if i'm not mistaken most nics can have their macs changed by altering the data contained in the tiny 8pin i2c eeprom that's available on most nics.

weedeewee wrote on 2023-01-20, 12:33:

if i'm not mistaken most nics can have their macs changed by altering the data contained in the tiny 8pin i2c eeprom that's available on most nics.

That's true about modern NICs. Original NE2000 cards and early clones used a 16 x 8 parallel PROM (yeah, that's not a mistake for 16K x 8, but really 16 values of 8 bits each!) to contain the station address and the "magic" signature 57 57 in the last two bytes. Possibly it actually is a 32 x 8 PROM like the 74188 or 82S23. This ROM is called "SAPROM" (station address PROM), and can be replaced by custom PROM or PROM-emulators.

RTL8019 ?

Would patching the MAC range check out of the software be an option?

Grzyb wrote on 2023-01-20, 18:02:

RTL8019 ?

Hmm I'd forgotten about those, I wonder if they're truely ne2000 compatible for these purposes. I'll see if I can hunt one down, thank you.

elszgensa wrote on 2023-01-20, 18:25:

Would patching the MAC range check out of the software be an option?

It would, but its a binary blob of an OS2 executable... I assume it to be a modified copy of Microsoft's RPL server in Lanmanager, but I run out of talent in terms of doing anything of that nature.
In terms of testing, I've got the boot rom image successfully working with 86box, but 86box only lets you change the last octets of the mac, not the vendor part. When I asked on the discord about being able to change the vendor part it didn't seem to be something they were interested in facilitating.

Thanks for all the replies so far, lets me explore some more and see if I can make something work.

86box only lets you change the last octets of the mac, not the vendor part

The attached patch should do the trick, saving and letting you load entire MACs. Do note that there's no compatibility fallback for loading old "half-a-MAC" entries, so better use a fresh config.

This isn't very helpful maybe, but I vaguely remember that MAC addresses are still not being repeated/reused/reissued.

The general agreement is that MACs are all different, so that any possible risk of confusion on the internet is prevented.

This includes the earliest NICs ever produced.

Anyway, that's all that does comes to my mind.
Maybe that's why the MAC is tricky to change, also. 🤷‍♂️

I remember back in the old days (P2 and Athlon) some motherboards you could change the built in NIC MAC if you needed, somewhere in my old archives have a few tools for that but not sure where.
It was for us at HP/c for swapping a board and making the MAC the same as the failed board (they always had a sticker to tell the MAC addy,,,), do not think it would work with PCI nics but never know...
Last time I used it was on a Athlon board... yeah been a long time..
But they do exist !

elszgensa wrote on 2023-01-21, 01:46:

86box only lets you change the last octets of the mac, not the vendor part

The attached patch should do the trick, saving and letting you load entire MACs. Do note that there's no compatibility fallback for loading old "half-a-MAC" entries, so better use a fresh config.

Oh wow, thats great thanks.
Now to work out how to build from source 😀 not done that for 86box before...

Jo22 wrote on 2023-01-21, 01:51:

This isn't very helpful maybe, but I vaguely remember that MAC addresses are still not being repeated/reused/reissued. […]
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This isn't very helpful maybe, but I vaguely remember that MAC addresses are still not being repeated/reused/reissued.

The general agreement is that MACs are all different, so that any possible risk of confusion on the internet is prevented.

This includes the earliest NICs ever produced.

Anyway, that's all that does comes to my mind.
Maybe that's why the MAC is tricky to change, also. 🤷‍♂️

Duplicate MACs due to software or user error have been a thing. Repeatedly.

An example I had fun with when working at the helpdesk of an internet provider: take two SiS 900 NICs (either onboard or - rarer - on a PCI card) in separate systems, install Windows XP and let the default drivers in WinXP take control of them. Connect in same LAN - or to the same ISP behind a modem acting as bridge - and let the fun begin 😉

In Windows it's generally possible to manually edit the MAC address in the advanced properties of the adapter (my Realtek 2.5GbE Family has it listed as "Network Address") and in Linux you just add the right flag to ifconfig ("hw ether" iirc).

In fact, this particular functionality is key to why MAC whitelisting in WiFi networks is pointless.

But that's all nice advanced operating systems with real networking stacks and abstraction layers. In DOS, you probably need to mess around with EPROMs.

dionb wrote on 2023-01-22, 02:52:

Duplicate MACs due to software or user error have been a thing. Repeatedly.

That's bad. Isn't there a law that prohibites this? There should be, imho.
Going by logic, modification should be prosecuted civilly and criminally.
Faking a car's licensing plate isn't legal, either, after all.
At least not if the car drives on public streets, I mean.
If it's on private ground (LAN), it's another matter, of course. This won't harm anyone, after all. 😊

Jo22 wrote on 2023-01-22, 09:32:

That's bad. Isn't there a law that prohibites this? There should be, imho. […]
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dionb wrote on 2023-01-22, 02:52:

Duplicate MACs due to software or user error have been a thing. Repeatedly.

That's bad. Isn't there a law that prohibites this? There should be, imho.

At least not if the car drives on public streets, I mean.
If it's on private ground (LAN), it's another matter, of course. This won't harm anyone, after all. 😊

I'm not a laywer, but you should be aware that the MAC address only needs to be unique within a LAN. It's not visible outside that LAN, so we wouldn't get into any technical trouble if my computer uses the same MAC address as your computer, unless we meet up and join the same (possibly wireless) LAN. So in my oppinion, there needs to be no public prosecution, but the possible damage done to companies that got their LAN messed up by duplicate MACs might be interpreted as civil liability against the supplier or manufacturer.

^Thanks for your explanation, makes sense to me. 🙂👍
I also was merely thinking out loud in my previous post.

Isn't there a law that prohibites this?

You bought from the same manufacturer, and then happened to guess the same random three-byte number as me. Straight to jail!

elszgensa wrote on 2023-01-22, 13:22:

Isn't there a law that prohibites this?

You bought from the same manufacturer, and then happened to guess the same random three-byte number as me. Straight to jail!

Yay! Tschakka! 😁

Edit: It's a hexa-nibble! ^^

I've heard a story about some company purchasing a lot of cheap NICs...
when they tried to get them running, it turned out they all have the same MAC 🤣

Ok found the MAC ID tool, it was used on the ECS K7S5A that had SIS900 chip (V3.x) to change MAC addresses. It was in my K7S5A stuff.
So it might work for a PCI NIC with some SiS 900/7016 chip. The exe header says "SiS 900/7016 LAN Adapter EEPROM Utility v1.52"

Grzyb wrote on 2023-01-22, 15:37:

I've heard a story about some company purchasing a lot of cheap NICs...
when they tried to get them running, it turned out they all have the same MAC 🤣

That's probably those SiS900. The drivers from the manufacturer site work fine, those in default XP install point to the wrong memory address where there is some random - and non-unique- code instead of the EPROM where the valid MAC was burnt.

It wasn't the only example, but it was particularly bad as a lot of low-end computers sold by the likes of Aldi (discount supermarket across Europe) shipped with this adapter and the faulty drivers in 2003 and 2004. There used to be a website with a list of known non-unique MAC addresses but I can't find it now.