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Accessing two 1541 drives

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stangman517

Experienced Member
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Dec 15, 2014
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Location
Georgia, USA
Hello!

I recently (new comer to C64) bought a nice C64, and found two good 5 1/4" drives. Both drives appear to be working when I connect them one at a time. I can write to one diskette, hook up the other drive and both drives read the same diskette I save a .bas file to. This at least seems they are both in the same and/or correct alignment.

Confusion: when I hook both drives up via the serial port and I type: => LOAD "$",8 and then LIST it displays the directory, but when I type: ==> LOAD "$",9 and LIST it fails to read the 2nd drive. It displays "Device not present Error."

Also when I type OPEN15,8,15:pRINT#15,"N:SHM,0":CLOSE15. This will format device 8 fine. However, if I type OPEN15,9,15:pRINT#15,N:SHM,1":CLOSE15 I expect it to format the 2nd drive but it doesn't.

So how do I talk to the 2nd drive?

Thanks
 
You have to cut a jumper inside the unit to make it permanently device 9, as they are all 8 by default. You should be able to Google for the 1541 user manual which mentions this.

You can also issue a command to temporarily change one of them to 9, but only until it gets reset. This should also be easily Googled.
 
Find a copy of the three or four line basic program that causes the computer to reassign drive 8 to drive 9. Save this program to a disk. Verify it works, with only one drive attached to c64.

1. Set up system with two drives attached, but boot with only one drive powered on

2. On the disk in the running drive, load/ run the drive 8to9 program you have stored there.

Now the one powered on drive thinks it's drive 9

3. Power on the 2nd drive which by default thinks it's drive 8

That's a good way to use two 1541s without making permanent hardware changes
 
Hello Bill.

Yeah I will try it the software method and YES save the pgm. I was lucky enough to receive a 1541 disk manual with a VIC 1541 I bought recently and it mentioned the software method. Haven't looked at it yet, but does appear to be the safest. I found one link where it talks a bit more of cutting the jumpers just outboard of the 6522 chip (I guess this is the CPU). When I look at it and read what's in the manual and what's in this link it still isn't clear to me HOW to cut the jumpers and what EXACTLY they look like. Here's a piece of what it says:

"Each jumper is a thin line of aluminum which connects two aluminum-colored semicircles. Use a knife to scratch through both jumpers."

Ok so I think I've identified the two aluminum semicircles BUT not sure about the "thin line of aluminum." I see a very TINY thin line of aluminum just between the semicircles but not sure if this is the line to cut. Last night I decided I will not cut NOTHING unless I know 100% it's the correct line to cut. Actually I haven't tested the VIC drive until last night and it wouldn't read diskettes. I'm assuming it's an alignment problem. I bought software to align the drives and it came with CD with instructions, AND hopefully a video for us lay people with component level experience.

When I open two drives the VIC and Commodore 1541 drives PCB is not the same, so I said YEP the software method is safest for me for now.

Thanks Bill and Wittage for your advice.

Spencer

Here's the link: => http://dallasdenny.com/Writing/2013/07/21/commodore-15401541-disk-drive-modification-1984/
 
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this is the perfect example why one should avoid hardware changes to 1541 drives unless you install an external switch to make it easy to revert back. If you were to change the working drive to "9" and then find the other as drive 8 was bad, you'd be stuck.

Another benefit to the software method - you can first load diagnostic programs on a working drive, then switch it off. Attach the non working drive and run the software tests. Because you already had the program in memory, it will work and you can test the bad drive. Gets you around the chicken/egg problem - if your drive was ok in the first place no need to load a repair program.

NOTE - newer drives (1541-II, 1571, 1541-C) have dip switches on the back so you can set the drive assignment without using to make permanent changes to hardware NOR run the software program to re-assign.

Bill
 
Doing the software method is my action of choice - for now. I'll have to look at my other drives for the dip switches.

So one question for anyone. If I have two 1541s connected can I then use the "DUPLICATE" cmd to make backup copies of some old C64 pgm. disks? These disks at 30+ years old have to be reaching a mtbf, and I have no idea how much use some have actually had.

Thanks for all your answers!
 
IIRC programs designed to circumvent protected disks were referred to as nibblers. There are also several titles online that have already been cracked.
 
You cannot use the duplicate command. That is reserved for two-drive units, not two one-drive units.

There are commercial copy programs that will duplicate disks faster than you could otherwise, and copy copy-protected disks. I used to have several, and one I wrote. Unfortunately I have lost all those disks.

The one I remember best was called Renegade.
 
billdeg said:
But if all goes well he does have a two drive system, per the content of this discussion
Click to expand...

He has two one-drive units, not one two-drive unit like a 2040 etc.

DOS disk duplication only works in the two-drive units. The drive controller copies directly from one disk to the other; the heads move synchronously.

The only advantage of using two 1541s instead of one for copying disks is the lack of disk-swapping. It's still horrendously slow.

It is possible to install software into a 1541 to make it copy directly from another 1541 without using the C64, but if I recall correctly the only advantage was not tying up the C64; it was slightly slower than copying via the C64 the normal way.

It's theoretically possible to add a second drive mechanism to a 1541 and change the ROM. There was an article about that round 1989 or so.

Back when I was copying disks a lot, I only had one drive so I don't recall if any of the commercial duplication software that I had would work with two drives or not. But either way, it was significantly faster than the standard copy utility that came with the 1541, which I think was written by Jim Butterfield, and if course usually meant copying copy protected disks.

Memory says that another popular program was called Maverick.
 
Maverick was a good 'un. I have that around here somewhere, but I tend just to use Fast Hack'em for quick copies and nibbler copies. Virtually all the commercial copy utilities will handle two devices, including those.

That said, I have an MSD dual drive for the few times I need to do lots of repeated duplication work.
 
KC9UDX said:
It is possible to install software into a 1541 to make it copy directly from another 1541 without using the C64, but if I recall correctly the only advantage was not tying up the C64; it was slightly slower than copying via the C64 the normal way.
second drive mechanism to a 1541 and change the ROM. There was an article about that round 1989 or so.
Click to expand...

I've been thinking about this and wondering why that would be. It should be faster, especially since the drives could both be put into 1540 mode.
 
Thanks ClassicHasClass.

I found a link on Fast Hack'em (if anyone wants it let me know; didn't know if it's ok to post here). It offered versions 1.9, 4.5, 9.5.

Something in its blurb that sounds slick to me: "In later versions of Fast Hack'em, disk copying could be performed without the computer if two Commodore 1541 disk drives were available. The software would be loaded with a Commodore 64, the two drive option would be selected which transferred software to the drives' controller memory, the serial cable could be disconnected from the computer. Any number of copies could be performed as long as neither drive was powered down."

So what is the RAM in these drives? To be able to disconnect the serial cable from the C64 sounds pretty slick to me.
 
stangman517 said:
Thanks ClassicHasClass.

I found a link on Fast Hack'em (if anyone wants it let me know; didn't know if it's ok to post here). It offered versions 1.9, 4.5, 9.5.

Something in its blurb that sounds slick to me: "In later versions of Fast Hack'em, disk copying could be performed without the computer if two Commodore 1541 disk drives were available. The software would be loaded with a Commodore 64, the two drive option would be selected which transferred software to the drives' controller memory, the serial cable could be disconnected from the computer. Any number of copies could be performed as long as neither drive was powered down."

So what is the RAM in these drives? To be able to disconnect the serial cable from the C64 sounds pretty slick to me.
Click to expand...

It's not just RAM. Each drive contains a whole computer, roughly equivalent to a VIC-20 without the VIC chip.
 
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