+3 and amstrad 6128 disk b port compatibility question
After having read many web pages, secarica's long text and guesser's ascii-art diagrams for connecting a pc floppy to +3 drive B slot, I found myself very unsecure about building the cable. Then I searched for the amstrad 3" diagrams, and there is a very detailed and photographed step-by-step guide, very suitable for my MSwindows-wizard dominated brain.
http://www.cpczone.net/boards/viewtopic.php?t=1385
the question is, is this guide also works for an +3?
http://www.cpczone.net/boards/viewtopic.php?t=1385
the question is, is this guide also works for an +3?
Post edited by Arda on
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yes, it's the same cable, same unit, same behaviour. You can use above guide to connect your floppy drive to your +3, you can use http://www.cpcmania.com/cpcdiskxp/cpcdiskxp.htm (cpcdiskXP) package to read/write DSK images to a floppy disk. Tested and working.
tags for future searches: zx spectrum +3 drive b cable pc floppy dsk image
The only downside i can see to that is that the +3 will think that a disk is always inserted, and therefore give an innacurate error message if its not. I also seem to remember its possible to send +3DOS into an endless loop if the disk isnt there.
(My solution is to fake the ready signal by soldering to the disk inserted switch and a bit of TTL)
You just need one old-style floppy cable (that one with five connectors, two 5.25", two 3.5" and one for motherboard). Just consider the connector for motherboard and put it into the drive, with red cable "far" from power supply (unlike you connect on PCs) and the 5.25" connector nearest to it, plug into the +3 port. The key present in the cable should help you to put it in the right way. The rest of cable could also be "cutted".
You should put, in your drive, the connector with red cable far from power connector, because the Shugart +3 port has all pins inverted.
The drives should be powered by a PC-AT style power supply or a compatible PSU with at least +5V, 1.2A power.
It can be done to a point (with modifications) but again it won't be 100% compatible, some amiga games will not load, probably the protected ones.
So i should expect this incompatibility goes both ways.
It just might write and read the disks you wrote on it BUT will it read disks written on another pc type drive?
Write a +3 3.5'' disk (from a .dsk image) on your PC using the CPC making disk program that installs a low level floppy driver (on the PC). http://www.cpcmania.com/ (CPCDISKXP)
I expect the amiga floppy will not be able to read it.
no it's vice versa, i mean pc drives are not compatible with miga drives. you can create perfectly compatible pc disks with an amiga. so it is very possible to connect an maiga floppy to an +3 if they are pin compatible.
Hardware wise, Amiga drives are slightly different from both modern PC drives and Old PC drives (AKA Shugart compatable drives).
The important differences are with the "Ready" signal.
The +3 expects a Shugart compatable disk drive for Disk B.
You can use Amiga drives with the +3 by just re-wiring the cable, cos although the READY signal works slightly differently to a Shugart drive, it happens to be similar enough to work with the +3.
I cant say if it would work with the +D, cos i dont have one, and have never tried it. It depends as much on the +D firmware as the hardware.
Now, what that hack does is make the FDC think the disk is always ready by shorting the READY line to ground. The +3 does its own Spinup delay, and doesnt care about the ready signal from a timing point of view, it just uses it to detect if a disk is inserted.
However, the downsides to this hack are that the +3 will not be able to detect if a disk is inserted. Also, because READY is a shared signal, it will also stop the +3 detecting a disk in Drive A as well. However, as this signal is an Open Collector signal, you shouldnt do any damage to either drive by doing this.
The second downside, is that if you accidentally access a drive without a disk in it, you will lock up the machine, cos the Floppy controller chip will be waiting for an index signal, and as the READY signal is telling the FDC that the disk is rotating fine and everything is OK, so it wont error.
Basically the differences are:
Shugart: Has a READY signal. This goes low when:
- A disk is inserted
- The drive has been selected
- The drive is up to speed
Modern drives: Have a Disk Change signal.The big difference between Shugart drives and modern drives is this signal. If it is low, the disk is not ready for use. It wont go high again until:
- A disk is inserted
- The drive has been selected
- The drive is up to speed
- A step pulse has been applied.
Its number three that most old computers, including the +3 have an issue with.Amiga:
As well as detecting if there is a disk present, The Amiga uses its ready signal to indicate the density and type of a disk. This works with the +3 cos when the drive has a DD disk inserted, it happen to output all 1s on its diskchange signal, probably for simplicity's sake.
You wouldnt be able to connect an a 5 1/4 Amiga drive to the +3 this way, as its diskchange is different (I think it oscilates between 0 and 1, but cant remember), but they tend to be custom jobs anyway.
There is also some stuff about the drive latching the motor signal, however, that doesnt matter for the +3