AWESOME JOB AND POST, i am impressed to see this much detail!!
I think "fastest" XT is the Olivetti PCS86 from 1989, not 1986 as name would suggest. its a 10mhz nec v30, has 640kb main ram, it supports EMS 4.0, but has 2x 30pin sim slots onboard (they are on 16bit a bus, not 8bit bus) that can accept 2x 16mb simms,for 32mb total although i'm 99% sure even with ems 4.0 a 8086/80186/Nec v30 class cpu can only address 16mb memory. It also has has 3x full length 8-bit isa card slots on a riser, ps/2 keyboard & mouse ports, 2x each serial/printer ports, intergrated vga/cga (the pcs86 supports vga upto 640x480x16 & cga 640x400x16 oddly its the exact same as the chipset in the AT&T system in 2nd comparison of scores). it can also take a 16mhz nec v30HL as a upgrade cpu (& be made to also operate at 16.6mhz in the pcs86)
CPU to CPU i'm sure they would equal clock for clock, but the access to the 16mb of ems memory on a 16bit bus tips the scale, especially in terms of "usability". But beating a 12mhz 286...thats JUST MADDNESS...wow
** nec v30's support 8088 emulation mode, 8086 instructions, 80186 instructions & Nec's own v30 instructions... i know some XT IDE cards can take advantage of this via a bios edit/flash... i wonder how far that could take a nec v30HL in terms of "what extra can it do"
** i have read that the pcs86's onboard paradise pvga1a 256kb can be upgraded to 1024kb, but have yet to try it
BUT AGAIN AWESOME JOB AND POST, i am impressed to see this much detail!!
(edited spelling and and order, sorry)