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From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr)
Newsgroups: comp.sys.dec
Subject: Re: PDP 11/24 VS 11/44
Message-ID: <1990Sep28.033529.550@spcvxb.spc.edu>
Date: 28 Sep 90 03:35:29 GMT
References: <1990Sep25.201504.5605@uunet!konkord>
Organization: St. Peter's College, US
Lines: 37

In article <1990Sep25.201504.5605@uunet!konkord>, jar@konkord.uucp (John Roberts) writes:
> 		Does anyone know which is the faster/better machine?
> 		(The 11/24 or the 11/44)?

  The 11/44. It has:

  o '181-based CPU. The 24 uses a custom 40-pin microprocessor (2, actually)
  o Native addressing to 1920Kw. The 24 needs a KT24 option to go over 248 Kw.
  o Faster floating-point (FP11-F) and CIS (KE44) options
  o Split I/D space
  o More 11/70 compatibility for things like Unix
  o Always in a 10.5" box. Many 24's are in a horrible 5.25" box

> 	Is it possible to take out all the 11/44 boards and replace them
> 	with the 11/24 boards? Are the backplans compatable?

  Nope. The CPU backplanes are dissimilar (the 44 has a dedicated backplane,
the 24 goes in the first 2 slots of a (slightly-modified) DD11-DK. However,
expansion backplanes (DD11-DK, DD11-CK) are compatible, as are the boards
which inhabit them.

> 	What does it mean when the DC ON light blinks and its NOT the
> 	power suppy. Why does the DC ON light blink when grant cards
> 	are not there/or not in the slot?

  DC ON blinks if a power supply voltage is out of tolerance. The most com-
mon cause for this is someone installing a DD11 backplane and forgetting to
cut the battery backup jumpers on it 8-).

  If you have the environmental monitor option (it's a secret option) in the
44, you can also get a DC ON blink if all 3 of your fans are kaput. Watch
out for 44 fans - they are 35V 70Hz *square* *wave* drive and really hard to
get.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381