Hmm.. was there ever an 8" floppy drive for the BBC?

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blackwitch
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Hmm.. was there ever an 8" floppy drive for the BBC?

Post by blackwitch » Sat Aug 31, 2019 9:12 am

Hi all.

Just wondered if there ever was an 8" floppy drive made for the BBC?

It seems probable I suppose so I just wondered.

Thanks

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Elminster
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 10:09 am

I guess you could get it to work with some effort.

Not sure why you would want them though. 5 1/4 had been out for sometime by the time the Beeb came out. 8 inches are huge, And not just in size but in weight. I have a dual 8 inch unit with for my SWTPC, not weighed it but it has got to be similar in weight to a 18 inch crt TV.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by blackwitch » Sat Aug 31, 2019 10:53 am

Hi.

Thanks... It's not that I want to get one working but did they make them back in the day?

Was there any 8" drives stamped with the owl logo, for example?

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Coeus » Sat Aug 31, 2019 11:30 am

I have never seen any. The diffences between the two shugart standards don't seem to be that dramatic and the 8271 dates from the 8" era so I suspect it may just be a case of making up the correct cable.

There is more info at: http://www.hermannseib.com/english/synt ... floppy.htm

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by BeebMaster » Sat Aug 31, 2019 11:50 am

The 8271 disc interface will support 8" drives, although as has been said, nobody seems ever to have used one. An additional modification to some links is required after fitting the 8271 upgrade - it's covered in 4.6 of the Service Manual.
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Sat Aug 31, 2019 12:15 pm

Splitting the question into two parts:
  • Was an 8 inch drive ever sold specifically for the BBC B Micro?
Very unlikely, most 5¼ inch drives were just standard 5¼ inch drives mounted in a generic case and appropriate stickers or screen printing added. These were rather expensive, so a bigger 8 inch drive would most likely have cost rather more. And by 1981, 8 inch drives were considered obsolete.
  • Did any one ever hook up an 8 inch drive to a BBC B Micro?
Well as details are given in the service manual, Acorn almost certainly did. It would not surprise me if various enterprising types also connected an old or surplus 8 inch drive to a BBC B Micro. Maybe just to try it. But as 8 inch drives were obsolete by then, I doubt any were used on a routine basis.

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Elminster
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 2:25 pm

On my todo list is getting my 8 inches working again (oo-er), when I do I could make up a cable to fit to beeb. So perhaps sometime in the next 40 years.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Sat Aug 31, 2019 3:08 pm

Elminster wrote:
Sat Aug 31, 2019 2:25 pm
On my todo list is getting my 8 inches working again (oo-er), when I do I could make up a cable to fit to beeb. So perhaps sometime in the next 40 years.
How you doing for working 8 inch floppies :wink: (diskettes I mean).

Mark

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by AndyF » Sat Aug 31, 2019 3:22 pm

BeebMaster wrote:
Sat Aug 31, 2019 11:50 am
The 8271 disc interface will support 8" drives, although as has been said, nobody seems ever to have used one. An additional modification to some links is required after fitting the 8271 upgrade - it's covered in 4.6 of the Service Manual.
Without going to look I'd actually always assumed given the datestamp on most 8271 chips being 1978 they were -originally designed- for 8 inch floppy drives. :)
Andy

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 3:37 pm

The 8 inch controller in my SWTPC is a FD1771, which later became the wd1772 used by later beebs.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Sat Aug 31, 2019 5:09 pm

According to Wikipedia, Shugart Associates introduced the ​5¼ inch FDD in 1976. And by 1978 there were more than 10 manufacturers producing such FDDs.

All I know is that the only floppy drives I saw in use between 1982 and 1985 was the 5¼ inch type.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by AndyF » Sat Aug 31, 2019 5:15 pm

I don't recall seeing one 'in use' aside from on old TV (War Games immediately springs to mind here) , I have seen one in the metal a long time ago but that's about it.

What would be (to me at least but I'm a bit boring perhaps?) would be to find out how their access times compare to a 5.25 as in how much slower they are, and also how much noise they make compared to a 5.25 as well. The latter I would like to know as its been a rare day that a 3.5 has been louder than a 5.25 so I suspect an 8 will be even more noisy.

Having said that the AMS/ZX/PCW 3"'s were not terribly quiet, I recall now seeing some advert for said 3" for a B in one of the mags too. Probably not a popular choice! :lol: :oops:

Back on topic again, the power consumption I'd suspect would be a tad more with the 8's too perhaps. Thinking here (without bothering with Google) that the magnetic density would be less too so it would likely be the 5.25 equivalent of SS/SS or DS/SD , as in single density only.
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Diminished » Sat Aug 31, 2019 5:20 pm

The Model B circuit diagram contains an extra clue, as it labels one logical output to the disc drives the "LOAD HEAD" signal.

"Loading heads" was apparently a process only relevant to 8 inch drives. 5¼ inch drives don't have any such mechanism; this signal is usually used instead to switch the spindle motor on and off.

(I am led to believe that 8 inch drives would run the spindles continuously as long as they were powered on, although I've never used one myself. This document has some good information about floppy drives. It proved useful for building this monstrosity.)
Last edited by Diminished on Sat Aug 31, 2019 5:33 pm, edited 2 times in total.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by iamaran » Sat Aug 31, 2019 5:41 pm

Someone in my class at school in the mid 80s had 8-inch floppy drives rigged up to his; I think he said his dad had obtained them. I can't give any other details except I recall they were in a cabinet of some sort and were huge.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by duikkie » Sat Aug 31, 2019 6:07 pm

I have use 8 inch floppy with discdrive it was a HP machine analytisch system

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 6:44 pm

1024MAK wrote:
Sat Aug 31, 2019 5:09 pm
According to Wikipedia, Shugart Associates introduced the ​5¼ inch FDD in 1976. And by 1978 there were more than 10 manufacturers producing such FDDs.

