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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 20 Sep 2021 12:45:52 -0700
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Subject: Re: [PATCH v2 0/4] Introduce and use absolute_pointer macro
To:     Matt Turner <mattst88@gmail.com>
Cc:     Ulrich Teichert <krypton@ulrich-teichert.org>,
        Michael Cree <mcree@orcon.net.nz>,
        Guenter Roeck <linux@roeck-us.net>,
        Richard Henderson <rth@twiddle.net>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        "James E . J . Bottomley" <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        alpha <linux-alpha@vger.kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-parisc <linux-parisc@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        Sparse Mailing-list <linux-sparse@vger.kernel.org>
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On Mon, Sep 20, 2021 at 11:59 AM Matt Turner <mattst88@gmail.com> wrote:
>
> In the decade plus I've been around Linux on alpha I've don't actually
> recall hearing of anyone using Linux on a Jensen system before :)

Looking around, I'm pretty sure the system I did all my initial work
on was a Jensen.

This is from the linux-.1.1.83 patch:

- * I don't have any good documentation on the EISA hardware interrupt
- * stuff: I don't know the mapping between the interrupt vector and the
- * EISA interrupt number.
- *
- * It *seems* to be 0x8X0 for EISA interrupt X, and 0x9X0 for the
- * local motherboard interrupts..
+ * The vector is 0x8X0 for EISA interrupt X, and 0x9X0 for the local
+ * motherboard interrupts.. This is for the Jensen.

So yup, my initial bringup machine was that DECpc AXP 150, aka "Jensen".

The IO subsystem on that thing was absolutely horrendous. Largely
because of the lack of byte/word accesses, so doing any PCI accesses
had to be encoded on the address bus. Nasty nasty nasty.

The original design with only 32-bit and 64-bit memory accesses really
was horribly horribly wrong, and all the arguments for it were
garbage. Even outside of IO issues, it blew up code size enormously,
but the IO side became truly horrendous.

Oh well. Water under the bridge.

I did have another alpha at some point - going from the original
150HMz EV4 to a 275MHz EV45. I forget what system that was.

               Linus