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Why isn't the read speed across some USB keys constant?
Why isn't the read speed across some USB keys at least approximately
constant? I have am running Windows XP Professional with Service Pack 1 on a 2.4GHz Pentium 4 based system with 512MB of main memory. I have tried both HD Tune 2.52 tab Benchmark and HD Tach version 3.0.1.0 Long bench (32mb zones) I get the about the same results for a particular USB Flash key with both programs. I noticed that my Kingston Data Traveler Secure DTS/4GB ran about 2MB/second slower after about 3GB. I then tested a SanDisk cruzer micro 4.0 GB BH6061GB SDCZ6-4096 and noticed a similar drop, but starting at about 2GB. I then tested an OCZ Rally 2GB (model number not available) and it dropped at about 1GB (out of 2GB) That's strange: .. some slow at 2GB, some at 1GB, so not an obvious USB interface problem on the system. .. some slow 1/2 way through, but some 3/4. Maybe not a generic flash memory issue, but something to do with the exact chip layout. However, I tried my second SanDisk cruzer micro 4.0 GB BH6061GB SDCZ-4096 It showed a flat read speed over the entire 4GB. I even switched the SanDisk cruzer micro devices between two USB jacks on the system and confirmed that the device itself had the problem, not the slot. None of the devices are brand new, but I have only used them for a few benchmarks and copy operations of either a few large files or tree copy operations. The trees had about 10000 to 20000 files and totaled about 1/2 of the USB key size in each case. I didn't do any life tests, like writing the same block multiple times. I assume that I am seeing a failure mode, but how can I isolate it so that I can get warranty replacement units from the vendors? |
#2
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Why isn't the read speed across some USB keys constant?
There was an article on ExtremeTech's website discussing which USB keys
will work with VISTA's ReadyBoost feature and it explains why not all USB thumb drives are create equal, check it out: http://www.extremetech.com/article2/...2017818,00.asp Key phrase from the article is: "Another issue is the way flash memory is laid out. Some larger capacity devices that can be had fairly cheaply get their high transfer rates by using a small amount of very fast flash memory, with the bulk being slower memory. In effect, the fast flash is acting as a buffer for the slower flash." -- Nik Simpson |
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