Почитал даташит. Вот чего надыбал. MCHCFG—MCH Configuration Register

30 Окт 2003 - 14:42 Unknown BIOS

Почитал даташит. Вот чего надыбал.

MCHCFG—MCH Configuration Register (Device 0)
Address Offset: C6–C7h
Default Value: 0000h
Access: R/W, RO
Size: 16 bits
Bit                                       Descriptions
11:10
                System Memory Frequency Select (SMFREQ)—R/W. The reset value of these bits is 00. The
                DDR memory frequency is determined by the following table, and partly determined by FSB
                frequency.
                FSBFREQ[1:0] =00 SMFREQ[11:10]=01 System Memory DDR set to 266 MHz
                FSBFREQ[1:0] =01 SMFREQ[11:10]=00 System Memory DDR set to 266 MHz
                FSBFREQ[1:0] =01 SMFREQ[11:10]=01 System Memory DDR set to 333 MHz
                FSBFREQ[1:0] =10 SMFREQ[11:10]=01 System Memory DDR set to 333 (320) MHz
                FSBFREQ[1:0] =10 SMFREQ[11:10]=10 System Memory DDR set to 400 MHz (82865PE
                only)
All others are Intel Reserved
Note that Memory I/O Clock always runs at 2x the frequency of the memory clock.
NOTE: When writing a new value to this register, software must perform a clock synchronization
sequence to apply the new timings. The new value does not get applied until this is
completed.

ниже по регистрам fsbfreq:

Bit
1:0
             FSB Frequency Select (FSBFREQ)—RO. The default value of this bit is set by the strap
             assigned to the BSEL[1:0] pins and is latched at the rising edge of PWROK.
             00 = Core Frequency is 100 MHz and the FSB frequency is 400 MHz
             01 = Core Frequency is 133 MHz and the FSB frequency is 533 MHz
             10 = Core Frequency is 200 MHz and the FSB frequency is 800 MHz (82865PE only)
             11 = Reserved

т.е. FSBFREQ - только для чтения, выставляются при инициализации по сигналу BSEL от процессора

Signal Name  BSEL[1:0]          

Type   I CMOS
  
Description                    
Core / FSB Frequency (FSBFREQ) Select Strap. This strap is latched at the rising
edge of PWROK. These pins has no default internal pullup resistor
00 = Core frequency is 100 MHz, FSB frequency is 400 MHz
01 = Core frequency is 133 MHz, FSB frequency is 533 MHz
10 = Core frequency is 200 MHz, FSB frequency is 800 MHz (82865PE MCH only)
11 = Reserved

то есть наиболее очевидное решение - работать с ногами процессора:).
Хотя - интересно, что будет если по адресу SMFREQ поставить 00 или 10 вместо 01, которое у меня должно стоять (насколько я понимаю для моего FSBFREQ 00). В таблице таких соотношений нет - что будет, видимо непредсказуемо... все зарезервировано интелом.
Что думаете?

Разлочка коэффициентов память:fsb для GA-8ipe1000