On Sat, Apr 19, 2014 at 4:45 PM, Felix Miata <mrma...@earthlink.net> 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 ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/NeoTech _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
