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 Post subject: What are test registers?
PostPosted: Wed Nov 08, 2017 8:41 am 
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I have read about test registers tr0-tr7 but their usage is nowhere! What they are doing?

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 Post subject: Re: What are test registers?
PostPosted: Wed Nov 08, 2017 9:13 am 
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Hi,

ARISTOS wrote:
I have read about test registers tr0-tr7 but their usage is nowhere! What they are doing?


These registers existed on 80486 CPUs (and nothing else), and were used to allow CPU's cache to be tested for hardware faults.

Older CPUs (80386 and older) didn't have cache built into the CPU and didn't support the registers. For newer CPUs (Pentium and later) Intel removed these registers, and for some and not others (e.g. Pentium II but not Pentium) implemented cache testing as model specific registers instead.


Cheers,

Brendan

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