Book 8088 discovery and modification thread

[Betamax80]

@Betamax80 I am not closely familiar with the PicoMEM board.
Are you not seeing any PicoMEM BIOS output at all? Or you can't boot from it?

The 8088 BIOS searches the upper memory (D0000-F8000) for BIOS extensions in ascending order.
It might be possible that if you swap the addresses of XUB and PicoMEM BIOS extensions, you'll change the boot behavior, or at least the card initialization order.

Unfortunately, on pre-PnP systems, combining multiple bootable BIOS extensions doesn't always work. It really depends on the implementation of the particular BIOS extension.
For example, in most cases, bootable BIOS extensions will redirect the INT 19h (IPL - initial program loader) to themselves. So that, they can boot the system using the storage/network devices that they support.
Of course, there's only one INT 19h vector, so only one piece of code will get to handle it...
Depending on the implementation of that piece of code, it might boot from its own device right away, or offer some kind of mechanism to boot from other devices, which is done by saving the previous INT 19h vector, and calling that...
XUB, if I am not mistaken, completely replaces INT 19h with its own code, that offers boot from an HDD or a CF card, floppy drives, and serial port (if compiled/configured).
Same problem exists with INT 13h - disk services. But here, BIOSes typically will try to chain the interrupt call, that is if the particular disk number is not serviced by the given BIOS extension, it will be passed down the chain to the next (previous) INT 13h handler...

I suppose that for testing purposes, the ideal would be n0p's BIOS, with loading of extensions allowed but without XUB built into the flash file?
Unfortunately FreddyV has not yet released source to the ROM extension, and I maybe wrong but I don't see any hints.... it may well be that XTIDE is interfering with that PicoMEM is wanting to do.
The Github is here but all are binaries, I think. https://github.com/FreddyVRetro/ISA-PicoMEM/tree/main

 

[sergey]

I suppose that for testing purposes, the ideal would be n0p's BIOS, with loading of extensions allowed but without XUB built into the flash file?

You can try that. But in this case, obviously, you won't have the CF card support.

 

[Betamax80]

@Betamax80 I am not closely familiar with the PicoMEM board.
Are you not seeing any PicoMEM BIOS output at all? Or you can't boot from it?

The 8088 BIOS searches the upper memory (D0000-F8000) for BIOS extensions in ascending order.
It might be possible that if you swap the addresses of XUB and PicoMEM BIOS extensions, you'll change the boot behavior, or at least the card initialization order.

Unfortunately, on pre-PnP systems, combining multiple bootable BIOS extensions doesn't always work. It really depends on the implementation of the particular BIOS extension.
For example, in most cases, bootable BIOS extensions will redirect the INT 19h (IPL - initial program loader) to themselves. So that, they can boot the system using the storage/network devices that they support.
Of course, there's only one INT 19h vector, so only one piece of code will get to handle it...
Depending on the implementation of that piece of code, it might boot from its own device right away, or offer some kind of mechanism to boot from other devices, which is done by saving the previous INT 19h vector, and calling that...
XUB, if I am not mistaken, completely replaces INT 19h with its own code, that offers boot from an HDD or a CF card, floppy drives, and serial port (if compiled/configured).
Same problem exists with INT 13h - disk services. But here, BIOSes typically will try to chain the interrupt call, that is if the particular disk number is not serviced by the given BIOS extension, it will be passed down the chain to the next (previous) INT 13h handler...

@sergey I'm getting a type of boostrap from the picomem - it basically confirms the build of the ROM, then on the same line it goes "init... end" - kind of like its unpacking its main interface but then not displaying it. There is supposed to be an interactive mode which goes to a whole settings menu, basically looking like a machine BIOS, but this does not load (or is getting immediately overwritten by XUB which loads in the next ROM address space).

I'll try to get some screenshots of the behaviour.

There are 2 builds of the PicoMEM ROM - with start addresses of C8 or D0 - I've tried both and only the C8 variant displays the bootstrap.

 

[jscipione]

After plugging the ISA expansion board into my Book 8088 v1 I've managed to break it and it won't boot up anymore. I'm guessing I must have plugged something in backwards and damaged something on the board. Adrian Black's recent video on the Book 8088 (

) inspired me to give repairing this thing a try. I got the board out of its case (ripping the audio connector pads off in the process) but so far I've had no luck troubleshooting the board. All I get is alternating flashing "red" LEDs, no boot sound. When the screen is plugged in it gets power but all I see is "No video signal" so it appears as though the board isn't running

There's no obvious visual damage that would give a clue and none of the ICs are getting hot. The battery seems to hold a charge and powers the board but no boot. I tried replacing the v20 with an 8088 and replacing the BIOS but no luck. I checked the UM82C88-10 IC that was giving Adrien trouble with his machine but mine appears fine and I don't know how to test the chip further and don't have a replacement chip. I tried unplugging and replugging it from the socket but no luck with that either. I see that earlier on page 4 of this thread (https://forum.vcfed.org/index.php?t...-and-modification-thread.1245155/post-1346664) that n0p said "Ok, i fixed the Book with replacing SN74HC245D chip" so perhaps that chip is the problem? Since they are soldered on it's not easy to check.

