24 Apr
2008
24 Apr
'08
2:43 p.m.
Date: Thu, 24 Apr 2008 13:45:10 -0500
From: Jules Richardson
Indeed - in the context of the discussion I got
involved in (which was
actually about memory prices, not the PC specifically), we were just
interested in what could be done with a 5150 *when it was new* - and I
think all that IBM offered then was the 64K boards (and of course third
parties didn't exist!)
Yup, but vendors like Quadram and Everex came along pretty quickly.
Lots of folks realized that the 64K limitation was a huge one.
You know, I had a thought - I wonder if those 64K
boards can't be
jumpered beyond the 256KB boundary? Maybe that's why I'm remembering a
256KB limit on the original machines (and using original IBM expansion
boards). Getting around that would mean physically hacking the address
lines/decoding of the boards...
There were also some hacks, since 64K DRAMs were available when the
5150 was launched (why IBM didn't design the planar with jumpers to
select memory type is beyond me). If you were handy with a soldering
iron and an Xacto knife, you could cut-and-jumper your way to 256K
planar memory. The big pain was the soldered-in first row of 16K
DRAM.
I have a booklet from an outfitlled "Purple Computing" that marketed
a little piggyback board that allowed one to leave the first row of
DRAM in. It was basically 4 rows of sockets--you still had to do the
cutting and jumpering, but without removing the 16K DRAM. Anyone
wants the booklet can have it for postage.
I was happy to retire my 5150 and get a genuine Taiwanese clone mobo
with 256K and 8 slots.
Still, PC-DOS would run in 64K.
Cheers,
Chuck