I had exactly the same issue on my Sapphire RX580 Nitro+ 8GB cards on the latest Ethos. I expected the stock BIOS to achieve 24-25MH/s, but instead got only 18MH/s on the quiet BIOS or 20MH/s on the Boost BIOS (via card BIOS switch). After some investigation I found that (using the Boost BIOS) lowering the core and mem clocks to spec rates (1257Mhz core, 2000MHz mem) actually improved it slightly to 21MH/s, but no where near to 25MH/s. I then did a VBIOS mod copying the 1750 memory timing strap to 2000 and 2250 entries and now I can run the cards at the advertised boost rate (as sold by Sapphire) of 1340Mhz core and 2100MHz mem with slightly over 25MH/s per card. Note that I switched from the default ethminer to claymore to gain a few percent. Feel free to contact me if you want to try to replicate these steps.
considering
https://www.techpowerup.com/gpudb/2224/geforce-gt-750m
your gpu has 2gb ram. You need at least 3gb.
You can reassure yourself running
$ clinfo
or
$ ethminer -G --list-devices
Otherwise you can see your real hashrate by using
ethminer --farm-recheck 200 -G -S eu1.ethermine.org:4444 -FS eu2.ethermine.org:4444 -O 0xYOURWALLET.YOURRIG
Hope this helped
EDIT:
to make it short, no it is not possible to mine with this graphicunit.
During an earlier stage it was possible because the files used in the vram were smaller.
Listing OpenCL devices.
FORMAT: [deviceID] deviceName
[0] Tonga
CL_DEVICE_TYPE: GPU
CL_DEVICE_GLOBAL_MEM_SIZE: 4294967296
CL_DEVICE_MAX_MEM_ALLOC_SIZE: 4026531840
CL_DEVICE_MAX_WORK_GROUP_SIZE: 256
the marked memory should be >=2gb.
CL_DEVICE_GLOBAL_MEM_SIZE
is not the memory which belongs to the gpu as you can read here:
https://software.intel.com/sites/landingpage/opencl/optimization-guide/Global_Memory_Size.htm
EDIT2:
I'm not really deep into parallel programming and never tried to make an inbuild gpu like yours running for mining. So be aware this is more guessing and trying to make common sense :)
The ram which is most important for mining is the gddr which is explicitly on the card if you look on a dedicated card.like rx470/480 rx570/580 etc...
https://en.wikipedia.org/wiki/GDDR_SDRAM
https://en.wikipedia.org/wiki/GDDR5_SDRAM
maybe the last one is helpful.
The amount of memory which your laptop have on its SO-DIMMs is not quite relevant beside of running the OS and some other applications because thats the memory their algorithm work with.
https://en.wikipedia.org/wiki/Random-access_memory
It is possible to allocate some of your system memory to your graphiccards memory, nevertheless I've never seen any kind of params you can use for any miner. Maybe the algorithm would not perform well enough or there is some other kind of issue I cannot think of right now for not using ddr from regular dimms.
Did you actually try that command I mentioned before, except for replacing 0xYOURWALLET.YOURRIG with your data?
Get yourself a wallet and try it, I'm using the one from the main page:
https://ethereum.org/
Or any other wallet, just to check if its running.
This is in some way over information, but still good to know ;)
Try that command and post it please.
Cheers
Best Answer
That's pretty much impossible to answer. A driver is a hardware's soul, it has full control over the hardware and what it will do, and how it will do it.
A few things that could influence it:
All in all it's pretty much impossible to answer it properly without a deep understanding of both the hardware and the driver code itself too. Even if the driver works perfectly, it always comes down to balancing various things to achieve an optimal performance on some baseline benchmark, which may or may not lie close to the requirements of ethash.