The shadow memory options (Video BIOS Shadow, C800-CFFF Shadow, etc.) are used to put the respective ROM memory addresses into 'shadow RAM', a special portion of memory set aside by the motherboard's memory controller. (This is not related to cache memory; shadow RAM is a portion of your DRAM set aside for such a purpose.) The reason for wanting to do this is to increase performance of any ROMs that may be located in said memory spaces, as RAM is usually much faster than ROM. Sometimes this causes some problems when you try to update the BIOS of said cards with ROM chips in the respective ranges, so you can manually disable shadowing for these regions when need be.

ISA I/O Recovery adds wait states to accesses to the ISA bus, which may help cure things like lockups, data corruption, weird glitches, etc. when using a CPU that is a bit faster than certain ISA cards may like to talk to. (I'm thinking of cards with Yamaha OPL3 FM synthesis chips, though sometimes ISA network cards need a little extra time as well.) On a fairly fast system like the one you've got, there will typically be little observable difference in performance with this enabled or disabled, so don't be too quick to turn it off if it's already on.

Generally you'd want PCI Fast Back-to-Back Transaction enabled, unless you run into glitchiness with PCI video or SCSI cards.

Hidden Refresh tells the motherboard's memory controller to handle memory refresh without bothering the CPU about it. With this off, the CPU has periodically drop whatever it's doing to to refresh the memory in the system, which can eat a fair bit of the CPU's time. Basically enabling this improves performance, though if you're trying to use memory chips that aren't really up to the speed you're running the CPU bus at (say, trying to run 70ns chips on a 60 or 66MHz Pentium FSB) then enabling this will increase the chance of you running into memory errors. Also some marginal motherboard chipsets don't necessarily do a good job of this so you may have to disable this even if the memory seems fast enough to work otherwise. Usually you can leave this enabled though.

HDD Block Mode is a performance enhancing feature for the IDE hard drive, which enables multiple-sector transfers to the HDD(s) connected to the IDE channel(s). Some really old IDE hard drives and early builds of Windows 95 (pre-OSR2 mainly) and OS/2 sometimes didn't work well with block mode transfers during setup, so the manufacturers allowed this to be disabled when needed.

CPU to PCI write buffer should be ON. That enables a FIFO buffer of sorts between the CPU and PCI interface and will improve performance.
CPU to PCI Byte Merge is another performance enhancing function, I don't know exactly how it works but generally you leave that on unless you get weird problems with video or network cards.
PCI to DRAM Buffer should be ON. Similar with the CPU to PCI write buffer, except this enables a FIFO buffer between the PCI bus and memory controller. Only turn this off if you run into weird problems.

thank you for your help

it deffo explains more and understand better

i should leave the shadow rom settings where it is

-leave the the isa i/o recovery on
-turn on pci fast back to back
-i did try the hidden refresh and the system hangs during post - so maybe best to leave that off

as i am use a cf to ide adapter - is it best to have hdd block mode on or off

basically turn on all pci buffers

Yeah, that's pretty much the gist, leave all the buffers on unless you have a reason to turn them off (troubleshooting crashes/glitches, etc). For CF to IDE, try turning Block Mode on and off, and see if there's any measurable performance difference between the settings. Off is always the 'safest' option though, but 'On' might be faster.

One little gotcha with Byte Merge: certain video cards and chipset combinations (PCI Voodoo3 for instance with some strange motherboards) may be more stable/reliable with Byte Merge disabled. But if it works well while it's on, then no need to muss with it.

Hidden refresh doesn't always work, it works about 95% of cases I've seen but I've had to turn it off on a few systems over the years.

ok and i will see what block mode is like what on and off and see which works nest for me

i have noticed any different with byte marge on or off and seem to work fine with it on

maybe this one config that hidden refresh doesn't work

i was also wondering that on the 3rd pic - what dos pci irq activated means and which is better option level or edge

would it matter which one and would they make a different

also wondering - i am aware on pc from penitum era onwards that the graphic card is normally on the top most pci slot but on a 486 is it the same idea or does it not matter which pci slot for dos and windows 3.11

and google is no help much as when type inthe same question and type pci - the most common results is about pci-e (which isnt what i am looking info for) and not just plain pci

PCI IRQ Activated by Edge / Level is the option I was talking about on a different post, that you'd toggle for cards that need their IRQs handled in a particular way. Their manual/documentation would tell you this: 3dfx suggested setting this to Edge for their PCI Voodoo3 cards, for instance.
Generally you only need to change this if a card's documentation so indicates, or if again you're trying to troubleshoot a seemingly flaky card.

Some boards with older BIOSes do get pernicious about the order which you put the cards in, but the better boards tend to work regardless of what slot you put your PCI video card in. To be on the safe side I generally put the video card in one of the first two slots from the right, looking at the board with the processor facing me and the power connector facing the back of the box. Sometimes you'll need to change this order if Windows seems hell-bent on sharing an IRQ with something that it shouldn't, regardless of what you tell it under Device Manager or the CMOS setup.

ok thank you and i am not in voodoo any this build as this is pre real-3d era and i dont see any different with edge/level (that i notice so far but could mess about and see if it does make a different