17 Oct
2012
17 Oct
'12
8:17 a.m.
On Oct 17, 2012, at 10:10 AM, Liam Proven wrote:
On 17 October 2012 13:05, David Riley <fraveydank
at gmail.com> wrote:
Are you perhaps talking about PLCCs? Square packages like a QFP,
but with J-leads that can be inserted into and removed from a
socket somewhat more easily? Those were certainly popular for a
number of devices, though I can't recall ever having seen a PLCC
386SX. I can't find any examples on eBay of a non-QFP one,
either. Not saying you're wrong, I'm just curious about what
form they'd take.
Is it possible that there was an upgrade PGA socket present on
386SX motherboards alongside the surface-mounted chip? I sure
see quite a few examples of what looks like that (possibly a
socket for a 387SX instead).
It strikes me that your original question may actually have been
about the 16 MB limit, in which case it's a limit of the S-100
bus and not the 386 in question. Their workaround to provide
more RAM is necessary for the extra eight address bits. The
386SX also has a 24-bit address bus, so if you wanted the full
4GB address range, you'd be out of luck anyway.
- Dave
To my recollection, the 386SX only came in
surface-
mount packages. The N8VEM folks (including the S-100
group) have done a pretty good job of making sure all
their boards can be assembled with only through-hole
parts, which makes it a lot easier for novice solderers
with cheap irons.
I must admit, I hadn't considered this, but on consideration, I'm
pretty sure I saw socketed ones - if only because for a while,
replacing a 386SX with a 486SLC was a popular upgrade option.
WikiP seems to bear me out:
http://en.wikipedia.org/wiki/80386SX#The_i386SX_variant
"The 386SX was packaged in a surface-mount QFP, and sometimes offered
in a socket to allow for an upgrade."
Yes, they were Quad Flat Package things, but QFPs came in a socketed
form sometimes - I fitted a few of them myself, even though I was/am
primarily a software guy.