high density disks

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
User avatar
mga1103
Posts: 184
Joined: Mon Jan 24, 2011 4:00 pm
Location: Galway, Ireland

Re: high density disks

Postby mga1103 » Mon Mar 07, 2011 1:40 am

MartinB wrote:Image It is safe to come out...? Has he got it working now...?
...

:lol: :lol: :lol: He...he...think I know how you feel!
MartinB wrote:...
You (Martin) said you used *OPT80,1 which is even more confusing since the second parameter is supposed to be the drive number but in the end you had the 35 as Drive 0 and so the *OPT would appear not to affect that drive. Most odd...

Good catch Martin! Actually interestingly, it doesn't matter whether you issue an *opt80,0 or an *opt80,1 before formatting a HD disk. As a test, I tried *opt80,1 on a freshly booted beeb and proceeded to format an 80-track HD disk in drive 0 without problem. (Also works if you issue an *opt80,0, as you'd expect).
MartinB wrote:...
Mark - Nice idea to roll up the HD facility in a 177x module. Not sure if you can get/create all the signals required without still using flying leads but well worth considering. You certainly have my blessing if you want to look at an upgraded version of your module.

Nice idea! This would certainly not hurt on the DataCenter marketing front! While it may not be possible to eliminate all the fly-leads, incorporating the logic into the dfs module would be a great plus! The essential "74151 logic" could become part of it and save folks having to build the MBM!
regregex wrote:Great hack Martin A! Welcome to the club :)
...
--G

To be honest, any praise is deservedly MartinB's... Couldn't have managed it without his relentless help! But, thank you nonetheless...!
MartinB wrote:...
I'll talk Martin A into an Acorn DFS 2.26 rom and then he will undoubtedly benefit from a more enjoyable HD customer experience. (Hey, if you can't beat cold-callers.... :wink:)
...

Ok, I'm talked into it! Send me an invoice for the rom - the business is yours! :wink:

-Martin (A).

Andrewcee
Posts: 19
Joined: Thu Sep 21, 2017 4:27 pm
Location: Swindon

Re: high density disks

Postby Andrewcee » Sun Oct 22, 2017 12:07 am

I have read this post several times - so much to take in. All good stuff, my thanks to all. Thought I'd have a go connecting a couple of Alps 35 floppies from the loft to a recently purchased Master fitted with Econet and VL1772 02PC - if only my old B had Econet, could be fun.

Proof of concept,...
1. Check with scope, confirm 8MHz on 1772 pin 18, 16MHz on Link b2 - correct.
2. Lift 1772 from socket, gently bend pin 18 up by about 30deg, lightly solder flying lead c. 8" long.
3. Push flying lead into link b2, 16MHz now on pin 18.
4. Set *CONFIGURE FDRIVE 1
5. DFS formats 80 tracks HD and 2HD on DFS2.24 under MOS 3.2, verifies, saves and reads.
5a. 2 of 3 floppies, had to do a 40 track format before the 80 track???
5b. DFS will not format on DFS2.45 under MOS 3.5???
...I've been on the case all day, been fun, something to look at another time.

Have Solidisk WD1770 with their 2.1J DFS & 2.1M ADFS in BBC with Solidisk 256/4Meg board. Their DFS will cope with multi-31 file catalogues (gets messy!) and can run double density. Have to have a look with ADI see what's going on. The 1770 is soldered in unfortunately, although thoughts of swapping for 1772 or maybe buying new board with 1772 02 02 fitted, possibly swapping out Solidisk DFS. Be great to get a 35 & 525 disk combination running on both machines.

Thanks for all the info - great help!!!

Andrew

User avatar
MartinB
Posts: 4555
Joined: Mon Mar 31, 2008 9:04 pm
Location: Obscurity

Re: high density disks

Postby MartinB » Sun Oct 22, 2017 7:02 pm

I’d all but forgotten about this stuff because when using my two development Beebs that both have the auto-density mod fitted, I don’t even notice if a given 3.5” disc is DD or HD - it’s that reliable and transparent for me. With HD 5.25 floppies I of course have to manually flick the drive density switch but I think I must do it without even noticing. Both of those Beebs are Acorn DFS 2.26-based and I although I never completely cracked HD ADFS, I never use it anyway through simple dislike! [-X :wink:

I did successfully trial the mod on a Master during the investigations but because I don’t use the latter very much, I can’t remember if there were any particular wrinkles or caveats although I don’t think there were.... :-k

If you don’t get sorted but can provide some good detail as to configurations and symptoms, I’m sure it can be resolved but I might have to re-read the thread myself as a refresher..... :)

Andrew wrote:5a. 2 of 3 floppies, had to do a 40 track format before the 80 track???

