31 Jul
2013
31 Jul
'13
5:02 p.m.
On Wed, 31 Jul 2013, Michael Holley wrote:
The original IBM 5150 had 4 rows of 16K DRAM for 64K
max on the motherboard.
BEFORE the XT 5160 came out, the PC was updated to a
64K/256K motherboard.
Unlike the XT, WHICH CAME SLIGHTLY LATER, the PC had 5 expansion slots,
and a cassette port. Some "journalists" called the 64K/256K PC a
"PC2",
but IBM never used THAT terminology.
Considering the shortage of slots on the Apple2, what does the design with
5 slots tell you about IBM's ability to learn from OTHER people's
mistakes?
The 64K/256K could be upgraded with trivial ease to 640K, by replacing two
rows of 64K chips with 256K chips, and adding one additional chip (don't
remember what that add-on chip was.
When the XT was released the PC was upgraded to 4 rows
of 64K DAM for 256K
max. I bought my IBM 5150 in March 1983. (Just before the XT came out.)
XT
eliminated the cassette port, and incresed from 5 to 8 slots, although
ONE slot (closest to the power supply) skipped one buffer and was
incompatible with some cards. IBM solved THAT by plugging the hole with a
"FREE!!!" serial/20mA card (which they had excess inventory of, and
couldn't sell well because EVERY multi-funcion card had serial.
Q: You and every other multi-function card vendor have clock, RAM, serial,
and parallel. That's 4 functions. How do you compete with EVERY OTHER
4 function card?
A: You call your card "SIX function". You do THAT by adding a RAM-DISK
program (similar to the PC-DOS VDISK), and a PRINT-SPOOLER.
NOTE: The AST and Quadram FPUIB docs have been claimed.
complete system (computer, floppies, monitor and
printer) was $3600 and
my employer reimbursed $1200.
My employer (college administrators, may they rot in pieces) offered "HALF
PRICE!", but the deal was NOT half price of your choice of parts; it was
"half price" at ~$2300 for a system bundled with every piece of crap that
wasn't moving, such as Easy Writer.
There were many third party cards available. The AST
Six Pak IO/ RAM board
held 384K of RAM, the old PC would then have 448K and the new PC/XT would
have the magic 640K.
The multi-function cards started coming out in 1982. WELL BEFORE THE XT
5160. With 5 expansion slots, a complete system needed mult-function.
But, the first after-market board that I bought for mine was the Boulder
Creek Systems? RAM card - 192K with ECC!
--
Grumpy Ol' Fred cisin at xenosoft.com