24 Apr
2008
24 Apr
'08
4:44 p.m.
On Thu, 24 Apr 2008, Jules Richardson wrote:
Does anyone recall what the maximum memory was for an
original IBM 5150 PC at
launch time?
640K, although going past something near but not exactly 512K? required
some minor software patches
. . . with other trivial software patching, video memory space could also
be used.
The way I recall it, IBM only offered 64KB expansion
cards back in the day
(256KB ones came later) and the 5150 would only take four of them (wasn't the
fifth expansion slot wired differently or something)?
Nope fifth slot was same.
But that was true about the eighth slot of XT.
However, you MIGHT want video. or FDC or serial or parallel
That still gives a maximum of 320KB of memory though
(4 x 64KB, plus 64Kb on
the motherboard) - yet I was remembering the maximum total memory as being 256KB.
Maybe just bit-rot on my part.
Or did the motherboard memory somehow get
disabled if memory expansion boards were in use?
no
Or was there some kind of
maximum limit dictated by the 5150's BIOS?
I don't think so, BUT, the
switch settings (one of the dipswitch blocks of
5150 was to tell the BIOS how much RAM was installed)
I'm sure other things could be done later on via
third-party boards of course
(or via the 256KB expansion boards), but in the context of the thread that I
found myself involved in, the question was what the maximum memory config in a
5150 at launch time was...
The first of the aftermarket memory boards were available before you could
get a 5150 without being on a waiting list. Some of the aftermarket
memory boards, such as the excellent Boulder Creek board (with ECC!) were
available before most people could get their 5150s.
IBM DID permit selling the machine with keyboard and 16K, NO video, NO
FDC. It was not gray-market (or grey in UK), just that they preferred
selling them stuffed with crap. I could have received a machine a month
before I got mine if I would have agreed to buy the "loaded" machine with
$500 TM100-1s, 3 rows of $200 41156s, EasyWriter and Visicalc (don't
remember the price)
At Merritt college we bought 5150s with CGA board and FDC, and populated
them with aftermarket memory, drives, and monitors. Soon after, IBM
offered an "incredible deal" with big discounts, but only on "loaded"
machines.
--
Grumpy Ol' Fred cisin at xenosoft.com