Hmm You mean its the mighty Celery 300A ?

Perhaps it wants to run at 400Mhz like all such great CPUs should, I have a 300A and it hates being stuck at 300.

On a more serious note it sounds like you might want to change the BIOS battery and see if that helps the settings stick, its possible the battery is getting low on voltage and its causing these errors. If that doesnt work you might want to see if flashing the bios with the latest version helps.

The otehr possibility might be the BIOS rom itself is failing, Ive seen this happen to older boards.

Nah, the Covington is the Klamath without L2.
There is absolutely no reason to have a Covington in use, except if you want to overclock a really bad CPU.
On stock clock you'd get same results with Klamath or Deschutes @ 66 MHz and disabled L2-Cache.

Due to the lack of L2 cache a Covington accepts FSB overclocking much better than the Klamath.

Disruptor wrote on 2024-02-10, 10:34:

Nah, the Covington is the Klamath without L2. There is absolutely no reason to have a Covington in use, except if you want to ov […]
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Nah, the Covington is the Klamath without L2.
There is absolutely no reason to have a Covington in use, except if you want to overclock a really bad CPU.
On stock clock you'd get same results with Klamath or Deschutes @ 66 MHz and disabled L2-Cache.

Due to the lack of L2 cache a Covington accepts FSB overclocking much better than the Klamath.

Yes, my bad 300A is Mendicino with 128k L2.

Id still recommend OP gets a 300A, they are far cheaper than buying a good Pentium II 450 and a good 300A will happily clock to 450.

PlaneVuki wrote on 2024-02-10, 09:27:

Hi.

I have covington 300 slot1 cpu and ga-bx2000 mobo.

Using them together, the pc sometimes starts as 266mhz and sometimes 300mhz (same bus 66.66mhz, no overclocking, I am not changing anything in bios or jumpers).

Where are you checking the CPU frequency? Windows, or what's reported during POST?

PlaneVuki wrote on 2024-02-10, 09:27:

Using them together, the pc sometimes starts as 266mhz and sometimes 300mhz (same bus 66.66mhz, no overclocking, I am not changing anything in bios or jumpers).

Any idea whats going on? Isn't this cpu have locked ratio? How can I control the ratio myself then?

According to the mainboard manual, the ratio is controlled using the first four DIP switches. 266 @ FSB66 and 300 @ FSB66 only differ in the setting of the first DIP switch. If the processor indeed boots at different clock rates (and it is not just a fluke in the BIOS speed display), the issue might be a contact issue in that DIP switch. If set to 266 (first switch on), but the contact is bad, you will get 300 instead.