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PCMCIA or USB to DB9 serial port adapter

Discussion in 'IBM Thinkpad' started by none, Jun 8, 2007.

  1. That's interesting. The motherboard I was playing with at the time had the
    IBM/Cyrix 486SLC2-66 "chip" on it, which was, as I understood it, a
    fuel-injected '386 with a '387 "bolted" on. But, IIRC, it did have the 8259
    interrupt controller(?).
    LOL! I was totally lost, then, so I just called the guy who gave me the
    board and the (fully licensed) copy of Warp 3 and asked how he got the
    printer to work without spewing pages of nonsense.
    All I knew back then was what Chuck Forsberg, et al., told me, that the
    8250A/16450 was a brain-damaged UART, and I needed at least the 16550AF to
    work right, or I'd have to turn on CTS/RTS handshaking. Dropping RTS during
    disk writes would slow things down, but it would prevent data overruns.
    LOL! Still, it would've been interesting.
    Tandy had a lot of good ideas, I guess, but since they were the only ones
    supporting their machines, they didn't go anywhere. They had some downright
    boneheaded ideas, too, like integrating the power leads into the data cable
    for the floppy drive, without changing to a different type of connector,
    cable, or *something*.
    LOL! So, what did "100% IBM Compatible" mean, anyway? Sounds like just a
    marketing phrase.
    Tom Rutherford, Jun 19, 2007
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  2. none

    Mike Y Guest

    Actually, the 'SL' chips were 'system management' chips. I'd have to go
    and check on that specific chip to be absolutely sure, but the SL family
    was designed for laptops and power management. The SMI (system
    management interrupt) was a 'system interrupt' that was higher priority
    than an NMI. It could interrupt anything and everything. When invoked,
    it also made a beautiful flat memory model. Also, in the SL chips you
    could pretty much read back all kinds of stuff that was otherwise
    'write only'. Ie, you could get into things to find out actual state and
    it for a suspend/resume.

    I tried writing a simple debugger in SMmode, and it worked, but I didn't
    get very far with it. I DID write a memory manager that use SL registers
    though. It was the equivilent of a 'real mode' EMM386.SYS program,
    and used the SL enhanced memory interface to do the same thing with
    memory as EMM386.SYS did. At one point I took that program and
    ripped the SL stuff out but just put memory management in that used
    other means. Like banked mapped memory. Or, just putting SRAM
    chips in my IBM-PCAT that was an 80286. I called the program
    UBMPRO for Upper Memory Block PROvider. I ran HIMEM.SYS
    and then UMBPRO on my PCAT with a memory card and with all the
    stuff in UpperMemory, my 8mhz '286 PCAT had 639K free (with all
    the stuff loaded) and was faster than a 16MHz '386 I had with both
    running MSDOS 5.0.

    Hey, that was their right! They DEFINED the term, right? Actually, while
    the entire IBM PC design has some braindead aspects to it, overall it is
    kind of neat. Could it have been done better? Sure. At least it's not as
    bad as Apple with the first Mac! 'IWM' for the floppy? Software SIO?
    Come on, even the Radio Shack Color computer had an FDC!

    As to the CardSoft package, IBM paid for that implementation, so they
    got it. That's only fair.
    Mike Y, Jun 19, 2007
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  3. Okay...I was talking about the microprocessor, the 486SLC2-66, but I forget
    now why I mentioned it. Maybe since IBM had a hand in it, I was thinking
    that its peripheral chips would behave better than the standard chips. I
    dunno. Might've been sleep typing again.
    With SRAM?!?! I'll bet it *did* scream, but you had a king's ransom worth
    of memory in there!
    Tom Rutherford, Jun 21, 2007
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