From: | Craig_Daines |
Date: | 1 Jun 2001 at 01:09:30 |
Subject: | Re: Max transfer Rates (reply) |
--- In amigactive@y..., Elizabeth Green <nine-f@c...> wrote:
> Hello Neil
>
> On 31-May-01, you wrote:
>
> > Kai Rose said,
>
> >>> What's the Max Transfer Rate supposed to be?
>
> >>Don't fool around with it, leave it as default!
>
> > The default is WRONG. You *will* corrupt data by using the
> > default value on many IDE drives.
>
> So, my default figure is wrong. I will change to what you
> recommend -but do I then have to change any other values? eg Mask.
>
> The drive when corrupt won't boot - it spins up, gets about half
> way through start-up, and then 'chatters'
> I suppose this is the best description, and it will not get any
> further. I can access the rest of the partitions if I got to
> early boot options and disable that particular partition. It's
> done it twice now. The drive however reports no bad blocks or
> errors from HDToolBox. Quarterback won't work on a partition it
> can't see.
Hello Liz
I detail below settings for Mask & Maxtransfer:-
Explanation of Mask and Settings:
The DMAMask indicates which memory area the host adaptor can access
with DMA. High speed devices like disk controllers can read and write
data from memory without any CPU load. This is refered to as Dynamic
Memory Access or DMA. Unfortunately, some devices can only access
part of the memory. Any Zorro II IDE controller board, for instance,
can only access the lower 16MB of memory (since Z2 uses a 16 bit bus).
The corresponding value for Mask is 0xfffffc.
Zorro III IDE/SCSI hostadaptors can access all memory, so for those
use 0xfffffffc. *Double check* what kind of board is used, since the
if the Mask is set wrong it can in some instances result in serious
problems with the disk.
Mask is also used to control the alignment of any buffers used to
access the device. In most cases, alignment to longword is
recommended, but even those will perform a lot better with aligned
memory. Longword alignment is selected by ending the mask setting
with a 'c'.
For most boards, the best Mask settings are:-
Zorro II Board: use 0xfffffc.
Zorro III Board: use 0xfffffffc.
If you experience problems with the Mask, you can try other values.
Explanation of MaxTransfer & Settings:-
This setting indicates how much data can be send to the device in one
go. Some drives *cannot* handle large blocks of data. By specifying
the maximum the device can handle, problems are prevented. Most scsi
devices can handle a MaxTransfer of 0xfffe00, which is 16 megabytes.
For some IDE devices 0x1fe00 (130k) is necessary. If files greater
than 64K get corrupted then reduce it to: 0xfe00.
The Maxtransfer must be divisible by the drive sector size
(block size), which is usually 512 due to a bug in the Workbench
format code. This is done by ending the value with 'e00'. For
example, instead of 0xffffff, use 0xfffe00.
Kind regards,
Craig Daines
Technical Editor For 'The Crypt'
http://www.thecrypt.org
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