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memory issue with my 486

J

JDT

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Feb 17, 2007
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Cicero, NY
Bios reports 640K and 64MBs ram, memtest passes fine.
When I boot from the hard drive, I have 625k conventional listed.

I booted my dos 6.22 F5 (ignore autoexec and config.sys) and mem still lists 625k, I remember getting a bug back in the day that took 1k and would say I had 639k of ram... think maybe this could be similar? Whats a good anti-virus for dos?

Now here's a good one. Since I'm using ontrack disk overlay, if I'm booting to a floppy, I need to let the overlay load before I boot the floppy other wise the system may corrupt the disk, but if I boot the overlay, wouldnt a MBR virus boot with it? hmmm

So anyway, suggestions for dos anti virus?

Thanks in advance.
 
First I would unplug the HDD, then boot from a floppy and check the RAM size, if it 640k then you are right there is something on the HDD taking up RAM.

Are you sure its not the HDD overlay that is taking up the RAM? I remember trying several different overlays to find one that took up the least amount of memory. I am not sure which one I ended up using, but I can look it up if you like.
 
lutiana said:
First I would unplug the HDD, then boot from a floppy and check the RAM size, if it 640k then you are right there is something on the HDD taking up RAM.

Are you sure its not the HDD overlay that is taking up the RAM? I remember trying several different overlays to find one that took up the least amount of memory. I am not sure which one I ended up using, but I can look it up if you like.
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No I'm not sure its the overlay, however booting from floppy does result in 640k ram, and booting the overlay first., then floppy results in the 627k.
Re-booting to floppy first again results in 640k, since floppy was present during overlay boot, I can assume perhaps its not an MBR virus as that probably could/would/should infect a floppy if accessed.

I'd be interested to know what overlay you had been using, if you have the info handy.
 
I am using EZ-Bios 9.06M, and my system reports 635k of total RAM, the 5K is used by the overlay.
 
JDT said:
No I'm not sure its the overlay, however booting from floppy does result in 640k ram, and booting the overlay first., then floppy results in the 627k.
Re-booting to floppy first again results in 640k, since floppy was present during overlay boot, I can assume perhaps its not an MBR virus as that probably could/would/should infect a floppy if accessed.

I'd be interested to know what overlay you had been using, if you have the info handy.
Click to expand...
I don't think that's out of the ball park. How are you checking your memory after booting with the HD? What does DOS 'MEM' say? Try running MEMMAKER and see what you get.
 
The drive overlay is memory resident and does take up RAM space. Essentially, it furnishes a replacement INT 13H service. Of course, the issue is how one allocates memory for the overlay before DOS is loaded. The way it's done is to lower the amount of available RAM reported through the BIOS and stick the code into high memory.
 
Chuck(G) said:
The drive overlay is memory resident and does take up RAM space. Essentially, it furnishes a replacement INT 13H service. Of course, the issue is how one allocates memory for the overlay before DOS is loaded. The way it's done is to lower the amount of available RAM reported through the BIOS and stick the code into high memory.
Click to expand...
OK, I better be careful here, before it gets beyond my understanding. :) Anyway, the ANYDRIVE doc would indicate that it stores the drive parameters in the master boot block, claiming that there is extra space there to do that. I haven't had reason to run it for some years, but I don't recall any memory usage. Perhaps I didn't notice.
 
IIRC Anydrive used very little RAM (about 1k), but it was severly limited in the actual size of the drive it can handle, I think it maxed out at 2048 cylinders. So it may not be a solution for you if your drive exceeds this.
 
Thanks guys, switched to EZ-BIOS from the MAXBLAST install, takes up less memory and now I've stopped getting "insufficient conventional memory" errors in ES: Arena =P
 
Ole Juul said:
OK, I better be careful here, before it gets beyond my understanding. :) Anyway, the ANYDRIVE doc would indicate that it stores the drive parameters in the master boot block, claiming that there is extra space there to do that. I haven't had reason to run it for some years, but I don't recall any memory usage. Perhaps I didn't notice.
Click to expand...

Code has to be executed out of memory--it's not just a matter of storing a bunch of parameters--there has to be code that knows what to do with it. The minimum size of memory that can be reserved before the OS is booted is 1K; what the 16K is about, I have no idea, unless there's also some performance stuff there.

It isn't just drive overlays that can use this mechanism. You can write and stick your own debugger code, for instance and spy on an operating system or bootable game in this fashion. SIMCGA did this when dealing with bootable games--loads its own code in high conventional memory; decrease the BIOS-derived amount of memory available, then load the boot sector from the game floppy and pass control to it.
 
check your BIOS if it has an option for remapping the memory used by HDD controllers above the 640k limit:

Hard Disk Type 47 RAM Area:
The BIOS has to place the HD type 47 data somewhere in memory. You can choose between DOS memory or PC BIOS (or peripheral card) memory area 0:300. DOS memory is valuable, you only have 640KB of it. So you should try to use 0:300 memory area instead. There may be some peripheral card which needs this area too (sound card, network card, whatever). So if there are some fancy cards in your PC, check the manuals if they're using the 0:300 area. But in most cases this will work without checking. This is redundant if BIOS is shadowed (maybe not in very old BIOSes). The RAM area can be verified by checking address of int41h and int46h. These are fixed disk parameters blocks. If they point to the BIOS area, BIOS made modification ofparameters before mapping RAM there.
Click to expand...
 
JDT said:
Whats a good anti-virus for dos?
Click to expand...
If you're talking about a bootable one, I use Norton Antivirus Emergency Boot Disk for DOS. PM me with email address and I'll send it.

Now if you want to install one, theres F-prot for DOS (you'll have to find it, they no longer offer it.) Norton AV, Early versions of McAfee, etc.....
 
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