PDA

View Full Version : The IBM PC AT vs. The IBM PC/XT 286



Great Hierophant
October 5th, 2006, 05:19 PM
Lets us compare the two machines, with the AT in its prime configuration:

AT - Two Models, 319 & 339
XT/286 - One model

AT- Sold from 1986-1990
XT/286 - Sold from 1986-1987

AT- 8Mhz 80286, 1 wait state memory
XT/286 - 6MHz 80286, 0 wait state memory

AT - 512KB on board
XT/286 - 640KB on board

AT - 6x16-bit/2x8-bit slots, all support long cards
XT/286 - 5x16bit/3x8-bit slots, 2 slots only support short cards

AT - Lock and LEDs on Case, Cooling fan
XT/286 - None

AT - 192W Power Supply
XT/286 - 157W Power Supply

AT - 84 or 101 Keyboard
XT/286 - 101 Keyboard

AT - 30 MB Hard Drive
XT/286 - 20 MB Hard Drive

AT - 5.33MHz 80287
XT/286 - 4.77MHz 80287

AT - 22 Hard Drive Types
XT/286 - 23 Hard Drive Types

Mike Chambers
October 5th, 2006, 11:53 PM
interesting comparison....

stock vs. stock, the AT looks a little better. however, if you wanted to buy either one stock and upgrade it a little bit the XT can be made better for less money. it already has 0 wait state RAM(and more of it)

even though the clock speed is a bit faster on the CPU in the AT, 0 wait state can help quite a bit speed wise during reads and writes to the RAM.

i'll take both of them though, just UPS em to me... :)

the xt guy
October 6th, 2006, 03:35 AM
the IBM PC-AT was discontinued on April 2, 1987 when IBM introduced the PS/2 series and discontinued the entire PC/XT/AT line in one fell swoop.

IBMMuseum
October 6th, 2006, 08:44 AM
Lets us compare the two machines, with the AT in its prime configuration:

AT - Two Models, 319 & 339
XT/286 - One model

AT- Sold from 1986-1990
XT/286 - Sold from 1986-1987

AT- 8Mhz 80286, 1 wait state memory
XT/286 - 6MHz 80286, 0 wait state memory...

The AT was IBM's flagship of the time, with a no-holds cost as well. For the much more rare XT 286 I think it was to rid excess XT case and power supplies, coming up with a model that was lower cost. Just look at the short production dates.



AT - 5.33MHz 80287
XT/286 - 4.77MHz 80287

On both of these platforms (and the PS/2 Model 25 286 / Model 30 286) the 80287 NPU is run at 2/3rds CPU clock. This was done for a timeframe where the lower speed 287 NPUs were more common and less expensive than higher speeds. Easy to field-modify this if you have an 287 as fast as the 286 CPU (or reasonably close / with heatsink to reliably work) by cutting the ground trace to pin 39 of the 287 socket and tying it to +5VDC.

Probably the IBM PS/1s based on the 286 are the same way. For the PS/2Model 50, 50Z, & 60 (which are the only microchannel PS/2s based on the 286) the 287 is run at same speed as the 286 (10MHz). Many clone 286 motherboards, especially those able to run the 286 at speeds above 10MHz, had a jumper setting to adjust this.