IBM 5161

From: Fred Cisin <>
Date: Wed Apr 2 13:09:01 2003

On Tue, 1 Apr 2003, Bill Allen Jr wrote:
> The ibm 5161 expansion box was designed for use with
> the ibm pc.
> the exp box added a hard drive to the system and
> provided extra card slots ( i think the box also had
> additional bios or came with an extra fixed disk rom
> chip that went into the pc).
NOT for the hard disk.
> i cannot remember if it is slot specific or if it can
> go into any slot - there is a plate on the pc's back
> that removes to allow the ribbon cables to exit the
> case.

The slots on the PC are wired in parallel. There is NO electrical
difference between them, other than physical distances.
But in the XT, one slot is different. At the time of the release of the
XT, IBM was worried that people would use that slot for something
incompatible, and they had a giant surplus of serial (RS232 and current
loop) cards that nobody wanted, so they provided a "FREE" serial card to
block off that slot.

> the pc xt has a large enough power supply to support
> a hard drive as well as the bios to operate one and it
> has eight card slots.

The XT BIOS does NOT include hard drive support. The ROM that includes
that extension to the BIOS is on the XT hard drive controller card. The
AT was the first to include hard drive support in the motherboard BIOS.
All but the very earliest 5150s had a BIOS that would scan for additional
ROMs, and other than number of slots and power supply inadequacy, would
take a hard drive EXACTLY the same way as an XT.

I think that the 5161 CAN be used on an XT, if eight is not enough.

BTW, IBM called it a "FIXED DRIVE", instead of calling it a "HARD
DRIVE". At their "Technical Briefing" when they introduced it,
they said that that was "because "HARD DRIVE" might sound like
it was "hard to use", and therefore "FIXED DRIVE" would have better
connotations". Some wise-ass in the audience said, "... in a VETERINARY
They also called the motherboard a "SYSTEM BOARD", due to possible
associations of "MOTHERBOARD" with the usage of the word "MOTHER..."
by the Black Panthers, et al.

Grumpy Ol' Fred
Received on Wed Apr 02 2003 - 13:09:01 BST

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