Subject: Re: PDP-11/73 Cabling Questions

From: [email-masked] (Terry Kennedy, Operations Mgr.)
Date: Wed, 17 Aug 1994 04:25:24 GMT

In article <[email-masked]>, [email-masked] (davis robert) writes:
> The CPU is an M8190 AB (KDJ11-BB); according to the field service listing
> of modules that was posted here, this is a J11 CPU, 15 MHz, with 2 boot
> and diagnostoc ROMs and FPJ11 compatibility (warm floating point but will
> accept an FPA).  What is "warm floating point"?  

  It means that the base processor chip (the J11) knows how to do floating
point math, but isn't very good at it 8-). For floating-point-intensive uses,
it's recommended that you add the FPJ11 floating point accelerator.

> Im guessing that since this CPU runs at 15 MHz and not 18 MHz that it
> is not an 11/83 or higher.  

  This is confusing, so bear with me. There are 4 basic board families that
implement Q-bus CPU's with the J11. They are the KDJ11-A (11/73, dual card
intended for OEM's), KDJ11-B (11/73 [see - I told you it was confusing!] and
11/83, where both are a quad card but the '73 runs at 15MHz and has no factory
FPA and the '83 runs at 18MHz and comes with an FPA), KDJ11-C/D (11/53, in
various forms. The only common ones are the .5 and 1.5MB on-board memory 15MHz
units, although there is an 18MHz flavor with S-box handles for the DECserver
500/550), and KDJ11-E (11/93, 2 or 4MB on-board memory, FPA).

  As you can see, there are two different versions called the 11/73. You have
the one that uses the same base card as the 11/83. Further confusing the issue
are the large number of bugs in the CPU and FPA chips in early releases of the
boards, causing you to find "11/83" boards in the field that have no FPA.

> The memory board used is an M7751 CF. What is the difference between
> this and the CA option type board (listed as 4MB 22-bit parity/CSR MOS
> RAM)?  Are they they the same thing?

  Normally the second letter of the suffix indicates a model variant, but on
memory boards it indicates the vendor of the RAM chips on the board. In this
case, -CA means "no vendor specified" - it's the spec for the module, and -CF
means the board was built with Hitachi chips.

> Also, does anyone know anything about an M3107 board (for serial ports)?
> This isn't listed in the field guide to modules.

  Yes. It's a DHQ11.

	Terry Kennedy		  Operations Manager, Academic Computing
	[email-masked]	  St. Peter's College, Jersey City, NJ USA
        +1 201 915 9381 (voice)   +1 201 435-3662 (FAX)