Re: [Freedos-user] chkdsk for fat32!

[dmccunney <den...@gm...>]

On Sat, Apr 19, 2014 at 4:45 PM, Felix Miata <mr...@ea...> wrote:
> On 2014-04-19 13:01 (GMT-0400) dmccunney composed:
>
>> Er, 486 != XT hardware.
>
>> I still have my original XT sitting on a shelf.  It has a replacement
>> motherboard with a 10 *mhz* NEC V20 CPU, a Hercules graphics card, and
>> two Seagate ST-225 20 *MB* MFM hard drives connected to an add-on
>> controller card.  (They pre-date IDE.)
>
>> If the target is genuine XT hardware, I'm not surprised if a more
>> recent CHKDSK will fail to run.  Among other reasons, it's likely
>> compiled to run on >386 CPUs, and simply won't execute on anything
>> earlier.
>
> The XT CPU is an 8088, which, like the 8086 from which it is derived, is a 16
> bit CPU. The difference between them is the 8088 has an 8 bit IO bus path (an
> IBM cost reduction misfeature incorporated into the XT), while the 8086 has
> 16 bit. The NEC V20 is a functional clone of the 8088 intended to be run at
> higher clock speeds, and with claimed greater internal efficiency. None AFAIK
> can possibly run 32 bit software.
> http://en.wikipedia.org/wiki/List_of_Intel_microprocessors#The_16-bit_processors:_MCS-86_family

Correct.  The V20 featured improved microcode, and could actually
execute 80186 instructions.  I had an app or two back when compiled
for a 286 CPU that would run on the V20.

Reports back then gave the V20 about 5% better performance than the
8088 at the same clock rate, and it was a drop-in replacement, so it
was a cheap speed up.

I also had an AST 6-Pak card with a meg of additional RAM.  AST
supplied software let me use the RAM as a disk cache and a RAMdisk.
My startup created  a 512KB RAMdisk, and copied several most used
utilities to it, and made the ramdisk first in my PATH, and I defined
TEMP and TMP to point to it, for the benefit of things like PKZIP that
could be told where to create temp files..  I also had a 256K disk
cache.  I had a freeware app that could take unused video memory and
allocate it to DOS.  The Hercules card left 64K free, so DOS saw a
702K system.  The rest was seen as EMS memory, and reserved for things
that could use it.  It sped things up a treat.
______
Dennis
https://plus.google.com/u/0/105128793974319004519