Because most HD floppy media has a PC heritage and may have been subjected to multiple and assorted magnetic lay-downs, I often find that if a given disc is troublesome or quirky like the two you mentioned, a quick scrub with my bulk eraser (below) sorts it out. (Indeed, even ignoring HD matters, this treatment can often bring any seemingly unusable discs back to life.)

bulk eraser.JPG

Andrewcee
Posts: 19
Joined: Thu Sep 21, 2017 4:27 pm
Location: Swindon

Re: high density disks

Postby Andrewcee » Sun Oct 22, 2017 10:51 pm

Good hearing from you Martin, and thanks for your reply. Thanks too for the mountains of info you've posted, couldn't have got my dual 35 set up working without your help!

Have dual 35 Alps drives running on Master as drives 0&1, think they work as 0-3 although more testing required. Alps drives easily modified to connect HD switch to pin 2, single track cut and jumper to 'large' solder pad on pcb sorts it. Can open a drive and post photos if helpful. Obviously, straight throught cable needed without PC pin swaps.

Formats DD & SD on HD disks under Watford on BBC B emulation, looks like it will do two-page catalogue also. Only the latest Acorn 2.45 DFS on Master not working, be great to fix it if I can. Acorn only reads/writes SD on HD disk under 2.24 DFS as best I can ascertain.

Thinking more about a 525 & 35 set up, why I wonder? Dual 35 set up far more useful. Drawn up truth table for switching dual set up, one limitation just now is both drives must run DD or HD floppies with using pin 2 on both. Hardly an issue as will use HD all the time.

Have pair of Teac 525 40 track drives which will do DD under ADFS, but must run the 8MHz clock. Have couple of Mitsubishi drives in old BBC, but still to investigate. I know they double sided and will do DD under Solidisk DFS, and ADFS of course.

Just getting into all of this, still more to learn, mistakes to make, and ideas to try out. Mouser order in this evening for logic gates to build a version of your MDM. Hopefully later this week will be up and running on Master with auto-switching on dual 35 drives, with option to swap to dual 525 as required. Have to check few things first, although expecting it to auto switch on 35 yet remain fixed on 8meg for 525 drives.

Once Master sorted, will move on to my dear old Beeb. I've blown it up more times than I care to remember, yet always managed to fix it, hence the number of sockets now in the board. Most used reference books; my TTL and 4000 series, can sort most things with a scope and one or other books. Thinking I'll keep the dual 525 Solidisk set up which has worked so well In the past, but go for the dual 35 set up on the Master. Solid state memory cards via the PC likely the first step for copying files between the two. Love to get Econet / Ethernet working on both, Econet fitted to Master. Ordered some Raspberry PI gear this evening too so as to have a look at copro emulation, sounds like fun?!

Enjoying playing again after so many years, memories of my writing and building a power station performance monitor on a Master with Winchester (remember those?) during my working life, and building my own prom programmer using mixture of basic and m/c code which was damned fast, even if I say so myself. Lots more fun to come....!!

Andrew

dominicbeesley
Posts: 464
Joined: Tue Apr 30, 2013 11:16 am

Re: high density disks

Postby dominicbeesley » Mon Oct 23, 2017 2:26 pm

I've been reading this thread with interest and I'm going to have a play at some point. I have a question about pins 4 and 2 on the floppy cable.

Was there consensus that this was used consistently on 3.5" drives as an output?
For 5.25" HD this is an output, does it switch both connected drives?
If I added an open collector driver to pin 2 for 5.25" HD switching would that fight with any connected 3.5" drives?

D

User avatar
MartinB
Posts: 4555
Joined: Mon Mar 31, 2008 9:04 pm
Location: Obscurity

Re: high density disks

Postby MartinB » Mon Oct 23, 2017 4:45 pm

Nightmare scenario - a flurry of rekindled interest in something you devised but last looked at 6+years ago.... :shock: :lol:

Jumping first to the final (v2) mod schematic....

Acorn 177x HD media mod V2.JPG


....there are separate HD inputs to the host computer (Beeb, Master or Elk) for drives 0 and 1 (as physical units so covers 0/2 and 1/3) and at the drive end I deliberately hijacked two lines which are, on the Shugart 34-pin 'standard', Pin 2 : Density Select/Status and Pin 4 : Reserved. I say Pin 2 is Density Select or Status because it's use has changed over time from density select input to the drive to selected density status output from the drive. However, importantly, in the case of both pins I have mandated that the the interface contact must be isolated in the drive such that we can take over their function as density status outputs. Typically, you will find that Pin 4 is unused on all drives (and is certainly not required for Acorn use) so simply cut any associated track at the drive connector and for Pin 2, you will find that it will be either unused or will have a jumper setting to allow it to be Not Connected, Density In or Density Out. As with Pin 4 though, it isn't used in the Acorn FDD implementation so again, just isolate it for use as a density status as described in the thread - either automatic for 3.5" drives or manually switched for 5.25" drives.