All I know is that the only floppy drives I saw in use between 1982 and 1985 was the 5¼ inch type.

Mark
I think my dad swapped from 8 inch to 5.25 around 82 (ish). So that sounds about right, people only usually swap once the new format has dominance due to hassle factor of changing.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 6:45 pm

Diminished wrote:
Sat Aug 31, 2019 5:20 pm


(I am led to believe that 8 inch drives would run the spindles continuously as long as they were powered on, although I've never used one myself. This document has some good information about floppy drives. It proved useful for building this monstrosity.)
That is right it is a bit disconcerting.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 7:05 pm

Looking at all my 8 inch documentation it was all written around 1978. Interestingly I have recorded if I have any documentation on the disk controller card (could be in the main documentation). Will have to dig it all out again. https://elminster.github.io/swtpc/swtpc_docs.

I do remember my controller has both 50 pin 8 inch and 34 pin 5.25 inch drive connectors.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Sat Aug 31, 2019 7:10 pm

Were the spindle motors in 8 inch drives AC type motors?
If yes, then I’m not surprised they ran continuously while powered up.

Winchester hard drives of the era I believe were the same in that they ran continuously while powered.

Mark

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sat Aug 31, 2019 8:53 pm

Not sure what type I have. I have the manual for both DRE/DRI Model 76 (technical manual) and model 7200 (user manual), but look similar.

45watts each, so 2 of them is eating 90watts. Won't be powering those of the Beeb's supply.

They have both AC (240v) or DC (5v & 24v) input. But it does say:

- Apply power
- Wait 2 seconds for spindle speed to stabilize
- Insert disk etc.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by FourthStone » Sat Aug 31, 2019 9:05 pm

Our econet server had two 8 inch drives, one for the OS and one for data mounted vertically along with the other logic components in a largish metal case.

No other details and I wish I'd stayed in contact with the teacher in case there was a chance to snap up some of the kit when it was replaced :-k

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Coeus » Sun Sep 01, 2019 12:16 am

1024MAK wrote:
Sat Aug 31, 2019 7:10 pm
Winchester hard drives of the era I believe were the same in that they ran continuously while powered.
I wonder why that changed. I could take a guess. Hard discs should be fairly low friction. While I believe floppies are made to keep the friction down one can feel a little resistance so I suspect there was a problem with excessive wear.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Sun Sep 01, 2019 1:27 am

Energy saving as well as wear.

Also, modern drives are far faster to get up to speed compared to the older drives. The older Winchester hard drives needed a couple of minutes before the speed was stable.

I’ve not actually timed it, but modern 3½ inch drives appear to be quicker to get to speed than the 5¼ inch drives. Or is that just me?

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Elminster » Sun Sep 01, 2019 8:25 am

Well if my 8 inches take 2 second for the spindle speed to stabilise just imagine how annoying that would be if they did that ever time you started to access the drive on a disk based O/S like CPM or Flex.

It is why one of my projects is to get the sdcard solution up and running on the SWTPC.

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by BigEd » Sun Sep 01, 2019 8:30 pm

It makes sense - no stepper motors, so slow to get a stable spin speed, so best to rotate constantly, and then use the head-load signal to bring the heads to the disk only when needed. Less wear!

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by AndyF » Tue Sep 03, 2019 1:30 pm

What is the formatted capacity of the 8's please ? When used on a BBC that is.

I'm going to assume its limited to 40 tracks, so based on what a 177x (as I don't have an 8271 to hand at the moment and BeebEm is having other ideas) would do its likely limited to 101888 bytes / just under 100Kb.

I'm unsure if that's D-Density or not though! I can't see it being single as that would likely reduce it to 50Kb per 'side' :shock:
Last edited by AndyF on Tue Sep 03, 2019 1:31 pm, edited 1 time in total.
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by Kazzie » Tue Sep 03, 2019 1:39 pm

The formatted capacity is a function of the number of tracks, the modulation (FM only for the 8271, MFM available on the 1770 with ADFS), and the filing system used.

So if you're sticking to DFS and deciding on 40 tracks, you'll end up at the same capacity of 100kB per side as you would on a 5 1/4" floppy. (At least that's what a quick brainstorm tells me.)
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1024MAK
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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by 1024MAK » Tue Sep 03, 2019 2:45 pm

For general disk capacity see here and here...

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by gtoal » Sat Sep 07, 2019 11:54 pm

I have a patch for the DFS rom that supports 8in disks. Written by Fred King. Will upload it here as soon as I can get it off an old floppy image in a couple of days. Supports 77 tracks if I remember right.

G

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Re: Hmm.. was there ever an 8" floppy drive for the BBC?

Post by gtoal » Tue Sep 10, 2019 6:34 pm

Could some kind soul please extract the contents of D1000.IMG and D1000B.IMG from http://gtoal.com/bbc/ ?

Judging by the text strings I see in the image, that is likely our 8 inch formatter and modified DFS.

(I'm not in a position to extract files from a disk image yet)

thanks

Graham

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