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Any good tool to inspect unusable upper memory blocks?

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First post, by LSS10999

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I modded my motherboard's BIOS to include Plop Boot Manager as a LAN PXE ROM. While it works great, I noticed an undesirable side effect: About 40KB of upper memory is no longer available.

If I disable the boot manager (by disabling PXE ROM from BIOS), those "missing" upper memory area would be usable again, which means the boot manager is permanently resident in the upper memory area and not released after booting into a partition.

I wonder if there is a good tool to do an in-depth conventional/upper memory inspection so as to know where the "option ROM" resided, and then I can test if it's possible to safely reuse that part of upper memory (using I=xxxx-xxxx option) as the boot manager itself is no longer useful now that I've booted into DOS.

If not, guess I'll have to use a different means to invoke such boot managers, as upper memory area is too precious to be wasted by option ROMs.

Reply 1 of 4, by rmay635703

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A member did have a utility that would inspect and clear any available memory above 640k providing a map.

I can’t remember who or how long ago I saw it as I would have used for it on my 1000rlx

Viewing the Upper Memory area

https://youtu.be/Xcc_D7q9bQs

Reply 3 of 4, by LSS10999

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Okay, just checked the threads you referred to. Don't know if MSD can work with other DOSes like FreeDOS. Do I need to load a memory manager before running MSD or CheckIt?

I remembered having tried another tool called DOS6MM that could show some simple information about available memory ranges, but cannot really tell what exactly was taking up the area, and must be run without a memory manager for best results.

Not to mention some memory area can be... "sensitive". I mean that any accesses to it, even just poking around, would cause the system to freeze/hang. MEMMAKER from DOS 6.22 had a mention about the HIGHSCAN option, but it never worked for me even on very old systems. All it did was to cause a freeze requiring a hard reset. Had anyone managed to safely salvage any area from the F000-FFFF range? Back then I did manage to include up to F000-F1FF on a system without outright crashing it, but the system was unstable as games may crash/freeze halfway... Should note that DOS6MM would simply mark the entire F000-FFFF range as reserved without actually looking into it, possibly due to the risk of crashing the system.

Guess I have no choice but to refrain from using Plop as PXE ROM for the system that I intend to use DOS on, as I would not have enough UMB area to enable EMS that way. Without EMS, the system in question has only about 105KB of available upper memory including the B000-B7FF area. From what I've tried, GRUB4DOS can already do more than what Plop could offer, and can be booted in many different ways.

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