vibe I liked.

 

[tradde]

Oh, man, I'm sorry if you took that grumbling about Google as criticism of you/your question. I was seriously wondering why it was so hard to find a picture of the BBC Micro disc controller's connector. (The connector on the computer end.) I genuinely couldn't find one easily. The TRS-80's pinout (and that it's a card edge connector) is all over the Internet...

That's how I took your comment. Not asking him why he couldn't do a simple Google search, but why sometime you yourself can't get any good hits. Sometimes it's just you have to find the right key words. But normally I find there is just nothing to find.

 

[Abmvk]

Oh excuse me, must be me, I hate to bother people with my questions, because I feel rather stupid but I am glad you explained

 

[Chuck(G)]

Re: 40 track vs. 80 track. It was not uncommon back in the day for a vendor to refer to a single-sided 48 tpi disk as a 40 track; the double-sided one would then be 80 track.
I don't know if this applies to this particular drive, but I wouldn't be surprised if it did.

 

[Dustym]

I found these images on the interweb. I hope they're of some help. Would be very interested to hear how you get on as there are many WE disks kicking about. I think 40 track SDSS as the best bet!

 

[Abmvk]

As soon as the drives arrive, I will post updates