From: utzoo!decvax!ucbvax!CAD:tektronix!zehntel!sytek!menlo70!hao!seismo!rlgvax!guy
Newsgroups: net.micro
Title: Re: BLIT workstation
Article-I.D.: rlgvax.1175
Posted: Fri Mar 11 18:01:07 1983
Received: Mon Mar 14 03:21:07 1983

I noticed that the workstation mentioned has a BLIT (with 68000) AND a 2B
(Bellmac-32?  Rumor has it that Bell will release its 3B-5 Bellmac-32 based
UNIX box) CPU.  I have noticed that several small systems - including single-
user workstations - have a separate processor to control the display AND
do NOT have the video memory directly accessible to the CPU.  If you have
the processor doing the text editing/formatting or the graphics or whatever
able to directly access video memory, you can update your screen a LOT faster.
The Alto, the Star, and the Lisa all have the driven directly from CPU
memory, and they all have sexy text and graphics software.  Is there any
reason why a lot of systems being put out now have a "thin wire" connection
between the processor and the display?  Almost all (if not all) of those
systems have a shared-memory connection between SOME processor and the
CRT controller - but a lot of them have something like a Z80 or so to control
the display, and force the 8086 or 68000 or whatever to shove the characters
or bits through a relatively slow pipeline to the memory.  Is there a reason
why this is done?  Is it the extra cost of the dual-ported memory?

					Guy Harris
					RLG Corporation
					...!decvax!mcnc!rlgvax!guy