10 Apr
1997
10 Apr
'97
3:46 a.m.
Well I went out yet again today and found a really nice IBM 5155 Portable
PC at the local Salvation Army thrift store. I picked it up and brought it
home, and it works like a champ! The only DOS I had for it though was either
CoronaDOS 1.25 or 2.11, and both booted fine on it, though I can't get either
CP/M-86 or Concurrent CP/M to boot on it. This is an interesting machine
considering it has the full 8 expansion slots in the rear! I think it will
make a nice addition to the Osbourne and Kaypro portables I already have,
though I hadn't planned on adding a PC to the collection at all. Now all I
have to do to round out the portables is find a Commodore SX-64 some day for a
good price. BTW, the IBM has a whopping 256k of RAM.
Jeff jeffh(a)eleventh.com
--
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// Amiga: Today's Technology Ten Years Ago
// -------------------------------------------------------
\// True 32bit pre-emptive multitasking GUI, plug&play hardware,
\/ stereo sound, and 4096 color video modes since day #1
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Collector of classic home computers:
Amiga 1000, Atari 800, Atari 800XL, Atari Mega-ST/2, Commodore
C-128 & C128D, Commodore Plus/4, Commodore VIC-20, Kaypro 2X,
Mattel Aquarius, Osbourne Executive, Sinclair ZX-81, TI-99/4A,
Timex-Sinclair 1000, TRS-80 Color Computer-3, and a TRS-80 Model 4.
Plus Atari SuperPong and Atari 2600VCS game consoles.
11 Apr
11 Apr
2:59 a.m.
Well I went out yet again today and found a really nice IBM 5155 Portable
PC at the local Salvation Army thrift store. I picked it up and brought it
In case you've not spotted it, most of that machine is built from standard
IBM parts.
The motherboard in that machine is a standard XT one. The video card is a
standard IBM CGA card (although the monitor is monochrome, and plugs into
the modulator connector), and the floppy controller is the standard PC/XT
one
What is different is the PSU (different output cables and box, otherwise
pretty standard), the drives (half-height, or as IBM call them 'slimline
drives'), and the monitor. The latter seems to be a Zenith composite video
monitor.
Schematics for everything but the PSU are in the appropriate TechRefs
(PC/XT and Portable Techref for the motherboard and keyboard, Options and
Adapters TechRef for everything else).
good price. BTW, the IBM has a whopping 256k of RAM.
If you want 640K without wasting a slot, here's what to do :
Remove the motherboard (Yes, it's a pain to do so - you have to remove the
drives first to get at one of the screws!)
Remove banks 0 and 1 of RAM chips and replace them with 41256 (or
equivalent) 256Kbit chips. Leave the 64K chips in banks 2 and 3. All the
rams face the same way.
Put a 74F158 (or 157) in the empty 16 pin socket at the front edge of the
board. A slower chip (like a 74LS158) may also work - I will have to
check. This chip faces the same way as the surrounding chips.
Solder a jumper between pads E1 and E2 at the right edge of the board
Reassemble and enjoy 640K :-)
This is an official IBM mod IMHO. My TechRef shows schematics for both
versions of the board.
Jeff jeffh(a)eleventh.com
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
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