|Re: [hatari-devel] test needed on a 4MB STF|
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Le 22/12/2016 à 18:49, Christian Zietz a écrit :
Nicolas Pomarède schrieb:
We know that if we access an address > mmu_size0 + mmu_size1 then we get
an "empty" region up to 4MB where the STF will return the last word seen
on the bus
When you say "empty region", you probably mean that no RAM access
signals (/RASx, /CASxL, /CASxH) are being generated, right? I have to
look up how the rules for generating these are.
From an HW point of view, I don't know if the MMU doesn't generate any
RAM signal, I guess it's the case.
If RASx/CASxL/CASxH are not generated with the correct timing of the
"read cycle" chronogram for example (as detailed in the OKI 41256
datasheet), does it mean the ram modules doesn't change its previous
output state, which would mean the 16 RAM modules would keep their
latest Dout value ? (usually this is the last word prefetched by the 68000)
If so, I understand why RAS/CAS would not be generated when accessing
addresses beyond mmu_size0 + mmu_size1, but I don't see why it would
also be the case with this 128/2048.
Might be some bit combinations again that are supposed to work when we
go beyond total ram, but that triggers in some unexpected cases too.
Do you see this "hole" too on your STFs between 40000 and 80000 ?
I'll see if I can do the test later.