[SATLUG] IBM 5140 Convertible

Bruce Dubbs bruce.dubbs at gmail.com
Mon Jul 23 19:09:04 CDT 2012

Craig wrote:
>> On Jul 23, 2012 2:44 PM, "Bruce Dubbs" <bruce.dubbs at gmail.com> wrote:
>>> Joe wrote:
>>> So, I just acquired one of these.  Its in great shape and I'd like to get a
>>> Linux or BSD (something with a c compiler) on it. ...  well,  there's no
>>> persistent storage, aside from a pair of 720kb floppies.  It's an 80c88
>>> processor with 256kb of RAM and a modem. Any recommendations?
>> DOS.  Linux never ran on anything less than a 80386.

> Ummm... I know one can hardware upgrade an original C64 to 286 speeds,
> but Lunix does run nicely on a standard stock c64 running at 1Mhz.

It's not a speed issue.  It's memory addressing.  An 8096 or 8088 only 
has 20 address bits formed from a segment register and a general purpose 
register.  (You can trick it to get an extra 64K addressing.) That's why 
Linus rejected it.

There may be an 8086 version of Minix that might work.  There may be an 
old BSD version that works too.  But Linux?  No.


Look at boot/head.s

  *  head.s contains the 32-bit startup code.
  * NOTE!!! Startup happens at absolute address 0x00000000, which is 
also where
  * the page directory will exist. The startup code will be overwritten by
  * the page directory.

There is no 32-bit mode or page directory on an 8086/8.

   -- Bruce

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