X25-m ridicolous speed at my laptop, something wrong?

[Susan82]

I just plugged in a new x25-m 80gb to my laptop, but knowing that my laptop (Dell XPS M1330) is only SATA1 (so limited to 1.5gbs) (which I've had confirmed in many threads) I knew I wouldn't get the full speed (tomshardware charts maxs out at 200MB/s) but I needed something to spend money on so I bought it anyway.

So I tried in SiSoft Sandra now and the results I get back is an average of 243MB/s, clearly way beyond SATA1 limitation. (but also suspiciously way beyond Tomshardware's review score)..

could it be the numbers are just messing with me?

 

[cjl]

Download HDtune and see what it says.

 

[ShadowFlash]

Was that Sandra's drive index or the individual broken down scores scrolled too at the bottom ? Sandra's drive index is kinda bunk and should be ignored, but the individual scores are usually OK.

 

[Susan82]

Ah, HDtune shows a much more realistic graph, where it constantly platos on 182MB/s, could that be the SATA1 limitation?
I've heard that sata 1.5gb/s is about 175MB/s BUT that it never goes up to those speeds because much of the bandwithd is taken up by protocoll or something.

 

[MRFS]

No. The SATA protocol is a serial protocol,
like the old RS-232 modem protocols.

For each byte transmitted, there are 8 data bits
plus 1 start bit and 1 stop bit, for a total of 10 bits per byte.

Thus, a SATA channel that oscillates at 1.5 GHz
can move 1.5 GHz/10 = 150 Megabytes per second.

JUST DIVIDE BY TEN.

Now, if your SSD cable is configured to run at 150 MB/second,
that is an absolute ceiling or limitation on the speed of that cable.

I suspect that something else is happening:
such as a bug in the measurement software you are using,
or your I/O controller has actually detected a SATA/3G device
and has upgraded the channel speed to 300 MB/second
(3Gbps/10).

The difference between 300 and 175 can be explained by
SSD device overhead e.g. in the controller logic inside that SSD
handling the "test" given to it by your measurement software.


MRFS

 

[Ignatowski]

the m1330 supports sata2.

 

[Susan82]

No. The SATA protocol is a serial protocol,
like the old RS-232 modem protocols.

For each byte transmitted, there are 8 data bits
plus 1 start bit and 1 stop bit, for a total of 10 bits per byte.

Thus, a SATA channel that oscillates at 1.5 GHz
can move 1.5 GHz/10 = 150 Megabytes per second.

JUST DIVIDE BY TEN.

Now, if your SSD cable is configured to run at 150 MB/second,
that is an absolute ceiling or limitation on the speed of that cable.

I suspect that something else is happening:
such as a bug in the measurement software you are using,
or your I/O controller has actually detected a SATA/3G device
and has upgraded the channel speed to 300 MB/second
(3Gbps/10).

The difference between 300 and 175 can be explained by
SSD device overhead e.g. in the controller logic inside that SSD
handling the "test" given to it by your measurement software.


MRFS

Thanks for that detailed description.

the m1330 supports sata2.

I read on another forum: (topic was if m1330 had sata2)
"Let's be clear.

ICH8 provides SATA-II support, but it is not a SATA-II chipset in itself.

You won't get the speed benefits of SATA-II, as I've discovered upon installing a faster than SATA-I SSD
All it means is that SATA-II HDDs will work with it...

Feel free to benchmark with ATTO (download here) if you don't believe me.
From my research so far, it would appear there is NOT a single SATA-II mobile chipset out there "

--
In summary I guess the data suggest SATA2 :S I just tried at work (quad-core stationary computer that I assume is SATA2) where HDtune keept platoing at 193 (instead of 185 which I get on my laptop) so that seems to suggest that the reason my scores are platoing in HDtune can be something else than a SATA1 limitation.

 

[cjl]

If you're getting 185, then the other person is wrong. SATA as originally specified could not provide that speed, so you clearly do have full SATA 3Gbps support.

 

[Susan82]

If you're getting 185, then the other person is wrong. SATA as originally specified could not provide that speed, so you clearly do have full SATA 3Gbps support.

Woohoo

Btw here's my chart:

I'm kind of curious why it's platoing (now that I know it's not SATA1 limitation), BUT 183 is pretty damn fast enough so I'm still happy regardless
Tomshardware seems to get like 200 MB/s constantly from this drive.

 

[chazmataz]

I have read that some c-state support in the BIOS for some power-saving modes
sharply reduces maximum transfer rates for SSDs.

I believe I read it here at Tom's Hardware. See

http://www.tomshardware.com/reviews/ssd-hdd-power,2170-4.html

Yup - advanced power-saving features cut maximum speed to ~185MB/sec