XM1541 cable makes C64-SX freak out.

[timbob]

Hello there!

I've got myself a really nice Commodore 64-SX, and i wanted to connect it to my PC. After some searching I found a site on how to make your own Xx1541 cables (Which most of you probably already know)

So i made myself this one:
http://sta.c64.org/xm1541.html

But it doesn't work!
I checked the description and several readme files of programs like star commander and openCBM, and it should work with the internal diskdrive of the SX.

However, after plugging in the cable, the commodore freezes when turned on.

If I turn on the commodore first and then the PC, the commodore loads as normal, but after the PC has booted, some glitches appear on the commodore, and it freezes while the disk drive keeps on spinning.

If i turn on the PC first and then the commodore, the screen becomes white and the disk drive keeps on spinning too.

I checked all of the connections, multiple times. changed the diodes but still it does nothing...

Is there something wrong with my parallel port settings? Did I make the wrong cable?

Any clue on how I can fix it?

 

[carlsson]

Have you tried POKE 56576,199 on the SX-64? This releases the computer part from the IEC bus by setting CLK high. You can use it as usual afterwards, just remember this POKE before everytime you want to access the drive from the PC.

The same phenomenon would occur if you connect the XM-1541 to a regular 1541, the connect a C64 to the other IEC connector on the 1541. You simply can't have two "master" devices using the bus at the same time.

Btw, if I find the time I can try to replicate your setup as I also got a SX-64 and a XM-1541 cable. I can't promise when I get to do it though.

 

[timbob]

The moment the cable is connected and I turn the commodore on, it doesn't even boot.

The screen is just completely white, and it won't respond to anything I type or do.

Should I Poke it first, and then plug in the cable?
Because I read somewhere you shouldn't connect cables after the machine is turned on...

 

[kb2syd]

What about changing the internal drive or disabling it

DRIVE SELECT JUMPERS:
     Disabling the internal drive can be used as a diagnostic check
(example: when you're not sure what is "locking up" the serial port).
To disconnect the internal drive (and make it "invisible" to the
computer) so an external drive can be used as device 8, unplug P19, a
(six wire: five white and one black) cable on the FDD board, or the
other end at P11 on the I/O board.
     If you simply want to change the device number of the internal
drive, there is a set of jumpers on the FDD board, just as you would
find inside a 1541. They are located near P22, the 2 wire connector for
the drive reset switch.

FDD board top edge--||------------------||||||----------
                    ||                  ||||||
               P22 [||]  (2) (1)       [||||||] P19
                         drive select
                           jumpers

As in the stand-alone 1541, the SX drive has both drive jumpers closed
from the factory, so the drive is device #8. The jumpers, by the way, 
are the two tiny silver half-circles with a bar in between them. To open 
a jumper, cut the bar between the half-circles with an Xacto knife. To 
close an open jumper, apply a blob of solder to reconnect the 
half-circles. To change the drive to device #9, cut jumper 1. For device 
10, cut jumper 2, and for device 11, cut both jumpers. If you want to 
add a drive select switch, each wire of the added switch will go to one 
side of the cut jumper. If the solder pads are damaged, you can wire 
directly to the IC pins. Jumper 1 grounds pin 15 of IC UBC3 VIA on the 
FDD board and jumper 2 grounds pin 16 of that chip.

 

[dave_m]

What about changing the internal drive or disabling it

As Anders mentioned, the real issue is having two Masters (PC and SX-64) not two floppy drives. One floppy should be configured device 8 and the other device 9.

I have no knowledge about the safety of hooking up cables on a powered Commodore.

 

[MikeS]

The moment the cable is connected and I turn the commodore on, it doesn't even boot.

The screen is just completely white, and it won't respond to anything I type or do.

Should I Poke it first, and then plug in the cable?
Because I read somewhere you shouldn't connect cables after the machine is turned on...

Huh? I thought you said if the PC 's turned off, "the commodore loads as normal"???

 

[timbob]

Huh? I thought you said if the PC 's turned off, "the commodore loads as normal"???

Yeah, sorry, that's what i ment.

The commodore loads as normal when the cable is plugged in, but when the PC isn't turned on.

The moment the PC is ON, the commodore won't work and i get a blank screen.
So as long as i've got two working machines connected, something goes wrong...

 

[MikeS]

Yeah, sorry, that's what i ment.

The commodore loads as normal when the cable is plugged in, but when the PC isn't turned on.

The moment the PC is ON, the commodore won't work and i get a blank screen.
So as long as i've got two working machines connected, something goes wrong...

Ok, so you can try the poke with the cable connected but the PC turned off, and then turn on the PC, right?

I assume that this has been done (PC<>64SX), and that the internal drive is still on the bus, even though it's internally connected?

