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PC vs. AT: reasons to own one over the other

kantexplain

Banned
Joined
Aug 14, 2023
Messages
92
In my experience the plain jane AT clone case couldn't take a 5170 motherboard. The case could be easily modified (with a hacksaw) if you had the stomach.

I had thought that "baby AT" was or at least arose as a term to denote 286 based mobos with 16 bit ISA slots in a 5160 form factor. There was the Bullet-286, that actually fit in a 5150 case iirc. I guess most of these factors and terms were in flux.

Would a 5162 mobo fit in a 5160 case? Would it fit in a 5170 case?
 

krebizfan

Veteran Member
Joined
May 23, 2009
Messages
6,211
Location
Connecticut
The AT clone I had was almost identical to the IBM AT except that one megabyte could be installed and the bay under the floppy drives was also opened to outside.

Baby AT seemed to develop into a combination standard: based on the smaller IBM AT motherboard but also able to fit in an XT case with the necessary mounting points for either case.
 

basman74

Experienced Member
Joined
Feb 16, 2010
Messages
124
I never bothered to keep my 286 boxes. The 386 boxes were compatible and more capable. I still have a couple 8088 boxes, however.
Indeed. Had several 286 clone systems but those never stuck around long. My 80386 and 8088 systems lingered the most. :)
 

kantexplain

Banned
Joined
Aug 14, 2023
Messages
92
The AT clone I had was almost identical to the IBM AT except that one megabyte could be installed and the bay under the floppy drives was also opened to outside.

Baby AT seemed to develop into a combination standard: based on the smaller IBM AT motherboard but also able to fit in an XT case with the necessary mounting points for either case.
I suspect that an actual AT board wouldn't fit in that case. I had 1 that had the same mount points as am AT, but at least 1 type of AT would protrude into the bottom part of the drive cage. Again a simple enough job if you had a hacksaw. But clone cases didn't necessarily have IBM AT board access, and why would they. I had a couple of Dell 286 boards that were rectangular, unlike IBM boards. Did Dell create the clone AT standard that the case makers limted their products to? I haven't looked at a BYTE or PC Mag in ages. Chances are you couldn't glean all necessary details from ads alone. Maybe in articles though. Or rather something like Aubrey Pilgrim's books? I don't recall ever seeing an article that described building a clone. Then again mayne Radio Electronics did. Or Computer Shopper? Both had articles on building a Hackingtosh. And 68000 based units in PC style cases.
 

dfawcus

New Member
Joined
Dec 24, 2023
Messages
8
it might be fun to play with some of the more obscure examples of software/OSes that run in Protected Mode (the holy grail is probably the abortive attempt by Digital Research to make a 286 version of Concurrent DOS; that only runs on certain revisions of the 286 chip because Intel kept changing some undocumented instructions out from under the DR developers).

That "holy grail" code is now available to try and run, one can find it on bitsavers. I've been trying to get it working on simulated environments (86Box), but have been having to work on it in a debugger, as there are timing issues in some driver code.

To date I've not got much beyond live disabling the floppy disk driver, so as to avoid a panic there, but got distracted before getting too much further. Working on an actual physical 286 (hence with correct period timing) might make things easier. I was thinking of maybe getting an 8-12 MHz 286 board, and seeing if that helped, however the latter might also be too fast.

See https://bitsavers.org/bits/DigitalResearch/FlexOS/FlexOS_286_1.3_Dev_Kit.zip for the initial system, and https://bitsavers.org/bits/DigitalResearch/FlexOS/FlexOS_286_1.42_Dev_Kit.zip for the slightly easier to debug version I'm currently playing with (off an on).
 

paul

Veteran Member
Joined
Mar 18, 2004
Messages
816
Location
New Zealand
To me the IBM AT is the collectable machine as it represents the basis of the modern PC, where the PC or XT is too removed. It's still almost entirely stock with a 5153 monitor, but I've got a Tecmar Graphics Master card in it, a $500 upgrade in the day.

My AT and 2x PCs are the only x86-class machines in my collection, which I have to keep small anyway. One PC I've upgraded with a period-correct hard disk and controller because I never found a pristine XT to fill that gap.
 
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