[Solved] Decrease in throughput after overclock

[Vishnu Rao]

I have a USB HDD connected to the USB3.0 port of my RT-AC68U. I am hitting about 12 MB/s write and 22 MB/s read. I read somewhere (can't recall, but likely this forum) that an overclock will increase the throughput and that the RT-AC68U is limited by its SoC and 256 MB RAM.

I used the overclock instructions provided here: https://github.com/kvic-z/goodies-asuswrt/wiki/Overclock-Asuswrt-Merlin-on-v378.56-and-beyond

I first overclocked the RAM to 800. Then I overclocked the SoC. At 800,800 (Soc, RAM) I am able to hit the numbers quoted above. However any overclocks on the SoC, decrease the throughput to about 5 MB/s write and 7-8 MB/s read. This is contrary to expectation. I have tried SoC clocks of 1000, 1200. 1400 definitely is not stable.

Note: I confirmed SoC overclock by cat /proc/cpuinfo. Shows twice the clock freq. So I think the overclock is working. I see increased temperatures as well.

Any ideas why the throughput will decrease when I overclock?

Thanks in advance.

 

[Vexira]

Over heating and thermal throttling.

 

[Grisu]

I think changing USB to 2.0 on admin page and you will see better speeds with OC. The problem is not OC or overheating as long as you are below 80°C but bad shielding of USB3.0 port interfering with Wifi 2,4G.
Did you test with ethernet-LAN connection or Wifi? Use a cable for testing!

Maybe you really have a thermal problem, but then its bad connection between chips and heatsink (common problem on 68U), correct it and you get under 70°C without any fan.
https://www.snbforums.com/threads/high-temp-378-56.27731/page-2#post-212548

 

[john9527]

On the newer routers attempting to overclock via nvram will actually cripple the router by underclocking. It used to be on AC87 and above, but it may have made it into the later AC68 builds.

 

[Grisu]

On the newer routers attempting to overclock via nvram will actually cripple the router by underclocking. It used to be on AC87 and above, but it may have made it into the later AC68 builds.

but then he would not see his changes in bogomips (double value of clock-MHz), they would go down too as far as I read in some postings here.

 

[Dave Parker]

If you need a little extra cooling for the 68U overclocked you might try this

https://www.amazon.com/dp/B0721SYYTF/?tag=snbforums-20

Works on the 86U also.

 

[Vishnu Rao]

Thank you all for the responses.

I am keeping an eye on the temperature. I don't think I am hitting thermal throttle. SoC/ CPU is not going above 80C at this time. I can add some cooling via a USB powered FAN (but not like the one that was listed above).

For the moment, its primarily an exercise to figure out how to improve the throughput and then figure out a long term strategy to keep it as a permanent change.

I will try switching to USB 2.0 for the USB mode.

I have tried on both cable and wifi. Same throughput on both wifi and cable. For wifi I was using a brand new USB-AC68 adapter. I bought the adapter, primarily to increase the throughput and reduce time copying to the HDD connected to the router.

I don't know how the USB interference due to 2.4GHz happens. Please note all wifi traffic is going through the 5GHz bands.

Anyone know if the filesystem on the HDD makes any difference? I am using EXT3 on the HDD. I did try connecting a 240GB SSD, formatted as NTFS, to the same USB 3.0 port. I believe the throughput was the same.

 

[Grisu]

If you dont use (or disabled) 2.4G than it wont interfere or disturb your connections. Problem that frequenzies used for USB3.0 are in the range of 2.4G and antennas too near the ports and cables often bad shielded.
Anyway some have much more troubles with 3.0. File system can make a huge difference.
From my experience this NAS-implementation never worked satisfying on Asus routers (had some DSL, RT68 and 86).

Another problem many sticks die if permanently connected as they get too warm for long time run dirctly connected to an port on the router.
And software cannot handle too many files on a disk, should be better if you have only large videos and pictures.

Thats why I used it only for DownloadMaster (no prob when file system gets corrupted, just reset/reformat and start downloads again) and even this has been broken with last firmwares when DM disappeared after installing!

 

[Vishnu Rao]

@ Grisu Thanks again explaining how the 2.4GHz interference works. Unfortunately I do use the 2.4GHz band for some of the wifi switches, raspberry pi running pi-hole etc. But most of my data transfer devices are all on the 5 Ghz band.

