Hi, that's a neat (or nifty) thing you did. Congrats! 😁
While I've got no Compaq Portable III myself, I think this would indeed be useful to any Compaq owner.

Best regards,
Jo22

LeFlash wrote on 2018-09-16, 19:33:

First of all, this machine got an IDE->CF-adapter in the drive bay. Second, a Gotek. But i didn't want to use Ontrack, so i chec […]
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First of all, this machine got an IDE->CF-adapter in the drive bay. Second, a Gotek.
But i didn't want to use Ontrack, so i checked what the 2 empty ROM-sockets are doing.
Turned out they are mapped at E000h. The Bios unfortunately only checks from C000 - DF80h for extension roms.
So i patched the BIOS to scan up to EF80h and removed its CRC-routine to make things easiert. Split XTIDE-Bios in Lo/Hi,
burned and voilá! Works like a charm. 😀

Anyway, if anyone is interested in the patched bios, let me know!

I'm very interested in this if you still have the patched BIOS. I have been restoring a III and would like to have XTIDE on it without using up an ISA slot in my expansion.

LeFlash wrote on 2018-09-16, 19:33:

Anyway, if anyone is interested in the patched bios, let me know!

I'm definitely interested in the patched BIOS, or at least instructions on how to modify my own BIOS. It's always good to spread the knowledge.

I'm also magically interested in this now - I acquired one today for AUD$130 (with an expansion bay and official carry bag) and am extremely happy 😀

I too have an old Compaq III I am trying to upgrade. However I have no success using several different compact flash-to-IDE adapters, as well as several CF cards, with zero success as a disk replacement. Would you please identify what adapter and what CF you used to get this replacement to work? I have run out of ideas.
Many thanks for any help you can provide.

My patched BIOS works by disabling the OEM BIOS CRC-Check and growing the searchwindow for extension ROMs to the area that can be mapped in memory by the two additional sockets. This sockets now get a regular version of XTIDE which works with normal IDE-controllers like the ones in the Compaq P3.

If nothing of this stuff works, you might have a bad ide controller or cable inside your P3.

Have you already swapped all parts?

The usual adapters work well, but you have to use XTIDE or have a corresponding bios setting for your card. (actually, i never tested it without xtide, so maybe the bios is just incompatible with it, but that's rather rare)

Hello,

This patched BIOS also interest me.
Is it for 286 or 386 motherboard?

I’m also interested in more technical details, especially how did you locate the CRC routine and how do you bypassed it!

Many thanks!

Best regards

bwana_fr wrote on 2021-08-28, 16:49:

Is it for 286 or 386 motherboard?

It is for the 286 Compaq III Portable. I am also interested in how you determined what needed to be modified.

I’m definitely interested into this BIOS as I own the 286 version!

kuenzign wrote on 2021-08-28, 22:09:

bwana_fr wrote on 2021-08-28, 16:49:

Is it for 286 or 386 motherboard?

It is for the 286 Compaq III Portable. I am also interested in how you determined what needed to be modified.

Use some tool like IDA, load the binary and analyze the flow. Most of the time, you find something like

mov dx, 80h
mov al, 123
out dx,al

This is where the bios puts out the current post code. When looking trough the official list, you can see what step in the code now takes place.

Hello,

Using POST codes on disassembled code is very clever!

Many thanks for your response!

LeFlash wrote on 2021-08-30, 07:10:

...This is where the bios puts out the current post code. When looking trough the official list, you can see what step in the code now takes place.

LeFlash, can you share some more details on this? Or possibly your patched Compaq ROMs? I'd love to get this going in my Portable III, but assembly is still a bit over my head.

Thanks,

-J

I'm also interested in this patched BIOS.
I have also problems to install a new Harddisk and like to install a SD-IDE adapter or a CF-adapter.

I have made a Font-Fix to the actual ROM for my Compaq Portable III.
It's a Commodore C64 Font instead of the IBM-Regular 8x8 Font.

My main problem is exactly the CRC-routine-check what makes it impossible to install the modified ROM set.
Unfortunately I have no enhanced Assembler skills to do that.
But I'm also interested to get more in to it. 😀

I would be glad if you can send me your ROMs.

Sorry for my poor english and best regards.

X2themax

The checksum-part wasn't that hard to find. Just had to watch the outputs to the debug-port and look for the code for crc check / error. Between both instructions is the checksum-code, which just needs to be disabled.
(Which isn't the best way of dealing with this, normally one could try to repair the checksum, because most of the time it's just some "sum equals zero"-stuff)

Attached you find the needed files. U72/U89 is the patched stock bios, i had to patch it because now it looks in a wider memory […]
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Attached you find the needed files.
U72/U89 is the patched stock bios, i had to patch it because now it looks in a wider memory area for option roms.
The free sockets are located somewhere where the original BIOS won't look.

You need 4 27C256-type eproms
xeven.bin -> U90
xodd.bin -> U73
U72/U89 in the corresponding sockets

Switch jumper E12 facing towards U88 / upwards

Set "no drives" in the BIOS, XTIDE will do the rest.
You could also use a newer XTIDE-revision in U90/U73, but you have to split the file in odd/even (or lo/hi as some would call it)
But the version i used was from 2018 and working fine, so no need to go any newer.

Hi LeFlash,

thank you very much for sharing your BIOS-Files, I will test it soon !

Best regards,
X2themax

Having spent quite a lot of time on the compaq portable III I was gifted a few months ago ...Model 2670
Replaced keyboard cable...cloned hard drive contents (win 3.1) ..(a 214 mb seagate...though only half used Type35 100mb ?)....fitted a new cmos battery and a 1.44mb floppy ..and increased base memory from 1mb to 2
I'm now curious about the possibility of getting XTIDE on it...and that RGB 9 pin dsub.
Mine is a 386 version and sadly I dont have an ISA expansion back-pack.
My options are limited ..
but like the 286 version I do have 2 empty sockets on the mainboard.
I'm happy to dump the contents of the 2 labled chips in the photo if they would be useful ?
I have a few programmers to try but it would be useful to know the rom type so I dont have to peel the stickers.
Has anyone successfully managed XTIDE on this version ?

Now to the RGB socket which I assume is CGA ?
but how to activate this ...
I do have an adapter which _should_ allow me to connect a TV using SCART ...to the RGBi dsub...but nothing so far.
I assume the compaq wont output to plasma screen and external at the same time...but control-alt-less than gets no response.
I am very unfamiliar with this beautiful luggable so please consider me a novice atm.
regards
VS

If these devices weren't such expensive on ebay right now, i'd get one and try to patch the bios the way i did it with the P3.

Thanks for the reply LeFlash..
I'd be happy to try ...ie ...
I can dump the 2 chips contents for upload...and write a couple of eproms with any mods you made.
I assume I would then just swap the original bios chips out for the modified ones ?
or would the new contents we supplementary in that these chips would be additional and be placed in the empty sockets alongside the originals ?
as I said I am a novice here...but happy to try.

Can you tell me what the chip types are for the originals eproms are so as not to damage the labels by peeling them off.
27C128 perhaps ?
rgds
VS

It's not that easy. First of all, you need some eproms in the free sockets and check, where in memory they get mapped. You can use my xtide for this as stated in the post. Then you need to fiddle with the jumpers and some memory editor for checking where the rom sits. Maybe you are lucky and your current bios scans this region automatically then you do not need a patch. Otherwise, when you get the xtide mapped correctly but the bios doesn't start it, the bios needs a patch.