From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, HTML_MESSAGE,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 26871 invoked from network); 9 Apr 2021 22:29:34 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 9 Apr 2021 22:29:34 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id EEC43944DE; Sat, 10 Apr 2021 08:29:31 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 5EDAB93D6B; Sat, 10 Apr 2021 08:29:07 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (2048-bit key; unprotected) header.d=bsdimp-com.20150623.gappssmtp.com header.i=@bsdimp-com.20150623.gappssmtp.com header.b="aULGa4PZ"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 2A0BE93D6B; Sat, 10 Apr 2021 08:29:04 +1000 (AEST) Received: from mail-qt1-f172.google.com (mail-qt1-f172.google.com [209.85.160.172]) by minnie.tuhs.org (Postfix) with ESMTPS id 9A79E93D69 for ; Sat, 10 Apr 2021 08:29:02 +1000 (AEST) Received: by mail-qt1-f172.google.com with SMTP id y12so5442208qtx.11 for ; Fri, 09 Apr 2021 15:29:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=40879retTqU22mWOxsetf6Mz8Lhsw74RAT4vWn9Gr4Q=; b=aULGa4PZ0/kg/6MUpeZADacP6MDzEK5TVYdWwDmBvliMCcQ5lkFqn795Fv2PhVK9yh Z9qxUoefQhuWehQ+/KIO+4APdvqP9kmBBXnY/vxSTG/fld7XrOof5JgepsiANpKeueXR KhVHjqUfxcBGrXmOZZlnQPc2hz81d9NbS2IgV7NdQEOhE1a4y6uE6kGSk4EtDrvUGshj ff+nYIS3NjeSDgzmUhjlLt7GXs0HmCk421+FJcCeh8vL5Srd5QAE0YcZ4+fajfYdbvnW L+icA6VoeQWSkk5Aby7FPHbBdAYeLtaJVNXi3ZEJFbasCcSicdqPhBzUGY6/QLjO8QBB SsIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=40879retTqU22mWOxsetf6Mz8Lhsw74RAT4vWn9Gr4Q=; b=dWxBaxhSBT5dBO1d+mH1thWxbXkxlsidc/fpijdsPG7pmyDG6gzTuocBkM+7DlttXe N9d6/36qimLykk1azpAua2uiqfEvZIjj4G1XL9NuYW5wYHx7/m+FiQwL1x0qEbP+QU7Y MR8VopIoUICjDe1DjattnjFzfyWHf0GlxHOUh+abIMuRusFzYHsGe1WAk+qW1jGZq5xM psWX8+Djwvj2S8OobAUWn6uan8qq/MItV4l/Ze7kPEAoNmC/01TVsFV6iKu7GDNUGSsx iIDyoPNCBKfVsfZ0kVvq7Vtl91Jjv1ly2GPLQC5/30h0GuvP9+7RSpIVwQjqTie74iVI Kkzw== X-Gm-Message-State: AOAM533SKsazhur3IPAMsO3tt1qLY1erQ8gRNxJvt70LTLuQ7vMWNZFL T1phY5toJ0KzheFUiN0RSyxPtp7ENus6jyt6/oLXdwf4bgWbzg== X-Google-Smtp-Source: ABdhPJwkP57aTLPGxgMYdn4Ks+xHUeTg4KmwObWkGH/dHbB6FdfQ+t14JnNb66t65wqrL+EwhFCy74LLJJdtqngV9CU= X-Received: by 2002:a05:622a:1748:: with SMTP id l8mr14924752qtk.73.1618007341651; Fri, 09 Apr 2021 15:29:01 -0700 (PDT) MIME-Version: 1.0 References: <0BD38829-5E79-4034-BCEF-0555434E52A4@planet.nl> <974CFAC9-6951-4495-B01B-3A6401183815@serissa.com> <202104091832.139IWrYM394698@darkstar.fourwinds.com> In-Reply-To: <202104091832.139IWrYM394698@darkstar.fourwinds.com> From: Warner Losh Date: Fri, 9 Apr 2021 16:28:50 -0600 Message-ID: To: Jon Steinhart Content-Type: multipart/alternative; boundary="000000000000d7e91705bf91b0ca" Subject: Re: [TUHS] SUN (Stanford University Network) was PC Unix X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: TUHS main list Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" --000000000000d7e91705bf91b0ca Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, Apr 9, 2021 at 12:33 PM Jon Steinhart wrote: > Lawrence Stewart writes: > > Regarding the SUN-1 design, I had heard a rumor that it was designed > using TTL > > =E2=80=9Ctypical=E2=80=9D propagation delays rather than worst case, an= d as a result was > fairly > > flakey. > > It's astonishing how common a practice that was back then. > Even into the 2000s. I had a 6-month long war with one of the hardware guys for a time collection ISA card he did. It worked great, the driver worked great. Life was good. We shipped product. 5 years later, the customer comes back and wants a dozen more. So, we got new parts and 4 of the 6 new cards were flakey, 2 were good. Fingers pointed at the device driver, etc. Long months of intermittent troubleshooting continued for 5 months. During this time I build an ISA bus trace card, showed the traces were good and the flakiness was the result of bad data coming back from the card. At which point they brought in a different hardware guy to look at things. He discovered the first hardware guy had built an async circuit with typical delay patterns. One of the parts we used was rated at 200ns, but parts from the flakey board worked at 50ns. Turns out the manufacturer substituted a faster part, so the 'typical' delay propagation worked for this async circuit, but the faster response time would corrupt data from time to time. The design was tweaked to be synchronous with a latch, and the unmodified driver worked perfectly then... Fun times that... Warner --000000000000d7e91705bf91b0ca Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


=
On Fri, Apr 9, 2021 at 12:33 PM Jon S= teinhart <jon@fourwinds.com>= wrote:
Lawrence= Stewart writes:
> Regarding the SUN-1 design, I had heard a rumor that it was designed u= sing TTL
> =E2=80=9Ctypical=E2=80=9D propagation delays rather than worst case, a= nd as a result was fairly
> flakey.

It's astonishing how common a practice that was back then.

Even into the 2000s. I had a 6-month long war with = one of the hardware guys for a time collection ISA card he did. It worked g= reat, the driver worked great. Life was good. We shipped product. 5 years l= ater, the customer comes back and wants a dozen more. So, we got new parts = and 4 of the 6 new cards were flakey, 2 were good. Fingers pointed at the d= evice driver, etc. Long months of intermittent troubleshooting continued fo= r 5 months. During this time I build an ISA bus trace card, showed the trac= es were good and the flakiness was the result of bad data coming back from = the card. At which point they brought in a different hardware guy to look a= t things. He discovered the first hardware guy had built an async circuit w= ith typical delay patterns. One of the parts we used was rated at 200ns, bu= t parts from the flakey board worked at 50ns. Turns out the manufacturer su= bstituted=C2=A0a faster part, so the 'typical' delay propagation wo= rked for this async circuit, but the faster response time would corrupt dat= a from time to time. The design was tweaked to be synchronous with a latch,= and the unmodified driver worked perfectly then...

Fun times that...

Warner
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