*Can the ADFS on a RiscPC support two Disc Drives?*

My Risc PC has two IDE Drives connected via a Blitz Card, I would like to add a second drive to the ADFS which at present has one drive connected, the Boot drive. As I have a second slice, Network card,USB Card,Floppy Drive and CD drive I am unable to see if the ribbon cable has a connector half way along its length. I do not want to have to remove all the bits and pieces and find that it cannot support the second drive, also is there an upper limit to the disc size? The OS is 4.02. Can I make it a bootable drive when I format it even though it will not take the place of the existing Boot Drive, I would if possible back up the Boot files on to it just encase the original becomes faulty.
In a previous post I thought the original drive was becoming fault, but, fingers crossed, the noise which I thought was ominous seems to have ceased!

I seem to have missed a “W” out of the title!

Fixed it for you (I hope)

The Risc PC does support two drives, but the standard cable has only two connectors, not the three needed.

Upper limit on disc drive size is 256 GiB. Or, more precisely, you can only use the first 256 GiB of any disc drive (i.e larger drives, if compatible, can be “downformatted”). Only 512 bytes/sector are supported, so no new-fangled 4K sector stuff.

However, a word of warning – ADFS is quite picky wrt drive compatibility. There is a longish thread on Stardot forum where a patched ADFS was provided by Jon Abbott which improved compatibility somewhat.

I think Steffan is referring to the “Disc Error 20/21/23 and SATA→IDE support” thread

If you get Disc Error 20, you can either run the RiscPC live patcher in that post during boot or use it to create pre-patched ADFS Module to load during boot.

If you get Disc Error 20, you can either run the RiscPC live patcher in that post during boot or use it to create pre-patched ADFS Module to load during boot.

There’s also the third option of installing ROOL’s ROMpatch for the issue (although it does require a bit of effort to dig it out of the hard disc image)

Assuming my Disc drive is compatible could an extension be use to give a third plug in off the ribbon cable or does the CD Drive take the second connection?

As I understand it, the blitz can support four devices. You say it’s currently got two hard drives connected, but you also have a CD drive. If that isn’t connected to the blitz it will be the second device on the motherboard.
The motherboard will support maximum of two devices. If the CD is the second motherboard device, and you just want the second drive set up as a replica of the first then you could temporarily connect it instead of the CD drive to set it up. There would be no issue having both set as bootable.

AFAIK in IDE bus it’s the slower device that dictates speed, so in PC world the IDE CD/DVD drives were installed in a channel, and hard disks on the other to increase performance.

AFAIK in IDE bus it’s the slower device that dictates speed, so in PC world the IDE CD/DVD drives were installed in a channel, and hard disks on the other to increase performance.

On the Risc PC, everything is operating in PIO mode 0, so everything operates at the same (the slowest) speed anyway.

Yes, but Blitz card was supposed to operate in DMA mode when installed in a particular slot position in RPC (I seem to remember that in my podule riser card(?) only in the upper slot DMA is possible), so when mixing CD/DVD drives and HDDs, it’s better to use one channel for CD and another for HDD. In the Motherboard IDE of RPC there is only one channel, so yes, it’s slow.

Yes, but Blitz card was supposed to operate in DMA mode when installed in a particular slot position in RPC (I seem to remember that in my podule riser card(?) only in the upper slot DMA is possible), so when mixing CD/DVD drives and HDDs, it’s better to use one channel for CD and another for HDD. In the Motherboard IDE of RPC there is only one channel, so yes, it’s slow.

The DMA capabilities of Blitz relate to the podule side of things (32bit DEBI instead of 16bit non-DMA), not to the devices operation.

I am not sure which PIO mode Blitz uses, but it does not use UDMA. RISC OS has no capability of parallel and non-blocking I/O which could in theory profit from putting one device on the first channel and the other on the second channel. And DEBI with its theoretical bandwidth limit of 16 MiB/s (which practially is around 6-8 MiB/s depending on the amount of software trickery you employ) would be outrunned by even the lowest common UDMA denominator UDMA33.

So whatever way you look at it, I would be very surprised if it matters where you put the devices on the Blitz.

Anyway, this discussion should surely not happen in “Announcements”.