cpm software detects 2 drives, but I only have 1

[lost84]

Hi guys,

Using the CPM sw its says I have an a and b drive. I only have a 3.5 that I fitted and its set to a. Works fine for everything else. The problem causes CPM to crash. Is this a hardware problem or software?

Any help is appreciated :-)

[TFM]

Do you have a special version of CP/M?

[AMSDOS]

Are you using CP/M 2.2 or CP/M Plus or something else I don't know about? Both 2.2 or Plus will detect how many Disc Drives are there, usually it's between 1 or 2.

[TotO]

I suggest that the ribbon cable device ID set both drives when you switch to external A.
Is, |B command under BASIC allow you to see the same floppy content when you make a |DIR ?

[arnoldemu]

Hi guys,

Using the CPM sw its says I have an a and b drive. I only have a 3.5 that I fitted and its set to a. Works fine for everything else. The problem causes CPM to crash. Is this a hardware problem or software?

Any help is appreciated :-)

is the disc motor always on?

Does the computer think the drive is always ready? (type CAT without a disc in and if it hangs it things it's always ready).
Or does it think it's always write protected?

[Badstarr]

A long time ago I accidentally connected the drive B select signal and drive A signal to the same drive. It seemed quite handy at first as I could make the drive function as both A and B or so it seemed. It led to erratic behaviour especially in CPM so I had to set the connections correct. It may be that your drive is receiving both A and B select, either a problem with the IDC cable or possibly the drive itself.

[lost84]

Hi guys, tried |b and that does not see the disk.

So I think the floppy is OK. CPM is ver 1. I downloaded it from this forum. Maybe I should try a later version, if I can find one.

[lost84]

Ps cat without disk works as expected.

[Badstarr]

When I installed a 3.5" drive on my 464plus there was two motor enable signals, one for drive A and one for B. It still could be that both drive enable signals are somehow routed to the same drive but the motor enable is not connected for drive B which would result in an unsuccessful read when you select drive B, as the drive won't spin up. Did you carry out any modification to the drive when you fitted it? Did you follow any particular guide?

So my suggestion would be, try another version of CPM and see if everything works as expected. If things are still going wrong report back and I'm sure we will think of something else to try. I would imagine if Bryce spots this thread he will be able to zero in on the problem in a snap.

[Bryce]

I've already read the thread, but my knowledge of CP/M is limited (ie: Zero), so I don't think I can help much.

From a hardware point of view: How is the 3.5in drive connected? Is it connected to the internal header or the external port? What cable are you using?

Bryce.

[lost84]

Its using an internal cable from urban retro. The cable has been modified by me to provide a ready signal and a switch to change the disk side.

[Bryce]

Convert the drive to send the ready signal and get rid of the ready jumper, that will make things easier and avoid CP/M and AMSDOS issues. This is most likely what's causing the issue. CP/M is probably selecting B and testing for a ready signal. Your ready jumper is telling CP/M that a disk is in the drive even when B is selected.

Bryce.

[lost84]

Thanks Brice, will do

[TFM]

Convert the drive to send the ready signal and get rid of the ready jumper, that will make things easier and avoid CP/M and AMSDOS issues. This is most likely what's causing the issue. CP/M is probably selecting B and testing for a ready signal. Your ready jumper is telling CP/M that a disk is in the drive even when B is selected.

Bryce.

That's exactly correct. CP/M does indeed sense for a set Ready signal, if it finds one, then it assumes (usually for good reasons) that there is a drive.


Now if you set the Ready signal ON by default, then any drive will be found, because everything is 'Ready' all the time.

[lost84]

Thanks Brice, will do

That's exactly correct. CP/M does indeed sense for a set Ready signal, if it finds one, then it assumes (usually for good reasons) that there is a drive.


Now if you set the Ready signal ON by default, then any drive will be found, because everything is 'Ready' all the time.

But I only have one drive connected.

[lost84]

Just noticed that when I do |b the floppy does make a sound like some things happening before returning "bad command".

In cpm+ if I try to change to the b drive I get the error invalid drive, bros function = 14

Also realised I'm using cpm2.2.

Being new to this I didn't know cpm2.2 and cpm+ came with the cpc6128, and cpm+ is v1.

Hope that makes sense!

[TFM]

You cut the Ready signal short, so it's always on for all drives. Your cable provides the Ready to the FDC, doesn't matter which drive you select.


Well, CP/M Plus displays v1.1 (or 1.0) but it's actually CP/M 3.0 or 3.1. It seems to be able to sense the problem as AMSDOS does, but CP/M 2.2 seems to crash, because it't not prepared for the crazy all time ready READY.


As Bryce suggested, try go get the Ready working on the B-drive itself and don't use that short cut cable. 

[lost84]

My eyes have been opened! Thank you sir.

[TFM]

I wish you all the luck! Let's hope its only that Ready signal and nothing worse. 

[lost84]

I have a matsumi drive, it looks like I need to move a smd resistor. Not messed with smd's before, but will give it a go.

Is it also possible to fool the drive into thinking the disk is low density, so I don't need to do the tape thing? Any thoughts on whether this is worth doing at the same time.

[Bryce]

Yes, the SMD resistor needs to be moved, but it's only a bridge (short circuit), not a resistor, so you can remove the existing resistor and just use a wire to short the other pins. You can also sort the sensor for DD/HD and it will think all disks are DD.

Bryce.

[TFM]

But he wants DD not HD 

[lost84]

Hi, the drive is more modern than any guide I can find. I'm bottling out of this one as I'm sure I knack my drive trying. Maybe the simplest option is to put a switch on the ready signal (via the cable) so I can manually switch it off.

[TFM]

Better get a well drive which can handle the Ready signal properly. Shouldn't be more expansive then 5 Bucks.

[Bryce]

But he wants DD not HD 

Oops, meant DD. Post edited.

Bryce.