I bought a 1660 Super AMP and it turned out to be of Hynix memory. The card gave me merely 24 MH/s on overclocking and close to 21MH/s on stock setting. I sold it

Now, I’ve been reading that at underclocking memory closer to -500 we can get a decent hashrate of 29 MH/s

Is that true and if yes then is it for all hynix cards ?