Author Topic: more than 2 drives  (Read 2236 times)

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Offline radu14m

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more than 2 drives
« on: 09:43, 01 September 13 »
I would like to keep all the time all the drivers connected to my cpc6128.
- Internal drive A 3'
- External one 3.5'
- HxC.
Is it possible ?
The HxC would be assigned as drive c?
What kind of cable is needed ?
 
thanks !

Offline archcosmo

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Re: more than 2 drives
« Reply #1 on: 16:18, 02 September 13 »
hi there

the short answer is yes, is possible to connect more than 1 external drives to the 6128, but you'll need to make a few modifications to the the internal drive ribbon cable, and connect a few wires from external switches to the PCB inside the 6128 case, and make a cut to a trace on the PCB as well

but, with this modification installed in one of my CPC6128 computers, I've now determined that writing data to the HXC floppy emulator doesn't work (WETO or Write Error Time Out), but reading data is perfectly fine. on a another CPC6128 that I have with the AB-BA drive select modification, write operation to the HXC is perfectly fine

Have a look at the screen shot (or the ZIP file which has 2 DSK images in it) I've saved from Amstrad Technical Manual #3 (a disk magazine from the early 1990s!) - and make up your own mind about doing this modification

*the qualified longer answer, is that AMSDOS can only read and write to two floppy drives (Drive A and Drive B), but the Shugart floppy interface has the capability to use up to 4 drives (DS 0,1,2,3). The mod redirects the External Drive Select signal to the pin corresponding to DS0,1,2 (or 3) so that the internal or external drives respond as Drive A or Drive B, or not at all

« Last Edit: 16:24, 02 September 13 by archcosmo »

Offline Bryce

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Re: more than 2 drives
« Reply #2 on: 16:44, 02 September 13 »
The reason this mod doesn't work when writing (other than the fact that AMSDOS doesn't support it) is because it's still ignoring the US1 signal from the µPD765. If they had simply taken the signals from US0 (pin 28) and US1 (pin 29) and then added a 2 to 4 decoder to produce the DS0 - DS3 signals, then four drives would work as expected on the 6128 (using an OS that supported it too of course).

Bryce.

Offline archcosmo

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Re: more than 2 drives
« Reply #3 on: 00:56, 04 September 13 »
well that's good to know why my HXC doesn't write to a disk image file.. thanks! but the HXC wasn't invented when this mod was first thought up - so who could have predicted future drive emulation tech attached to the good ol 6128's  floppy interface ~20 years into the future would experience write failures....  ;) :D
I guess I'll need to dig deep and remove this mod, and install something different that leverages US0 and US1 (as well as the rest of the circuit)

but, to clarify in case I wasn't clear earlier (it was very late at night writing my first reply), there's no disk write issues for actual floppy disks, as like the ABBA modification, you can still only use two drives at once (A & B) - this mod doesn't change that limit
« Last Edit: 02:05, 04 September 13 by archcosmo »

Offline Bryce

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Re: more than 2 drives
« Reply #4 on: 11:10, 04 September 13 »
A single 74LS139 is all you would need. Connect US0 and US1 to the inputs A0a and A1a, connect /Ea to GND. The outputs /O0a, /O1a, /O2a and /O3a can be fed to the /DS0 of each drive. All drives should be set to react to /DS0.
Obviously the IC needs 5Vs and a decoupling capacitor too, and you should connect all unused inputs (A0b and A1b) to GND and the second enable /Eb should be connected to VCC via a 10K resistor.

If you want a circuit diagram let me know.

Bryce.

Offline radu14m

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Re: more than 2 drives
« Reply #5 on: 18:33, 04 September 13 »
Thanks Bryce, looks like we found a new project for the CPC :)
Or was this already done ?

Offline TFM

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Re: more than 2 drives
« Reply #6 on: 22:26, 04 September 13 »
It would be great to have a step by step documentation how to enable DS0,1,2 and 3 for a regular CPC6128 (and maybe even 6128 Plus).[nb]Drives other then A and B are supported by some CP/M patches and FutureOS.[/nb]
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Offline Bryce

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Re: more than 2 drives
« Reply #7 on: 11:47, 05 September 13 »
Here's a schematic of what needs to be done. This diagram is valid for DDI-1 / 664 / 6128 and Plus machines too. The existing tracks to pins 10 and 12 of the floppy headers (internal header and floppy socket) need to be cut also.

@Radu14m: It may have been done by some user at some time, but I don't think the information has ever been published on any CPC site?

Bryce.

« Last Edit: 11:56, 05 September 13 by Bryce »

Offline radu14m

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Re: more than 2 drives
« Reply #8 on: 17:39, 15 August 14 »
found this old thread , and want to push up the subject .
I'm tired of swapping the hxc and floppy cable on my 6128.
is it possible to have 4 drives allways connected ( weired ), but only 2 active ?
the other 2 should remain wired, but deactivated through a switch.


What you think ?


Offline TFM

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Re: more than 2 drives
« Reply #9 on: 22:46, 15 August 14 »
Well, you could use FutureOS. It supports 8 drives. 4 at the internal FDC (like the patch Bryce talked about) and four for the Vortex external FDC. So it will allow you at least to copy disc quick from drive to drive.


A patch for Amsdos is not know to me. But... you can use DDOS (not X-DDOS) from Dobbertin [size=78%]which supports 4 drives. [/size]
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Offline xesrjb

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Re: more than 2 drives
« Reply #10 on: 09:55, 18 August 14 »
But DDOS is only working under a CPC 464 !!!

xesrjb
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Offline Munchausen

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Re: more than 2 drives
« Reply #11 on: 14:39, 18 August 14 »
A version of FW3.1 with support for 4 drives would be awesome (hint hint) :D

Offline arnoldemu

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Re: more than 2 drives
« Reply #12 on: 15:04, 18 August 14 »
A version of FW3.1 with support for 4 drives would be awesome (hint hint) :D
sorry to be pedantic but you would need an updated amsdos.
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Offline TFM

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Re: more than 2 drives
« Reply #13 on: 20:53, 18 August 14 »
But DDOS is only working under a CPC 464 !!!

xesrjb


Ok, then use your X-MEM to switch OS  ;)
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Offline Munchausen

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Re: more than 2 drives
« Reply #14 on: 11:12, 19 August 14 »
sorry to be pedantic but you would need an updated amsdos.


Aha ok. Yeah I always forget where the line is drawn between DOS and the rest of the FW

Offline TFM

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Re: more than 2 drives
« Reply #15 on: 19:56, 19 August 14 »
Lower ROM  = Firmware
ROM 0 = BASIC
ROM 7 = AMSDOS


and ROMs 10,16-18 = FutureOS



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