Hantek DSO2D15 sampling rate capped at 250MSa/s on memory depths above 40K

[elepo]

Hi everyone,

I finally decided to get the Hantek DSO2D15 after contemplating and researching for a while. Fortunately so far everything seems to be fine with it and I was very happy with my purchase until last night I realized a strange behavior, but I'm not sure if it's just this scope or if it's something all scopes do (since this is the first scope I'm working with).

So the problem is that the advertised sampling rate is 1GSa/s, and the memory depth 8Mpts. Now I know if I set the time base too long the scope has to reduce the sample rate in order to be able to capture the whole timespan. But by my calculations I should be able to get 1GSa/s with 8MPts memory with a time base of 500us/div, or lower. But the scope seems to be capped at 250MSa/s and never goes higher, no matter how small the time/div is, unless the 4K or 40K memory depth is selected.

I demonstrate it in this video, as you can see as I reduce the time base the sample rate keeps going up but it is capped at 250M:
https://youtu.be/JbALSoPCHHo

Only with 4K or 40K memory selected will it go to 500M or 1G sample rates. And even worse, when I activate the second channel the 250MSa/s gets halved.
So what is going on? I never saw this mentioned anywhere in reviews or specs.
Do all scopes do this? Do all Hanteks do this? Does a Rigol do this?

[elepo]

Here I made a table

[Aldo22]

This has been known for years.

-You can't sample at full speed when you are between 8Mpts-400kpts memory setting. It drops down to 250MSa/s when you set the capture memory higher than 40kpts, and it halves again to a comical 125MSa/s when you enable both channels!

Please ask your questions in the existing threads instead of starting a new thread for every question. This keeps the information together.
New Master Thread: https://www.eevblog.com/forum/testgear/hantek-dso2x1x-models-master-thread/

[elepo]

I wish besides being dead set of tearing the unit down and installing heat sinks or a fan on it, and complaining about UI lags and freezes, people also mentioned the fact that the advertised 1GSa/s and 8MPt memory is a lie. I mean it's a very important factor.
Like, the 8MPt memory was one of the main reasons I never even looked at any FNIRSI ones and now it turns out this thing also basically has a 40k memory.

I was feeling pretty great about this scope but now I don't know.

And sorry for posting here I did know about that megathread, it just didn't occur to me to post there. But for search engine results I think having a separate thread with a dedicated title is better. Since none of the AI I asked about mentioned this either, they kept saying Hantek has 8M memory.

[Aldo22]

also mentioned the fact that the advertised 1GSa/s and 8MPt memory is a lie.

It has both, just not at the same time. 

It's not great, but 40k isn't nothing, and 250MSa/s isn't nothing either.

I think that's acceptable for one of the cheapest desktop scopes.
You just have to choose between 1GSa/s or 8M.
Otherwise, send it back.