Did you enabled DMA under Win98, is the hdd running in PIO mode ? Nic transfer speed can also be improved by using "auto negociate" (atleast for me) instead of forcing 100MB half or full duplex.

Probably because you're running the NIC on the PCI bus.

Intel even released a new bus called "CSA", before PCIe came out:

http://www.anandtech.com/show/1094/5

Back in the day, many sites emphasized optimizing the MaxMTU, but I think that was more of an issue on dial-up.
http://easymtu.tripod.com/easymtu/

(Alternatively, if you're running some ancient utility that is trying to optimize your MaxMTU the wrong way, that would also kill your network speeds.)

DMA is on, as far as PCI speed a gb Nic needs only 125 MB/s, PCI provide 133 MB/s, yet it I also true no mechanical hard drive can come close to it, but I would expect about 300-400mbs.

If it's not Win9x config (like Sync Data Transfer, swap...) or drivers related you can also check the BIOS for option as PCI Master WS / Delay transaction / latency timer or even the HDD part with block mode or Multi Sector Transfer... and disable all integrated parts that you're not using (like COM/LPT/modem/audio... to free up maximum resources) if not already done.

Ok thanks for clarifying now that you're getting 48 megabits and not 48 megabytes. That is slow. Try to go into device manager, under the network card properties, advanced tab, force set the speed at 1000mbps full duplex.

PCI is 133MB/sec half duplex only.

Is the card sharing an IRQ with the AGP slot perhaps? (I may be wrong and this could be an old wive's tale, but you are not supposed to use the PCI slot immediately after the AGP slot).

Can you post results from the onboard 100mbps lan?

ok well I did have it in that slot next to the AGP card, I didn't want to remove another slot cover, but did so, now to retest, also verified WS 0 and 1 Write is enable ect.

Get TCPOptimizer. It reconfigures various network settings with broadband in mind and helps internet performance a lot for Win9x and XP. Especially 9x.

Though LAN to LAN SMB transfers on 9x just do not go fast. I don't think it can even max out a 100mbps NIC. It's just not an efficient network OS. It also has no support of offload technologies like checksum and large send. I've found that a gigabit NIC gets you just a little bit more throughput than a 100mbps NIC. Of course this also pounds the CPU hard but you look good there with the Athlon XP.

XP is also not great at gigabit SMB transfers. I think the best I've gotten is 50% utilization. Vista and newer really kick up the speed there.

well the biggest reason for this was that my onboard nic has been flaky, randomly dropping, randomly unable to instalize and overall being a pain in my ass. So was at fry's and grabbed a trendnet gigabit nic for 10 bucks, the cheapest 10/100 was 16 so it made sense to me 🤣.

Can you boot another(newer) OS on the same system and see if it works a lot faster? My experience with SMB file transfers over the network to be about 2/3rds the maximum theoretical speed. A single large file goes faster, lots of small files can slow it down.

Is it connected at 100 or 1gb? Do you have a switch between the two systems or just a network cable? I always hook my systems up with just a network cable and use ICS to get internet to my older boxes.

My fastest 98 system is a P3@733 with a 80GB disk and it only does about 30mbps speed at best, or about 3MB/s give or take using an Intel 100/10 card at 100.

a gigabit switch, other speeds are fine

mainbox, AMD 970 chipset gb nic onboard FX6300 with SSD

Opteron 144 Nforce 3 IDE Seagate 7200.10 500gb network transfer from main box :488mb/s
Pentium 4 3.2 875p SATA Seagate 7200.11 250gb network transfer from main box :418mb/s
then the Athlon XP at 48mb/s seems way off 🤣

Perhaps it is time to remove doubts about hardware from the equation.

What sort of transfer speeds do you get with SFTP? Or what if you boot into Linux using a Live CD and transfer a file with SMBClient?

im currently waiting for the machine to finish formating a spare 120gb hard drive I had, I will be installing windows XP onto it to test. I could try lubuntu but im not sure how well it would run.

well gonna try lubuntu live from a thumb drive, as my spare HDD wasn't in use for a reason it seems I forgot. Its got bad sectors, and this time i just tossed it 🤣

I've been messing with a Windows 98SE & K6-3+ 600 machine. A new transfer rate boosting trick I found is to disable interrupt moderation on the NIC. This feature is a CPU usage management setting. By disabling it, the NIC driver will use more CPU time. I saw a boost from 5MB/s to 11MB/s with a Intel Pro/1000 GT.