 

[Chuck(G)]

I've used the XM1541 was to connect a 1541 (or 71...etc.) drive to a PC to be able to read/write disks.

All parallel ports are not created equal. Later systems use CMOS for the drivers and that could be the problem.

 

[timbob]

Hi everybody!
Sorry for the late reply, I've been a bit out of business lately, so to speak.

Anyway, I'm picking up where I left, and it still doesn't work

I've got a different PC now, but the same problem...
This time, I plugged in the XM cable in both computers, turned on the 64-sx and used the poke command (I tried both poke 56576,199 and the poke56576(peek(56576)AND239) )
after that I turned on the PC

It looks good for a few seconds, but after a while, as the bios of the pc is loaded, the screen of the 64-sx gets glitches again, and the diskdrive starts spinning.

I'm kinda clueless now where to look... I don't have an older pc lying around to test it.. and the cable looks ok, checked it several times...

What to do? :eh:

 

[dabone]

Do you have a grounding problem between the two machines?

(And no way you can just pick up a 1541 cheap?)

Later,
dabone

 

[barythrin]

Could it be the configuration of your parallel port on the PC causing any issues? Do you know what mode it's set to in the BIOS?

 

[carlsson]

if I find the time I can try to replicate your setup

Apparently three months is not enough time to get me going. Now that the thread has been bumped, I'll see if I actually can manage to conduct some testing myself, perhaps in a week or so.

 

[timbob]

Do you have a grounding problem between the two machines?

(And no way you can just pick up a 1541 cheap?)

Later,
dabone

I don't think it's a grounding problem, because the first few seconds the computer is on, and the bootscreen is showing, the commodore just acts normal. It's only when the pc starts to load windows etc, the commodore freezes.

If it was a grounding problem, the commodore should freeze the second the pc is turned on... but i could be wrong.

in the drawing here:

it says pin 2 on the DIN and pin 18 - 25 on the D25 are ground. Should I or shouldn't i connect those to the outer part of the plug? (the metal shell, so to speak)

 

[carlsson]

I am not entirely certain, but I can't remember connecting any shield in my home made XM-1541 cable. Actually I made it from CAT5 UTP cabling but it should not make any difference.

However it is true that while you load Windows, my 1541 connected to the PC goes busy until Windows is finished loading. You really should try to get ahold of an external floppy drive, even on a loan to verify that your cable, parallel port and software installation (which itself can cause some grief) all are OK before tackling the slightly more complex problem of connecting the SX-64 to the PC.

 

[timbob]

True, it would be nice if I had a 1541.. Even if it doesn't work on my SX, i can still burn some flops
But, untill i find one, I'm gonna keep trying to get my SX working...
(I wouldn't know where to loan one, so I'd have to buy it, The people i know don't even know what a commodore is..)

Could it be the configuration of your parallel port on the PC causing any issues? Do you know what mode it's set to in the BIOS?

I checked the bios, It was in ECP, Also tried it in normal, but same problem..
I could choose between ECP, EPP, Normal and Bi-directional. (and i don't have a clue yet, what the difference is)

 

[barythrin]

Not sure if this is helpful but just to clarify it's as soon as the PC turns on (bios screen) the system acts up right, not just at the operating system loading? or is it the OS playing with the port to check for things? I had read one post on lemon64.org which had commented they had an issue when the parallel port wasn't a certain setting, but then another post said a different mode than that and theirs was working fine so I kinda shrugged that off but you could certainly try playing around with those settings on the PC. I don't have one of those cables or I could figure out where my systems were and test it too.. any other folks near him that could help out? Or maybe even someone on the lemon64 forums might be near by or have seen that error (though I saw a lot of posts there quoting Anders so you may be just as well off here ;-) ).

 

[Chuck(G)]

You didn't perhaps hook the diodes in backwards, did you?

 

[timbob]

Hi there!

I've made some progress here
Someone traded me a c64 with 1541 and a tapedeck for a bag of appledonuts!

And I made a ms-dos disk to boot, which seems to help a bit.

If I start the pc, in dos mode, the drive of the sx or the 1541 won't start spinning like before.
If I then load starcommand and select drive 8, the 1541 drive turns on and spins, so there is some sort of communication, however, it does give a time out...

I did check the cable again, but it looks fine...

Any more ideas?

I'll keep on tinkering for a while, because it looks like I'm getting closer

 

[carlsson]

Did you only check the cable for continuity, or did you also check that you soldered the right wire on the right pin? Recently I had some problems with my old XM cable but it turned out to be one wire in the DIN end that had come loose, plus the power cable also had one loose wire. Once those two were secured, it worked with a 1541-II. However regretfully I haven't yet lugged out my SX-64 to test it with the cable.