It is always advisable to mirror the binary to fill entire memory chip. You can set the ROM window to 8, 16 or 32KB in 3COM config utility and choose appropriate location in the memory map.

Usually filling the chip is not necessary - it can even stay at random state. The software you program, would never point to outside of itself.

Of course, you can play tricks if you want, but... i don't think that's the case.

The beginning/entry point must be in correct position though...

EDIT: Seeing Tiido's post, i would trust him more than myself 😀

Hi! I got negative result with compatibility W27E512-70 and 3COM 3C509B-C .

I programed the W27E512-70 with the BIOS (version BETA 2.0.0.3+). This picture was taken when I read the chip to verify.

The chip was plugged in the 3COM boot socket:

But the 3com configuration program always give me the following error:

Obviously I've tested all base address with the same error.

I think it's not compatible that Windbond with 3com

I suggest you to use the 8KB version and "repeat-copy" it all along the 64KB of your rom to test the compatibility. You can do it with 12KB verison too AFAIK but I really have no idea how can I convert an 12KB ROM image to an 16KB one, I couldn't test it myself. "Repeat-copy" works with regular ROM sizes, like 8,16,32, etc.

I'm suggesting that because I was getting the same message while using 12KB verison in some 64KB EPROMS, and having filled the entire ROM with the 8KB version solved the problem.

Since I'd rather use the 12KB version, I'm actually using a 16KB EPROM (27C128 if I remember correctly), not a compatible EEPROM though (yes, I have a EPROM eraser).

PS: copy/b oldrom+oldrom+oldrom+...+old.rom new.rom

I cannot confirm, have it running on a 3C509B-C (mine looks slighlty different) and a W27E512. I also remembered to have difficulties with the 12kb and used the 8kb. Its a good point to start. However, the card-Setup shouldnt care about it. Check your memory, do you have emm386 running or BIOS-shadowing? Turn both off....

I have the feeling that 3C509B isn't compatible with 512 chips . IIRC it supports up to 27C256 .

< not needed >

--> Works

Hi again!!
First , thanks a everyone to respond.
I think there is a problem with these "bigger" chips. Predator took some pictures with his 3com card, but my 3com has physical layout different from him. His card works properly, the mine not.

The BIOS that previously I used was ide_atl.bin release R598 (beta 2.0.0.3+). I already created a new modified BIOS from ide_atl.bin. The size of the initial file is 9102 bytes. With the utility from my EPROM programmer I've copied the BIOS in other position inside of the memory: $4000 (16K), $8000 (32K) and $C000 (48k) and I wrote in the chip. I haven't got any more free time today, but this weekend I'm going to finish the work and do extra tests.

As said, dont think its ROM content but your memory configuration. ROM content is not checked by the card.

Not sure if this will help but, a friend of mine also had issues getting the V2.00 beta3 BIOS revision to work on his NIC.
After burning a V2.00 beta2 BIOS revision, it worked fine.

Hm i also have latest XTIDE on 3Com but it just would go for a 27C64 ROM.
I don't want to waste Memory 😉
And it just works.
A Bigger ROM was troublesome for me and is wasting Upper Memory Blocks..

Also found out that 2764 ROMs don*t work.. 🙁 and i have plenty of them 😳

This weekend, at some point, I'm going to be trying a similar exercise with a 3C509 and a ide_386l image.
I definitely don't have any 27C128's "in stock", and I'll probably end up using 27C512, because I have more of them available.

My game plan is to
1) Pad out the image from 10240 to 16384 bytes with zeros.
2) Fill the EPROM with N times 16k images, so I'll either have a 27C256 with two identical 16k images, or a 27C512 with 4 identical images, and burn the eprom
3) When I reconfigure the card, I will set the window size to 16384bytes. (This is important - the Option ROM window size is driven by the size of the image, not the size of the device)

Step 1 is to allow step 2 to work
Step 2 is so that I don't need to care how the A14 and A15 pins are handled.
Step 3 is to that I only expose one instance of the EPROM contents to the memory map.

I'll come back with the results, which may be heavily dependent on whether my Dell 486P plays ball or not - the VGA connector or the lead seems to be a bit mechanically flakey.

The aim of the game is to get a 4.3Gb spinning rust IDE drive working in a PC which suffers from the 504/528Mb drive limitation.

It is always advisable to pull up or ground unconnected input pins, in this case the excess address pins. 10K resistors should be sufficient.
If they are left dangling, this may lead to glitches when reading the contents.
In case you fixate the inputs of the excess address pins correctly, either by pullup or pulldown, there is no need to duplicate the PROM contents.
The PROM test failure might be an indicator of that. At the first glimpse the PROM appears to work (see the 55 AA signature). But there are read errors leading to checksum fail. Either through the glitches I mentioned or by a flawed source file which does not checksum correctly.

matze79 wrote:

Hm i also have latest XTIDE on 3Com but it just would go for a 27C64 ROM. I don't want to waste Memory ;) And it just works. A […]
Show full quote

Hm i also have latest XTIDE on 3Com but it just would go for a 27C64 ROM.
I don't want to waste Memory 😉
And it just works.
A Bigger ROM was troublesome for me and is wasting Upper Memory Blocks..

