[pmmail-list] OT: Display Drivers

[Simon Bowring]

On Thu, 26 Sep 2002 16:29:52 -0700 (PDT), Steve Wendt wrote:

>> <clang!> Sound of my jaw hitting the floor...
>>
>> Interesting, so why did IBM make it so complex? Anyway, perhaps best
>> taken off list.

OS/2 1.x (one of the very first protected mode, mutitasking, 
multithreaded, virtual memory operating systems for intel that
came out in 1987) was written for IBM's PS/2 range and was written 
mainly (exclusively!?) in 80286 assembly language.  I'll just say 
that again: in ASSEMBLY LANGUAGE!  It must have been one of the last
"big" OSs to be written in assmebly language. It must have been a 
HUGE job, and by the time it was in use, 80386s were pretty much the 
mainstream (OS/2 1.x would run on them, but not take advantage of 
their extra features like a "flat 32-bit memory model)!

Although the 80286 could address "lots" of memory (16Mb?), it still
used 64kB chunks like the old 8086 and 8088 befiore it, this made for
complex software and a complex display driver model!

The 32-bit OS/2 2.x that came out in 1992, was highly backwards 
compatible with OS/2 1.x, to the extent of running the same 
device drivers (including display  drivers), however new code 
(apart from low level drivers) was written in 32-bit C. In
fact OS/2 4.x can still run OS/2 1.x drivers and software. IBM
understand the value of "legacy code" and backwards compatibilty
to it's customers - try running Windows 1.x, 2.x 3.x apps
(forget drivers!) on todays Windows!

Eventually a far simplified 32 bit GRADD display driver model
was added, greatly simplifying display driver development (mind
you developing an SMP aware display driver is still not for the
faint-hearted!).

Simon

- pmmail-list - The PMMail Discussion List ---------------------------
To POST to the list, send your message to:
pmmail-list@blueprintsoftwareworks.com

To UNSUBSCRIBE, send a message to mdaemon@bmtmicro.com 
with the first line of the message body being...
UNSUBSCRIBE pmmail-list@blueprintsoftwareworks.com
---------------------------------------------------------------------