okay good. I take it the fact you can tell the DMA modes a sign that you are using the native microsoft AHCI driver? With Intel RST, it only shows the Intel ICHx AHCI Controller here.
Have you confirmed your results with something like crystaldiskmark, or AS SSD benchmark?
Generally with DMA modes falling back, to eventually PIO modes, it's because of errors. so things like drivers, physical cables, the drive itself needs to be checked. Have you taken any steps to confirm the drive is operating at optimum itself (e.g. checking it whilst it's hooked into another computer - partition alignment, confirming TRIMd (eg. try manually via toolbox), check the SMART values as reported by the toolbox).
I've used crystaldiskmark to confirm the slower speed as well.
But here's the thing. Regardless of what port the SSD is on and what
mode it's in, one thing always remains the same. And that is when I
overclock my processor, the speeds go up to what is considered
normal for an SSD.
I was getting read speeds of 236mbs in pio mode 4 when overclocked.
I changed ports and in Udma-6, I get 236mbs overclocked.
I go with stock settings and I get 185mbs reads whether it's pio 4 or
udma-6 as well. It literally makes no sense to me because HD tune
or crystalmark are hardly using any processor power when running.
Trim is working, alignment is fine. All confirmed through Intels SSD
tell me when did you first notice this? is it a completely new build? has it been running fine for ages and the issue just popped up one day?
I just removed RST from a current machine i have on the bench (except its a 40GB X25-V) and I can see youre using the default MS AHCI driver as it reports what you are describing (except mine is in UDMA-6). The thing is, PIO mode 4 (the maximum for PIO) is so much slower than (your reported 180~MBs) that it's not funny, so that definitely doesnt make sense.
regarding overclocking, i would say something is being pushed past a specified frequency (not cpu - think of a more along the lines of a bus the SSD uses in the PCH?)
It would be good if you could confirm the SSD on another machine (attached as non-boot device such that it doesn't boot from the SSD). all indications are that if you overclock and it increases the read speeds, that the ssd is fine and you need to look more closely at the rest of the system. so unless this is easy to do, i wouldn't worry too much.
Have you considered some pretty drastic testing?
Here is what I would do:
- Reset CMOS on your motherboard. Power off at the wall and close the CMOS jumper for a minute. Reset to optimised defaults, configure your normal settings (e.g Intel PCH SATA mode to AHCI, etc.) - personally, i disconnect my drives during this stage and connect up after complete
- Swap out the SATA cable if you haven't already
- Test again. If the same, continue:
- Use the back up feature of windows 7 to image your SSD. I have used this and have to say it is excellent - restored perfectly, partition aligned, etc.
You could backup your SSD drive via the imaging utility to an external drive. Nuke your SSD, and reinstall win7. you need only install some basic drivers like chipset, etc. to re-test the storage performance. (personally, after installing chipset & NIC drivers, i run windows update then proceed with things like RST/storage, video drivers etc.)
- if same results, you know it's not your filesystem/OS/drivers. You can then nuke the SSD agian, use the restore feature to write the image back to the SSD. you will be back where you started, but will have done a pretty valuable test IMO.
my logic is pretty out of whack as i've had an inner ear issue, leaving me dizzy as hell for the last 48 hours, so admittedly even i've gone arseabout in steps i would have done.