VOGONS


First post, by Hatta

User metadata
Rank Member
Rank
Member

I have a 486DX2/66. My BIOS defaults to an AT Bus Clock of CPUCLK/6. Does this mean I'm overclocking my AT bus to 11MHz, or does that mean my CPU is running at 50MHz?

Reply 1 of 4, by nuno14272

User metadata
Rank Member
Rank
Member

cpu clock = 66mhz
AT divider /6 = 11mhz... from default 8mhz.. but 11 usually doesn't afect the isacards. above that theres chances of instability.

does your bios as an option for /8 divider ?

1| 386DX40
2| P200mmx, Voodoo 1
3| PIII-450, Voodoo 3 3000

Reply 2 of 4, by ultimate386

User metadata
Rank Member
Rank
Member

It's not actually running at 66/6. The DX2 internally clock doubles to 66MHz, but the way the system sees CPUCLK is 33MHz. So with /6, you're getting 5.5MHz.

AMD386/IIT387DX40, 32MB, ATi Mach64, AWE64
Compaq Prolinea 4/33, 32MB, Tseng ET4000, SB16
AMD X5, 64MB, S3 Virge/Voodoo1, AWE64
AMD K62+550, 256MB, Voodoo3, AWE64 Gold
P3 1.2Ghz, 512MB, Radeon 7500/Voodoo2 SLI, SB Live!

Reply 3 of 4, by konc

User metadata
Rank Oldbie
Rank
Oldbie
Hatta wrote on 2020-12-17, 13:40:

I have a 486DX2/66. My BIOS defaults to an AT Bus Clock of CPUCLK/6. Does this mean I'm overclocking my AT bus to 11MHz, or does that mean my CPU is running at 50MHz?

None of the two 😉
The CPU runs internally at double (DX2) the bus speed, which is 33MHz.
Your BIOS just defaults to a safe setting so that the computer will always power on.
I believe that although it says CPUCLK it's actually the bus speed, so the correct divider should be 4.
Everyone, please correct me if I'm talking nonsense here