Feelings about vintage systems

Don THX1138 at dakotacom.net
Thu Aug 24 18:35:06 CDT 2006


Jim Leonard wrote:
> Chuck Guzis wrote:
>> I'm glad that IBM didn't decide on the 8275
>> as the CRT controller.  That would have been a big mistake.
> 
> I can't find any information on the 8275 -- why would it have been a big 
> mistake?

<groan>  It is *such* a brain-damaged part!!  If you want to
do something mindless (e.g., an MxN pure text display) it
is only mildly annoying.  (though it buys you very little!)

OTOH, if you want to do something like build a "real"
terminal, etc. it is atrocious!  You have to pass lines of
text to it "on demand" (IRQ).  "Attributes" take up
display cells (so, if you have a blinking character in
row 1, the address of the characters in row 2, for example,
are not "simply" X+length_of_row but, rather,
X+length_of_row+num_attributes_between_there_and_here, etc.

There are workarounds for this but it is just an ugly
device to use.  I maintain a product for an old client
that (unfortunately) uses these.  Every time they want
to change the display contents, it is a major effort
to figure out how to fit things together.  I keep hoping
they'll tell me they need a redesign because they can
no longer find those parts... but, they must have a
sh*tload of them hidden away someplace  :-(



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