Re: /proc/cpuinfo incomplete for AMD 386DX 40?

John O'Donnell
2002-06-27T21:52:37Z

OK - Thank you all - I feel better now. :-)
I tried fooling with the cache to no avail. still 5.17
But I dont care - Linux humms on this minor beast of a system.
I was just looking for some clarification and I got it.
Now I can put the 386 back in the closet and let it fun a few years more! :-)
Thanks again!
Johnny O

Willy Tarreau wrote:
> Hello!
>
>>>bogomips : 5.17
>>
>>bogomips : 7.93
>
> I remember having had this last rate on my Am386DX/40 too, when the cache
> was enabled on the mainboard. If I disabled it, it dropped to about 5.2,
> which might explain differences noticed here. So check if you have some
> cache on your motherboard, and if it's enabled in your bios setup. And
> don't trust these boards with fake plastic chips labelled "write back"
> with no other vendor name, and for which the bios reported "Write Back
> cache ON" instead of a size.
>
>
>>>Is there any harm in Linux not identifying stuff like the manufacturer.
>>>I dont know if the i386 supports any extensions that would show up in
>>>the flags field. Think the bogomips is right?!?
>>
>>The flags field is stuff deduced from doing cpuid calls, so nothing there.
>>The vendor might be a little difficult and might require depending on
>>quirks of specific cpu models (i'm not 100% sure) therefore it would be a
>>waste of memory to do.
>
>
> CPUID was introduced in latest Intel's 486, when there was a lot of relabelling
> of cheaper AMDs to Intel equivalents with higher frequencies (eg: Amd486-50 ->
> i486-66). AMD took the step too at the time they were sending their new
> DX4/write-back core, IIRC. But I've never seen a 386 with a CPUID instruction,
> and trust me, I've searched for many ways to differenciate Intel's from AMD's.
> Even the register values after reset were the same as intel's. And they were
> very hard to catch because you had to reset the CPU and bypass the bios to
> get the values, then restore all its context. The only noticeable difference
> I found was that they didn't prefetch instructions the same way, and when you
> disabled the external cache, you could notice a different pipeline stall depending
> on instruction alignment.
>
> So no reliable means to do what you want without opening the case, IMHO.
>
> Cheers,
> Willy
>
>

--
=== Never ask a geek why, just nod your head and slowly back away.===
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| John O'Donnell | |
| (Sr. Systems Engineer, | http://johnnyo.home.mindspring.com |
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