Jerry Stuckle a écrit :
> On 2/16/2013 12:33 PM, Pascal Hambourg wrote:
>>
>> 10^9 = (5 * 2)^9 = 5^9 * 2^9 = 1953125 * 512.
>> So it is possible to have a disk of 1 953 125 sectors of 512 bytes,
>> which is exactly 1 000 000 000 bytes.
>> I personnally own a disk of exactly 20 GB (20 000 000 000 bytes).
>
> No, it's not possible to have 1,953,125 sectors. Among other things,
> current disks have an even number of heads (older ones had an odd number
> because one head was use for tracking).
Isn't your information a bit outdated ?
Current disks can have an arbitrary number of heads : 1, 2, 3, 4... up
to 8 at least for 1" height disks. Check for exemple the datasheet of
the Seagate Barracuda 7200.10 series. The 80 GB models (ex: ST380215AS)
has one head, the 750 GB models (ex: ST3750640AS) has 8 heads.
Anyway the physical geometry is hidden by the embedded controller and
the "logical" geometry advertised to the host system is purely virtual
(and deprecated in favor of linear LBA addressing), so the number of
physical heads is irrelevant.
> And exactly which disk is it you have that has exactly 20,000,000,000
> bytes? Make and model?
Maxtor 2B020H1. Printed on the label is "LBA: 39062500".
Here is the output of "hdparm -IN" which confirms the size and checks
that HPA (host protected area) is disabled :
==========================
ATA device, with non-removable media
Model Number: Maxtor 2B020H1
Serial Number: B1C42JYE
Firmware Revision: WAH21PB0
Standards:
Used: ATA/ATAPI-6 T13 1410D revision 0
Supported: 6 5 4
Configuration:
Logical max current
cylinders 16383 16383
heads 16 16
sectors/track 63 63
--
CHS current addressable sectors: 16514064
LBA user addressable sectors: 39062500
Logical/Physical Sector size: 512 bytes
device size with M = 1024*1024: 19073 MBytes
device size with M = 1000*1000: 20000 MBytes (20 GB)
cache/buffer size = 2048 KBytes (type=DualPortCache)
Capabilities:
LBA, IORDY(can be disabled)
Standby timer values: spec'd by Standard, no device specific minimum
R/W multiple sector transfer: Max = 16 Current = 16
Advanced power management level: disabled
Recommended acoustic management value: 192, current value: 0
DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4
Cycle time: no flow control=120ns IORDY flow control=120ns
Commands/features:
Enabled Supported:
* SMART feature set
* Power Management feature set
* Write cache
* Look-ahead
* Host Protected Area feature set
* WRITE_VERIFY command
* WRITE_BUFFER command
* READ_BUFFER command
* NOP cmd
* DOWNLOAD_MICROCODE
Advanced Power Management feature set
SET_MAX security extension
Automatic Acoustic Management feature set
* Device Configuration Overlay feature set
HW reset results:
CBLID- above Vih
Device num = 0 determined by the jumper
Checksum: correct
max sectors = 39062500/39062500, HPA is disabled
==========================
I can understand your skeptcism, this exact GB size seems to be
uncommon. On the other disks I checked, the sector count seems to be a
multiple of 1008 = (16 heads * 63 sectors/track).
Exemples :
Maxtor 6E040T0, Seagate ST340014AS (40 GB) : 78165360 = 77545 * 16 * 63
Maxtor 6E040L0 (40 GB) : 80293248 = 79656 * 16 * 63
Western Digital WD800AAJS (80 GB) : 156301488 = 155061 * 16 * 63
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