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PC XT with 2 RLL hard drive controller cards

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NicolasF

Experienced Member
Joined
Jun 28, 2006
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255
Location
Argentina
Hi,

Is it possible to install 2 RLL hard drive controllers in the same PC? I know one controller can handle 2 drives, but I'm curious to know if I can install one hard drive in each controller.
It seems like it might be posible. I've read someone used 2 controllers, one was MFM and the other was RLL.

Thanks!
 
I would suspect that unless you can configure one controller as primary and another as secondary they would fight over the same interrupts and addresses.
 
PC and XT-class universe:

By default, MFM/RLL controllers use the same 'resources' (base address for the BIOS ROM, I/O address, etc.). See the top half of [here]. The expected result is a 'resource conflict'.

So the second controller would need:
- To use different 'resources' to the first, plus
- The BIOS ROM on the second controller would need to support those 'resources'. (Or a suitable driver used instead.)
 
Ok, so it's not going to work. I will have to install both hard drives with the same controller.
 
I'm going to guess here... Hardcard (which could do secondary), and that would be what RLL? And an MFM controller with 10-20mb hard drive. Would make sense on the brag lol.
 
Isn't the answer simply: yes, if one of the controllers supports it..?

If you find a controller that allows changing the BIOS and I/O addresses as well as the IRQ, it will work. 16-bit controller cards being able to do that are plenty. Not sure about 8-bit cards, however. But I don't see why such shouldn't exist.
 
...and the BIOS extension would need to be able to "hook" Int 13h services correctly and recognize the added unit number. That's a pretty tall order. I suppose you could concoct a loadable device driver in place of a BIOS extension, but the whole thing would not be simple. I can recall doing something similar when using one of the 1224 cylinder ST506 hard drives--most controller BIOSes would only handle cylinders to 1023; to access the other 200, I had to write my own driver.
 
I have an ST11R controller and I found the manual online. It has jumpers that allows you to change the BIOS memory location. So it might be posible to use 2 controllers. If I use 2 controllers I dont have to move the hard drive that I already have installed. But if I connect both hard drives with the same controller I'll have to put them one on top of the other and I'll have to find something to cover the hole so yeah... I dont know. All this assuming the hard drive works because I bought it as is. But finding an ST-238R for sale here and cheap is extremely rare so I couldn't let it go. I looked for them on ebay in the US and they are quite expensive too, like 100USD to 200USD which is a lot of money in the US right? We'll see maybe I just bought a cool looking brick!
 
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