Originally Posted by Aontaigh
These are my default RTL/IOLs:
JP posted this above.
RTLs are measured during post, so the extent they can be lowered, and still pass POST, will depend on the margins in trace length/path and the ram ICs layout. If you manually change these to bad values you will have to clrcmos to get back into bios unless your board has a safeboot function or MemOkay reset. (Q-codes like 49, 55 will be common on most boards when these cannot train).
If your board will actually allow you to set these (many won't - and you'll know first try), begin with the values Auto determines for RTL and IOL on the populated channels at the stick's base frequency (SPD, not XMP) and note the stepping in each channel. Lower these as sets, leaving all other timings on Auto, eg, you must lower the RTL and IOL for each channel at the same time and maintain any stepping: so if SPD posts with say 60/61 and 10/10 or 10/11, lower the rtls manually say to 59/60 8/8 9/9, 8/9, 9/10, add some VDIMM (25-100mV at a time) and see if it will post. Once you understand the behavior of the sticks and mobo at SPD (when you lower rtl and iol) hold those constant and see how far, if at all the freq can increase with those RTLs and IOLs.
Another approach is to find your best high freq and timing settings, then attempt to lower the RTLs and IOLs in the same stepping until it fails to post (then clrcmos). Every other timing is dependent on the round trip time (RTL) so this can get tricky is ferreting out the lowest RTLs a timing set is compatible with.
Lastly, if the bios has what's called an RTL init, or RTL offset (or both). You can change th eoffset value - but remember it is an offset - the operating value is the offset + value, so check that this actually changes performance. The Init value can be lowered - thre's a formula I have to find around here for setting this in an ideal, but rather conservative manner - it has never improved performance or lowered RTLs for me.
RTLs and IOLs generally increase with frequency, eg; rtls for 3600 will be lower than 4000, but much of that scaling is related to the working CAS at the frequency.
Be advised: RTLs and IOLs are the ultimate rabbit hole. Be prepared to be humbled by tuning these measured values, but many ram/board combos have margins you can capitalize on.
Enough rambling from me.
CptSpig: Try lowering (tRTP) to 6 and raising (tRAS) to 38, (tWTR) to 8. reboot and check your RLT's and IO's.