4 drives with cpc

[arnoldemu]

I know there is a modification for the cpc that will let it use 4 drives.

I also believe that the Vortex disc interface supports 4 drives.

What are the signal assignments for the drive selects for the other 2 drives?

also, if a abba drive switch was used, does this mean only drive A and B would be switched? or would it also mean C & D are switched? (I think just drive A and B because the switch works of the /drive select outputs)

[xesrjb]

I have a CPC 6128 with an internal 3,5" drive. For that a have a switch to give the A-signal to the B-Drive centronics port. So I have an A-A switch witch means internal 3,5 an external 3" drive from hitachi. At the B-Drive connector I have two drives: a 3,5" and and second 3" from hitachi. Here I altough switch the drive select that means here a B-B switch. So I have 4 drives on 2 drive selectlines!

xesrjb   

[arnoldemu]

I have a CPC 6128 with an internal 3,5" drive. For that a have a switch to give the A-signal to the B-Drive centronics port. So I have an A-A switch witch means internal 3,5 an external 3" drive from hitachi. At the B-Drive connector I have two drives: a 3,5" and and second 3" from hitachi. Here I altough switch the drive select that means here a B-B switch. So I have 4 drives on 2 drive selectlines!

xesrjb

Ok, so you have 2 switches.

First switch you are choosing drive A: internal 3.5" drive or external 3" hitachi.
Second switch you are choosing drive B: another 3.5" or 3" hitachi.

Ok, I was thinking of the other hardware modification, where the US1 from the NEC765 is connected up, and using the controller you can use 4 drives directly.

Your switch setup is a nice idea too.

[TFM]

I know there is a modification for the cpc that will let it use 4 drives.

Yes, there is at least one. However, the result is always the ability to connect drives to DS0, DS1, DS2 and DS3 of the internal FDC765. (To bother you with FutureOS stuff, there they are called A, B, C and D).

I also believe that the Vortex disc interface supports 4 drives.

Not every one. But the F1-S, F1-D, M1-S, M1-D drives have their own FDC765 in the controller, and this one supports all DS0 up to DS3 (bothering continues: under FutureOS they're called E, F, G and H). I own the F1-D (5.25" floppy station on 6128 with two drives) and it can manage four drives in total (means about 3 MB!!!)

What are the signal assignments for the drive selects for the other 2 drives?

Well, on the normal CPC drives A and B use DS0 and DS1 on the floppy connector. Floppies C and D must use DS2 and DS3 on the connector.

also, if a abba drive switch was used, does this mean only drive A and B would be switched? or would it also mean C & D are switched? (I think just drive A and B because the switch works of the /drive select outputs)

ABBA switches usually exchange the DS0 and DS1 signals.

Hope this helps you a byte

[arnoldemu]

Thank you TFM. This was exactly the info I was looking for.

I have 2 more questions:

- Do you have a schematic to show how the US1 from the NEC765 is decoded into selects for drives C and D.
- Do you know which pins on the disc connector or wires on the ribbon cable are associated with drives C and D?

I want to document this a bit more for the wiki, but also i want to support these configurations (including the one from xesrjb in arnold emulator).

[TFM]

Thank you TFM. This was exactly the info I was looking for.

Thanks, always a pleasure to help! Your kind answer is my x-mas present :-)

I have 2 more questions:

Well, I got tons of questions, but you first...

- Do you have a schematic to show how the US1 from the NEC765 is decoded into selects for drives C and D.

In the four-drive CPC? Well you add a small 2 to 4 decoder. The FDC has two signals indicating the drive select, they can be: 00, 01, 10 or 11. The CPC uses (like I guess to remember) only one of this two signals. Now the 2 to 4 decoder takes this two wires and provides signals to four wires (DS0 to DS3). It does roughly this:

00 --> 0001 = DS0
01 --> 0010 = DS1
10 --> 0100 = DS2
11 --> 1000 = DS3

For schematics I have to check out some of my paper sources at x-mas...

- Do you know which pins on the disc connector or wires on the ribbon cable are associated with drives C and D?

The off-the-shelves CPC has only a connection for DS1. That allows to use a B-drive. The DS0, DS2 and DS3 signals / pins are not connected.

DS-0 Pin 10 (not connected)
DS-1 Pin 12 (B-drive)
DS-2 Pin 14 (not connected)
DS-3 Pin 6 (not connected)

In principle (diregarding DS signals) the CPC drive B port is compatible to the shugart standart.

I want to document this a bit more for the wiki, but also i want to support these configurations (including the one from xesrjb in arnold emulator).

Sounds great!!! 

[arnoldemu]

Thankyou again.

For schematics I have to check out some of my paper sources at x-mas...

I would appreciate that if you have the time to do so.

Well, I got tons of questions, but you first...

Perhaps I could answer some?