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From: "Ron Natalie" <>
To: "ron minnich" <>,
	"TUHS main list" <>
Subject: Re: [TUHS] Encoding an ISA: Random Logic vs. Control Stores
Date: Wed, 01 Dec 2021 17:08:58 +0000	[thread overview]
Message-ID: <em26769f4d-6042-4e67-ada5-ee9110250e88@alien> (raw)
In-Reply-To: <>

There seems to be confusion here about microcoding vs. discrete 
logic/LSI.    All but the initial 11/20 (and its variants) are 
microcoded.   That is there is a programmed sequence of operations in 
the execution of the individual instructions.   The less popular 11/60 
even featrued a writable control store.

All of the early PDP-11s were built out of discrete logic.   Relatively 
simplistic combinations of various logic chips, gates, flip flops, etc.. 
   A lot of these were encapsulated into the DEC "Flip Chips" small 
circuit boards to do common sets of operations.   While this is by 
modern standards, crude, it doesn't preclude microcoding and other 
advanced tasks.    I worked on a supercomputer built that way (Denelcor 
HEP built largely out of Motorola 10800-series ECL chips).

As I previously stated, the 11/44 was the last of the discrete logic 
PDP's in 1979.    The later systems were all large scale integrated 
circuit based.  First starting with the LSI-11/03 on the Q bus, quickly 
followed by the 11/23 and the Unibus 11/24.

  reply	other threads:[~2021-12-01 17:12 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-30  8:07 pbirkel
2021-11-30 15:19 ` Ron Natalie
2021-11-30 15:30   ` arnold
2021-11-30 15:39     ` Ralph Corderoy
2021-11-30 18:50     ` Jon Steinhart
2021-11-30 21:45       ` Humm
2021-11-30 23:07         ` Jon Steinhart
2021-11-30 23:18           ` Henry Bent
2021-12-01  5:00             ` Jon Steinhart
2021-12-01  6:27               ` pbirkel
2021-12-01 16:42                 ` ron minnich
2021-12-01 17:08                   ` Ron Natalie [this message]
2021-12-01 21:56                   ` [TUHS] Encoding an ISA Warren Toomey
2021-12-01 13:59 [TUHS] Encoding an ISA: Random Logic vs. Control Stores Paul Ruizendaal
2021-12-01 14:55 Douglas McIlroy
2021-12-01 20:27 ` Jon Steinhart
2021-12-01 21:14 ` Lawrence Stewart
2021-12-01 22:09   ` Jon Steinhart

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