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Re: Possible problem with accessing DVDs larger than 4GB


On Thu, February 28, 2013 21:31, Mark wrote:
>> I've been using an emulated A3000/040/SCSI CD drive config. With that,
> booting NetBSD 6.0.1 and doing
>>   # dd if=/dev/cd0c of=temp.bin bs=2048
>> fails to read the last sector of the CD; e.g. if the CD has 19057
>> sectors,
>> dd only reads 19056. (For faster testing you can add a skip= argument to
> dd, to skip most of the disc.)
> I did some more testing. At least in WinUAE (A3000, SCSI CD drive), NetBSD
> 2.1 doesn't have that problem. It reads all 19057 sectors from the disc.
> And the same with NetBSD 1.6.2 with emulated A4000 and ATAPI CD drive.
> So this issue could possibly be a regression in later NetBSD versions. Or
> it could be an emulation bug if earlier versions somehow accessed CDs
> differently.

After some more testing, it seems NetBSD 3.1 doesn't have the off-by-one
problem, but both NetBSD 4.0.1 and 5.2 do. So if this *is* actually a
NetBSD bug, the regression appeared somewhere between 3.1 and 4.0.1.

It would be great if someone could test using dd on their real Amiga and
recent NetBSD. The problem only seems to occur with CD-ROMs, not when
using dd to read the last sectors of the hard disk.

-- Mark

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