dhc014 wrote:But it can't actually restrict the speed for these drives so there's no point, right?
The speed control for DVD-ROMs is very real: This scan is at 1x:
The following table (adapted form CDSpeed's summary) summarizes my scans of this DVD+R (Emtec 4x) with 3.88 GiB. I don't know which burner or speed was used for recording (have to ask).
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General Information
Drive: LITEON DVD-ROM LTD163
Firmware: GH4W
Disc: DVD+R (RICOHJPN R01)
Selected speed: 1 X 2 X 4 X 8 X Maximum
start 1x 1.94x 2.02x 3.58x 6.80x
end 1x 1.97x 4.54x 8.22x 15.57x
PI errors
Maximum: 78 54 47 241 576
Average: 6.19 8.87 7.08 22.14 170.12
Total: 60978 115714 88880 249583 2044447
PI failures
Maximum: 10 11 11 10 42
Average: 1.12 1.17 1.16 1.14 4.59
Total: 21224 95431 74796 69972 109728
PO failures: n/a n/a n/a n/a n/a
Jitter: n/a n/a n/a n/a n/a
Scanning statistics
Number of samples: 117966 111393 108683 110137 102996
Average scanning
interval: 1.08 ECC 1.14 ECC 1.17 ECC 1.15 ECC 1.23 ECC
Glitches removed: 4 22 2 4 93
One funny thing is that the drive revs up to full speed after completing the test and stays there until the disc is ejected.
I have some problems with totals and averages, though. For example, look at these PIF values:
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Speed 1x 2x
PIF average 1.12 1.17
total 21224 95431
The averages are about the same, but the totals differ by more than 4x ! Other ratios aren't constant either. I'd also like to know what the units are for these rates (counts per MB or second or ECC sector or sample).
G