Amiga drive to a PC drive for WinUAE

[Ed Cruse]

This probably sounds dumb, just format it with Windows, but it's not really that easy. When I was testing 0x76 partitions I used a drive that had been set up for a real Amiga with an RDB. No matter what I did I couldn't get WinUAE and HDToolBox from thinking there was a RDB on the drive. I did a full PC format making it active and wrote a large file to the drive, Defrag confirmed the file started at the beginning. The problem is WinUAE still saw the drive as an Amiga drive and listed it as RDB, even though it was formated as NTFS. I believe I could have installed Windows on the drive, booted to it, and it would still have been listed as a RDB drive by WinUAE, I didn't try so I don't know for sure. This would have allowed me to install the drive and write to it with HDToolBox, killing Windows.

I did finally kill the RDB by tricking the Amiga into formating cylinders 0 and 1, but it was a pain. A better way is to use the 0x76 partition idea. Even if you want to use the whole drive for the Amiga, don't use cylinders 0 and 1 of the drive. Use Windows to partition the whole drive, edit the partition table and make the partition a 0x76 and then change the first cylinder from 0 to 2. That way the RDB will actually be in cylinders 2 and 3 even though to the Amiga it's in 0 and 1. When it's time to convert the drive back to a PC drive, simply remove the 0x76 partition and format. WinUAE won't see the 0x76 partition anymore and it won't see any RDB in the first two cylinders of the drive. Anything left of the RDB will be in cylinders 2 and 3 which WinUAE doesn't care about. I actually tried this and it did work.

Now this won't work if you want to set up a drive for a real Amiga, this only works for WinUAE.

If anybody has a better idea I'm all ears.

[thomas]

http://thomas-rapp.homepage.t-online...ds/killrdb.lha

HDInstTool has such an option, too IIRC.

What kind of controller do you have in your real Amiga ? Usually the RDSK block is in block 0 of the HDD and is overwritten when writing a PC partition table to the drive.

However, the Amiga allows to have the RDSK block in anywhere in block 0 .. 16. So your controller or your partitioning software probably moved it some blocks behind so that it is not overwritten by the PC software.

IMHO you should not use a complete HDD nor a x76 partition for WinUAE if you don't want to share data with a real Amiga or Amithlon. That's what these types of disks are meant for. If you want to experiment with "real" harddrives in AmigaOS you can as well use a HDF or a VHD in RDB mode. From the Amiga side it's exactly the same and from the PC side it's much easier to handle. You can simply delete and recreate the file if you screwed it up.

[Ed Cruse]

Originally Posted by thomas

http://thomas-rapp.homepage.t-online...ds/killrdb.lha

HDInstTool has such an option, too IIRC.

What kind of controller do you have in your real Amiga ? Usually the RDSK block is in block 0 of the HDD and is overwritten when writing a PC partition table to the drive.

However, the Amiga allows to have the RDSK block in anywhere in block 0 .. 16. So your controller or your partitioning software probably moved it some blocks behind so that it is not overwritten by the PC software.

IMHO you should not use a complete HDD nor a x76 partition for WinUAE if you don't want to share data with a real Amiga or Amithlon. That's what these types of disks are meant for. If you want to experiment with "real" harddrives in AmigaOS you can as well use a HDF or a VHD in RDB mode. From the Amiga side it's exactly the same and from the PC side it's much easier to handle. You can simply delete and recreate the file if you screwed it up.

Actually I originally created the Amiga HD by using WinUAE and 3.9's HDToolBox, so where ever HDToolBox puts it. Isn't the first possile block on the harddrive for the RDB block #2? The first two block are reserved, at least that's the default, which may explain why the PC format didn't write over it. I know writing an RDB doesn't write over the first block of the drive because Windows still sees the same partition info that was present before the RDB was written. Generally it's a good idea to delete the PC partitions before setting up the drive for an Amiga so the drive won't show up in Windows.

As far as using drives directly with the Amiga, I don't. I use RDB hardfiles, I was just experimenting to see how fast they are compared to hardfiles. The speed of directly accessing the drive is actually faster, less overhead-no Windows cache, but the Windows cache more then makes up for that most of the time. It's difficult to beat ram for speed.

Do you know if there's any reason why reserving blocks at the beginning can't be set to 0? That might be an easy way to solve converting drives from PC to Amiga to PC to Amiga and so on.

[Toni Wilen]

Reserved blocks are blocks at the start of _a partition_. Nothing to do with partition table blocks.

[Ed Cruse]

Originally Posted by Toni Wilen

Reserved blocks are blocks at the start of _a partition_. Nothing to do with partition table blocks.

That makes sense because of where the reserved block setting is located in HDToolBox.

When the RDB is written does it write the RDB starting at drive sector #0?

The reason I'm asking is I experimented again and I got totally different results, which is normal when I don't know what I'm doing. I made a PC drive, then wrote an RDB to it, and then looked at the pc partition table and it was totally zeroed out, I even had to initialize the drive before I could PC partition it. I had no problems with converting back and forth between PC and Amiga drives and leaving any trace of the prevous setup. I sure had a difficult time getting rid of all traces of the RDB when I used the same drive for doing the 0x76 testing though. I don't know what I did different that first time. Maybe I did something wrong this time, who knows. One thing I did learn, when not using Windows to make changes to a drive, usually a reboot is required before the changes take effect, maybe that's where I went astray.

[thomas]

when not using Windows to make changes to a drive, usually a reboot is required before the changes take effect

Connect the drive to USB, then you can simply unplug and replug it to apply the changes.