Any advice on how I might figure out what's gone wrong?

 

[Riccardo]

Hi guys. Just a question: did anybody manage to buy this adapter for the Book8088? Apparently it's sold out. Maybe it's possible to re-create it in KiCad and make it available (e.g. via PCBWay or github)? I don't have a blank PCB to attempt that myself...

But most importantly: does it allow the Book8088 v2 to run on an Intel 8088? Thanks.

 

[jscipione]

I didn't know that existed. It appears to allow a Book8088 v2 to run a CGA card instead of VGA restoring the video card to CGA like on the v1 version. You can run an Intel 8088 on a Book 8088 already. Even if you did recreate the PCB that tough part is reproducing the 2 large ASICs that implement CGA. The same two ASICs are present on the Book 8088 v1 along with a third that implements the XT chipset.

 

[Riccardo]

I didn't know that existed. It appears to allow a Book8088 v2 to run a CGA card instead of VGA restoring the video card to CGA like on the v1 version. You can run an Intel 8088 on a Book 8088 already. Even if you did recreate the PCB that tough part is reproducing the 2 large ASICs that implement CGA. The same two ASICs are present on the Book 8088 v1 along with a third that implements the XT chipset.

Unfortunately, I was unsuccessful running the Book8088 on an Intel 8088 (or clone) - I own a Book8088 v2. From what I understood, the VGA BIOS uses pusha/popa instructions somewhere and, as these are 80186 instructions, it crashes the 8088 (but not the V20).

Returning to my original question: I guess the two ASICs can be taken from other cards on Aliexpress that use the same 6845 combination. Even the part numbers seem identical.

 

[jscipione]

I wasn't aware that the VGA BIOS they're using required a V20, sorry to mislead. That card would enable you to use an Intel 8088 using CGA I suppose if you could get your hands on one.

Yes the two ASICs are most likely the same as the ones used on the Book 8088 v1 and the standalone CGA card.

 

[jscipione]

This guy put a regular (ok soviet clone) 8088 in his Book v2 and it booted up and worked with some software, but it did appear to crash when he ran checkit and other software so that's probably caused by the VGA BIOS incompatibility you're talking about.

 

[Riccardo]

I wasn't aware that the VGA BIOS they're using required a V20, sorry to mislead. That card would enable you to use an Intel 8088 using CGA I suppose if you could get your hands on one.

Yes the two ASICs are most likely the same as the ones used on the Book 8088 v1 and the standalone CGA card.

I guess the card is a good workaround to the lack of Intel 8088 support in the Book 8088 V2. I tried to contact DZT's Store for one, but he seems to be out of them.

This guy put a regular (ok soviet clone) 8088 in his Book v2 and it booted up and worked with some software, but it did appear to crash when he ran checkit and other software so that's probably caused by the VGA BIOS incompatibility you're talking about.

I own the KM180VM88 and the KR1810VM88 too (the former is the military, ceramic version and the latter is the plastic version) and I was unable to boot the machine with either. I then tried a bunch of other 8088s and the result was the same. The K1810VM88 is a pretty reliable clone, it could be that it is an exact clone. Mine were made quite recently in the Kvazar factory in Kiev.

I guess the difference between my machine and this guy's machine (the guy on youtube) is probably the VGA bios. It could be, as he bought the computer after I did, that he got a machine with the VGA bios "fixed" so to run on an 8088.

Ideas anyone?

 

[sorphin]

Hi guys. Just a question: did anybody manage to buy this adapter for the Book8088? Apparently it's sold out. Maybe it's possible to re-create it in KiCad and make it available (e.g. via PCBWay or github)? I don't have a blank PCB to attempt that myself...

But most importantly: does it allow the Book8088 v2 to run on an Intel 8088? Thanks.

View attachment 1278468

I have 2 of them, and 2 of the vgas, you had the option on the v2 to select which you wanted, i bought one v2 with cga and one with vga, and then one spare of each card. you could also use an external vga card if you really wanted "8088" usable vga (since their bios uses 80186+ instructions (hence the V20)). and yes, those are the same CPLDs that are used in the V1 and the 'standalone CGA card'.

 

[sorphin]

I guess the difference between my machine and this guy's machine (the guy on youtube) is probably the VGA bios. It could be, as he bought the computer after I did, that he got a machine with the VGA bios "fixed" so to run on an 8088.

Ideas anyone?

they haven't been changing the VGA card bios, they've been changing the firmware on the micro on the LCD interface board (different thing)...

 

[Riccardo]

I have 2 of them, and 2 of the vgas, you had the option on the v2 to select which you wanted, i bought one v2 with cga and one with vga, and then one spare of each card. you could also use an external vga card if you really wanted "8088" usable vga (since their bios uses 80186+ instructions (hence the V20)). and yes, those are the same CPLDs that are used in the V1 and the 'standalone CGA card'.

Unfortunately, when I ordered mine that option wasn't available. If you decide to sell a CGA card, let me know...