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From: jnc@mercury.lcs.mit.edu (Noel Chiappa)
To: TUHS@minnie.tuhs.org
Cc: jnc@mercury.lcs.mit.edu
Subject: Re: [TUHS] Spacewar at Bell Labs [ really paper tape readers and tangentially related things ]
Date: Wed, 15 Jan 2020 11:46:47 -0500 (EST)
Message-ID: <20200115164647.AA0D218C0A2@mercury.lcs.mit.edu> (raw)

    > From: Clem Cole

    > So WD designs and builds a few LSI-11 as a sales demo of what you could
    > do
    > ...
    > he put it on the QBUS which DEC could not lock up because they did not
    > create it as WD had.

Wow! WD created the QBUS? Fascinating. I wonder if DEC made any changes to the
QBUS between the original demo WD boards and the first DEC ones? Are there any
documents about the WD original still extant, do you know?

(FWIW, it seems that whoever did the QBUS interrupt cycle had heard about the
metastability issues when using a flop to do the grant-passing arbitrations;
see here for more:

  https://gunkies.org/wiki/Bus_Arbitration_on_the_Unibus_and_QBUS#QBUS_Interrupts

DEC had previously bent themselves into knots trying to solve it on the UNIBUS:

  https://gunkies.org/wiki/M782_Interrupt_Control#Revisions

so it would be interesting to know if it was WD or DEC who did the DIN thing to
get rid of it on the QBUS.)

    Noel

             reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15 16:46 jnc [this message]
2020-01-15 18:35 ` Clem Cole
  -- strict thread matches above, loose matches on Subject: below --
2020-01-15  6:17 [TUHS] Spacewar at Bell Labs Lars Brinkhoff
2020-01-15  6:34 ` Earl Baugh
2020-01-15  7:10   ` [TUHS] Spacewar at Bell Labs [ really paper tape readers and tangentially related things ] Jon Steinhart
2020-01-15  8:05     ` Earl Baugh
2020-01-15 14:50     ` Clem Cole
2020-01-15 23:40       ` Al Kossow

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