In summary, for my mod there are two density inputs to the host, one for each physical drive. They are mutually exclusive and the 177x FDC will only be clocked at 16MHz when the given physical drive is accessed (Motor On True) AND HD is selected for that drive. Therefore, your Drive 0(2) unit should use interface Pin 2 to report HD media inserted and your Drive 1(3) unit should use interface Pin 4. In both cases, DD media inserted is indicated by a logical Lo (0v) and HD media inserted by a logical Hi (+5v).
Note : When using two physical drives, you should always isolate Pins 2 and 4 on both drives even though a given drive will only be using one of the two as the media density-type signal. This will ensure that no inadvertent conflicts can occur if a particular drive is trying to use pin 2 or 4 for another purpose or has either signal tied hi or lo.

So, to answer your specific question Dominic, adding an OC pump in the disc drive output wouldn't be a problem noting though that I have specified a 10k pull-down in my mod circuit for each of the two density signals from the drives.

Andrew wrote:Thinking more about a 525 & 35 set up, why I wonder?

For the love of floppies - 5.25" drives are wonderfully tactile machines... =D> 8)

and wrote:Drawn up truth table for switching dual set up, one limitation just now is both drives must run DD or HD floppies with using pin 2 on both. Hardly an issue as will use HD all the time.

No, not necessarily. If you read my reply to Dominic above, this is why I specified hijacking interface Pin 4 for the second physical drive unit. With my set-up, I freely copy between different density media in the two drives.

dominicbeesley
Posts: 464
Joined: Tue Apr 30, 2013 11:16 am

Re: high density disks

Postby dominicbeesley » Tue Oct 24, 2017 11:08 am

Thanks for the info Martin, I will have a play with this. I was hoping it wouldn't require modding the drive, it's a shame that they didn't multiplex pin 2 i.e. only pull it low/high when that particular drive is selected...

I need to go on a mining expedition in my storage unit to find my store of floppies and the old HD 5.25" drive in my original 1993 vintage Linux box.

D

User avatar
MartinB
Posts: 4555
Joined: Mon Mar 31, 2008 9:04 pm
Location: Obscurity

Re: high density disks

Postby MartinB » Tue Oct 24, 2017 6:48 pm

Dominic wrote:I was hoping it wouldn't require modding the drive

Well, you don't have to mod the drives at all if you're ok with manually-switched media density selection for both drives. The two drive HD media inputs to the new mod board could simply be brought out to switches external to the Beeb and whenever you use a HD disc in a drive, you would simply set the corresponding switch for that drive to HD. This is how the 5.25" HD selection works in my suggested implementation anyway but with the switch located on the drive itself. I originally wanted as much automation as possible but because 5.25" drives don't have a physical HD media sensor, full automation can only be achieved with 3.5" drives. If you did use a manual arrangement, you'd just leave all the Pin 2 & 4 connections alone as they do nothing in the Acorn disc interface implementation anyway which is why I could hijack them for my purposes.

Andrewcee
Posts: 19
Joined: Thu Sep 21, 2017 4:27 pm
Location: Swindon

Re: high density disks

Postby Andrewcee » Thu Oct 26, 2017 5:40 pm

V2 MDM built & installed in my Master, can clearly see switching on scope between 8 & 16 meg. Thanks Martin!!
Attachments
IMG_3191.JPG

User avatar
MartinB
Posts: 4555
Joined: Mon Mar 31, 2008 9:04 pm
Location: Obscurity

Re: high density disks

Postby MartinB » Thu Oct 26, 2017 8:05 pm

No worries and nice job Andrew! =D>

So are you happily formatting, writing and reading HD media now?

Andrewcee
Posts: 19
Joined: Thu Sep 21, 2017 4:27 pm
Location: Swindon

Re: high density disks

Postby Andrewcee » Fri Nov 17, 2017 10:48 am

Hi Martin, Yesterday folded & sprayed some ali sheet and mode a housing for a couple of drives, made data & ps cables, and all is working well. Had to do some 'head aligning' on one of the drives, but now the three drives I have will each read/write disks from one another. Next job is to work out why I can only get the drives to work with MOS 3.2 / DFS 2.24. Be great to get everything working on MOS 3.5 and a later DFS. Enjoying learning and finding out!

Andrewcee
Posts: 19
Joined: Thu Sep 21, 2017 4:27 pm
Location: Swindon

Re: high density disks

Postby Andrewcee » Sun Dec 03, 2017 10:33 am

Can now use both 3.5 & 5.25" disks with mod fitted - not at same time, at the moment - at 'flick of a switch'. Fitted toggle switch to select the 16meg clock mod input to either 16meg for 3.5" drives or 8meg for 5.25" drives. Switched to 5.25"/8MHz Master/BBC runs as originally built.

User avatar
MartinB
Posts: 4555
Joined: Mon Mar 31, 2008 9:04 pm
Location: Obscurity

Re: high density disks

Postby MartinB » Sun Dec 03, 2017 1:06 pm

Good work! =D>

I have a manual switch on my 5.25” drive whilst the 3.5” auto-switches depending on whether I insert a HD or DD disc and I can therefore have any combination of DD/HD media in the two drives. I’ve basically just forgotten it’s there tbh and the only time I need to care is if I’m sending a disc to someone else who hasn’t got the HD facility.


Return to “hardware”

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 5 guests