Also found out that 2764 ROMs don*t work.. 🙁 and i have plenty of them 😳

Not sure if it works for you, but..
Re: IDE disk-on-module + 386
😀

Sorry, but most hints here will not solve the issue. The NIC doesent check the ROM content. The error message say that it cannot find a free ROM-space. Thats the only problem.

So either clear up your memory or your card is damaged (whcih is rather unlikely when you take a look at mine which is still running)

After a lot of testing... I've found the problem.

The XTIDE BIOS I downloaded it came from two differents sites:

http://www.xtideuniversalbios.org/binaries/ (ONE)

and

https://code.google.com/archive/p/xtideuniver … lbios/downloads

All the BIOSs I burnt in the 512 kb Winbond from site ONE doesn't work properly (version 588, 598...) and the NIC gave the message I wrote before

If BIOS from the other site (version BETA 1/2/3) burns in the Windbond, it works properly

Now I have another problem.

I would like to use a mechanical Hard disk (no SSD) with my older motherboards (286, 386). As you know actually there is not available mechanical IDE Hard disk. I thought in SATA HD with SATA to IDE adapter. it works properly in my Pentium motherboards with integrated IDE controllers, but if the motherboard has not IDE controller and I have to plug a multi io+ ide doesn't works properly.

The hard disk is availabe in the fdisk DOS command, but I do some partition, when the computer resets to proceed with the format of the new partitions , there is no partitions: the table of parttions is never saved ¿¿??

Has something similar happened to someone?

Short version:

I got my XT-IDE BIOS working in a 27256 filled with 2x16k images, installed in a 3C509B.

Long version:

OK, here's what I've learned so far.
I have a 3C509B-Combo - the important thing here is that I have a 3C509B not an older 3C509.
I have an old Atmel 27C256R (120ns) EPROM - 32Kx8
The aim of the game was to use XT-IDE to allow me to access a 4.3Gb "mechanical" disc drive.

I also got my hands on the "Etherlink III Parallel Tasking ISA, (blah blah) Adapter Drivers Technical Reference"
available at https://www.janwagemakers.be/PIC18F452_3COM_3 … rnet/3c5x9b.pdf

From the Technical Reference document (and informed by 2764, 27128, 27256 datasheets) I found out the following:

3C509B
Supports all 28 pin ROMs - 2764, 27128, 27256, 27512 (No need for modified EPROMs or NICs)
Can be configured to use "8k, 16k, 32k and 64k" ROMs
If you select a 32k or 64k device, the device has a 16k UMA window, and the NIC uses a "ROM Option" register to allow bank switching in that window.
This means that the A14 and A15 pins on the ROM socket are driven, and are not floating.

3C509
Does not explicitly support 27512
Supports all other 28 pin ROMs - 2764, 27128, 27256
Can be configured to use "8k, 16k, 32k" ROMs
If you select a 32k device, you get a 32k UMA window, which means A14 is determined by the ISA bus, and the whole device is exposed.
It is possible that for 8k and 16k modes the A14 pin (pin 27) is tied to Vcc (this pin is "not program enable" which is usually set to Vcc for read operations)
It is highly likely that the A15 pin (pin 1) is tied to Vcc (this pin is Vpp which is usually set to Vcc for read operations)

From practical experience
If you use an old configuration program, you can only select 8, 16 or 32k devices.
If you use an old configuration program on a 509B, chosing 32k device will result in a 16k window as per the hardware design.

If you do not have a ROM installed in the NIC, the configuration program will give the warning message that others have seen.
(Hint: The program probably looks for the 55 AA signature at the ROM base address, and nothing else)

I did the following:

Target PC configuration
* Installed the 3C509B with no OM onboard
* Booted the system with an old MS-DOS hard drive (540Mb) and ran 3C5X9CFG to select 16k ROM at C8000H
Got the warning message, went ahead anyway.

XTIDE image preparation
* Copied IDE_386L.BIN and XTIDECFG.COM to an MSDOS virtual machine. This created a new IDE_386L.BIN which was 10k in size.
* Copied the new IDE_386L.BIN file to my Linux box, padded it out to 16k (dd if=/dev/zero bs=1 count=6144 >> IDE_386L.BIN )
* I then created a 32k image file (cat IDE_386L.BIN IDE_386L.BIN > IDE_386L_27256.BIN
* I then loaded this into my EPROM programmer and burnt the EPROM.

Testing the EPROM
* Powered off the 486
* Inserted the EPROM in the card
* Got the expected output from the new BIOS extension and Successfully booted off the 540Mb
* If I have any problems from this point, it's down to XT-IDE.

So, to end:
The 3C509B drives the EPROM A14 and A15 lines, no need to modify EPROM or card.
The 3C509 is a little less clear - in 32k mode, A14 gets driven. In other modes, A14 probably gets forced to +5v, and A15 is probably tied permanently to +5v, but it will need to be tested.

For 3C509 and 3C509B, pad out your image to 16k, and duplicate the image to fill the device.
For 3C509B you can use 27256 or 27512 - and you can either select 16k or set the actual device size.
For 3C509 stick to 2764 or 27128 unless you want to do some testing and use a 27256 or 27512 after selecting 16k device.

If you duplicate the image, and you know that the A14/A15 lines are being driven high or low, you can be certain that whatever the card does to the pins, you will always
get a 16k BIOS extension made available to the ISA bus, and you don't need to concern yourself whether each pin is high or low.