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A/UX 3 should boot reliably now

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- Added a hack to bypass SetUpTimeK, which works on 3.0.0,
  not sure about other versions.
This commit is contained in:
Peter Rutenbar 2015-01-29 23:20:23 -05:00
parent 476a8bb570
commit a66ad6d9b4
1 changed files with 26 additions and 1 deletions
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27
core/via.c
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@ -584,7 +584,32 @@ static uint8_t via_read_reg(const uint8_t vianum, const uint8_t reg, const long
return via->ddra;
case VIA_T2C_HI: {
const uint16_t counter = via->t2c - (uint16_t)_via_get_delta_counter(via->t2_last_set);
uint16_t counter = via->t2c - (uint16_t)_via_get_delta_counter(via->t2_last_set);
/*
* This is a hack to allow A/UX 3.x.x to boot on fast hosts.
* The A/UX 3 kernel calls a function, SetUpTimeK, during boot
* to run a giant drba-to-self loop and time it via T2C.
* If the loop completes too quickly, (quicker than 0x492 E_CLOCK
* ticks on 3.0.0), it rejects it and tries again.
*
* SetUpTimeK reads T2C twice and compares them to determine the
* time elapsed. I don't want to count on getting the order correct,
* however. Therefore, we will fake it out by randomly adding 0x500
* to the the value of the clock whenever it's read by SetUpTimeK.
* By the Monte Carlo method, we'll eventually get a case where
* two sequential reads differ by at least 0x500.
*
* FIXME: optimize this better, stop using coff_find_func()
*/
if (sr_s()) {
coff_symbol *symb = coff_find_func(shoe.coff, shoe.pc);
if (symb && strcmp(symb->name, "SetUpTimeK") == 0) {
if (random() & 1)
counter += 0x500;
}
}
return counter >> 8;
}
case VIA_T2C_LO: {