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From: Terje Mathisen <terje.mathisen@tmsw.no>
Newsgroups: comp.arch
Subject: Re: Interrupts in OoO
Date: Tue, 8 Oct 2024 10:33:59 +0200
Organization: A noiseless patient Spider
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Scott Lurndal wrote:
> Brett <ggtgp@yahoo.com> writes:
>> Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>=20
>>
>> Your hardware guys are not interested because they know what you want =
is
>> not useful. ICE probes could give you more info, but that tech is high=
ly
>> secret and dangerous for users to get
>=20
> There are close to a dozen 3rd-party devices that will attach to
> the JTAG port and provide extremely low-level hardware state, including=

> individual flops and rams by reading the scan chains.  For AArch64,
> all the interesting state is directly documented in the ARMv8 ARM
> in the context of a JTAG-like implementation.
>=20
> Hardly "highly secret".
>=20
> Scan chains are clearly proprietary design data.
>=20
>=20
>> , and is fused off for your
>> protection.
>=20
> An option at manufacturing time, or later when the chip is integrated
> into a platform, the platform vendor has the choice of fusing out the
> JTAG/ICE port, which would make sense for a device that needs to be
> highly secure (a firewall or crypto appliance, for example).
>=20
>> You don=E2=80=99t need such data, and would not understand such info i=
f
>> you had it.
>=20
> Perhaps you might not undertstand it.  Likely most others here have dir=
ect
> experience with scan chains, IDEs (or more likely VCS) et cetera.
>=20
I had a (quite expensive) ICE for my 386 computer, by the time the=20
Pentium rolled out, large parts of that functionality had turned into=20
the EMON counters, and so available to everyone who had signed an Intel N=
DA.

Byte July 1994 is where I documented my reverse engineering of those=20
counters, it is (by far!) the most cited paper/article I have ever=20
written. :-)

This showed Intel the error of their ways, and all subsequent cpus have=20
documented those counters.

Terje

--=20
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"