I switched to USB 2.0 mode. And then tried the overclock to 1200, 800. The throughput did seem to increase by about 2 MBps, but then the variance in the measurements also increased. I use NAStester. While the average increased, by about 2 MBps, the variance also increased. So some measurements were higher and some significantly lower. I will keep testing and trying.

After the overclock the idle time temperature does not seem to be very concerning. with an indoor temperature of 70F, the SoC is measuring about 75-76 C. With a heavy workload like file transfer or rsync from one USB HDD to the second USB HDD, the temperature hits 80-81C. Attachment shows increase in temperature when an rsync operation was run, shows 78-79C max. Certainly overclock is in place. But last night the temperature was more like 80-81C. Maybe cooler ambient temperature in the morning, since the router sits close to a exterior wall.

For the moment, I will stick to USB 2.0 and the overclock. But will need to monitor when summer arrives, since my indoor temperature goes higher to 77-78 F (I prefer warmer temperatures). Thanks for your help.

 

[Vishnu Rao]

Another update. Tested with a USB HDD formatted as NTFS. The write speeds have improved significantly. I am hitting about 20MBps averaged across 10 iterations. Interestingly no change in the read speeds.

I guess, I will have to reformat both my 2TB drives to NTFS then. This is hard since I have ~ 1.2 TB of memories stored in the drives. But since I am mimicking a RAID1.

So in summary, the keys to improved NAS throughput were use of NTFS format, switch to USB 2.0 and the overclock.

 

[L&LD]

Another update. Tested with a USB HDD formatted as NTFS. The write speeds have improved significantly. I am hitting about 20MBps averaged across 10 iterations. Interestingly no change in the read speeds.

I guess, I will have to reformat both my 2TB drives to NTFS then. This is hard since I have ~ 1.2 TB of memories stored in the drives. But since I am mimicking a RAID1.

So in summary, the keys to improved NAS throughput were use of NTFS format, switch to USB 2.0 and the overclock.

Just for clarification, you did not improve NAS throughput, you improved USB drive throughput.

I would be surprised if you did not achieve similar speeds on NTFS without overclocking.

 

[Grisu]

After the overclock the idle time temperature does not seem to be very concerning. with an indoor temperature of 70F, the SoC is measuring about 75-76 C. With a heavy workload like file transfer or rsync from one USB HDD to the second USB HDD, the temperature hits 80-81C. Attachment shows increase in temperature when an rsync operation was run, shows 78-79C max. Certainly overclock is in place. But last night the temperature was more like 80-81C. Maybe cooler ambient temperature in the morning, since the router sits close to a exterior wall.

I would open the case (2 screws under the backside-sticker, remove front housing with old credit card) and reapply heatsink and paste or pads, if done correct you will end with <70°C CPU-temp without additional fans.

 

[Vishnu Rao]

Just for clarification, you did not improve NAS throughput, you improved USB drive throughput.

I would be surprised if you did not achieve similar speeds on NTFS without overclocking.

I tested with the original SoC settings. It was about 1-2 MBps lower. I guess switching the USB mode and use of NTFS made the biggest difference. Overclock is more like a 1-2 MBps contributor. I will take everybit I can, since this is my only NAS set up.

Thanks for the pointer. If I ever see unmanageable SoC temps in the summer, I certainly know I can underclock and yet get acceptable R/W speeds.

 

[Vishnu Rao]

I would open the case (2 screws under the backside-sticker, remove front housing with old credit card) and reapply heatsink and paste or pads, if done correct you will end with <70°C CPU-temp without additional fans.

I am not too concerned about temperatures. Silicon temperatures of upto 100C should not be a problem. Atleast thats been my experience from working on storage devices.

 

[Grisu]

I am not too concerned about temperatures. Silicon temperatures of upto 100C should not be a problem. Atleast thats been my experience from working on storage devices.

Can only tell you there are many users here reporting dead sticks even after short time.

 

[RMerlin]

Can only tell you there are many users here reporting dead sticks even after short time.

A lot of garbage is being sold these days, even from well known brands. I've had more than my share of USB thumbdrives dying an early death even when getting used only once in a whole.