What was a Terminal Concentration Device in DEC's products?

Paul Koning paulkoning at comcast.net
Sat Jan 29 16:12:41 CST 2022

> On Jan 29, 2022, at 3:58 PM, Noel Chiappa via cctalk <cctalk at classiccmp.org> wrote:
>> From: Paul Koning
>> DH-11 is unusual in that it has DMA in both directions
> McNamara's DH11? (I don't know of another DECdevice of that name.) Per:
>  http://www.bitsavers.org/pdf/dec/unibus/EK-ODH11-OP-002_DH11_Asynchronous_16-line_Multiplexer_Users_Manual_Sep76.pdf
> it's DMA on output only; the input side has a FIFO that has to be emptied by the CPU.

Oh.  That's amazing, all these years I thought it had DMA both ways.  Clearly not.  I wonder how I got that misunderstanding.


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