Tref values

[EMC2]

Well i don't know why on the bios you have these odd settings, 16, 32, 64 and 128. But i'm sure that:
16 -> 10111
32 -> 01111
64 -> 00111
128 -> 11111
Now these settings are all undocumented and maybe for these values of the Tref register we have different refresh rates, but hey here i made some hypothesis and there's no way to test the real refresh values.

Well.... actually there is a way to test/verify the Tref values While I had my DIMMs instrumented anyway, I did The values for the first 3 sets of TRef in the BIOS are fairly close, including the odd low settings.

The BIOS values are the number of MemClocks between refresh cycles (+/-10%). Divider, multiplier, etc. do not matter... only the actual MemClock period... verified for all pre E-rev A64s.

So:: (1 / MemClock) * Bios_Tref = Refresh Period (+/-10%)

Measured actual TRef values(+/-1 clock) in thumbnail below, along with a table for 200Mhz to 300Mhz MemClock, refresh values in uS.

Peace