Here's what's going on with my xi8088.

https://www.youtube.com/watch?v=JQBsQMb7p6Y&feature=youtu.be

The machine seems completely usable other than the occasional loud and extended beeping.

I've no idea what's up.

Also, what is C54 for? It's the adjustable trimmer capacitor.

Well good news for me.

This bizarre beeping seems to be directly related to my XT-IDE compact flash board from LoTech; when I boot from it, the beeping intermittently occurs. when booting solely from floppy disk (CF adapter installed but not accessing hard drive) everything seems to be fine; I ran through a BASIC loop as a sort of burn-in for an hour or so without any issue.

Maybe it's DR-DOS causing the beeping, I should eliminate that possibility as well.

So something in the XT-IDE universal bios appears to trigger this issue; I manually updated the version in my 8088 bios to the latest... 580? build, I believe.

Still no idea what C54 is for. Looks like it is tied to ISA bus timings or something? Something to do with that 14.138mhz oscillator, anyway.

C54 is used to adjust the crystal's series capacitance load. The parameters of the crystal are specified for a given series load, usually between 10 and 20pF. The exact crystal linked from the BOM asks for a series load of 10pF. The circuit, PCB etc will add some stray series or parallel capacitance, so the exact load you will have to add may be lower or higher than that to obtain the exact frequency that the schematic asks for. See for instance http://home.kpn.nl/dpasop/pdfs/circuits.pdf fig.11

That's interesting. I have no idea how I'd calibrate that. I don't have any idea what the current capacitance is on that, in fact.

keenerb wrote:

That's interesting. I have no idea how I'd calibrate that. I don't have any idea what the current capacitance is on that, in fact.

With an oscilloscope, or a precision frequency meter. Basically you want to have the oscillator run at its specified frequency. That's 14.31818MHz, or a cycle period of 6.98412e-8 seconds. 😀

WHELP... I guess I'll just have to hope it's right...

I'd probably just set the trimmer empirically for about 10pF, which should be around 1/5 to 1/4 turn from the extreme left position.

OK so I have EVERYTHING together, including my ISA backplane (and upgraded to 32mhz oscillator for my 10mhz V20).

The beeping is recurring. It's NOT just the xt-ide board; two 8-bit VGA cards cause similar behaviour during post, but it goes away as soon as the floppy boot starts. The POST code where this begins is currently happening directly at "10", which appears to be

e_kbd_ok equ 10h ; KBD test passed

in the bios code...

*edit*

I'm really starting to wonder if this is just a bug in the bios. It happens EVERY TIME I restartthe computer, at bios step 10, and ends at (or before) post code 12.

HOWEVER, if I ctrl-alt-delete the system it starts but never stops.

I think maybe the speaker is being turned on at some point but not being turned back off, and then certain types of activity is causing the beeping.

I can duplicate this now 100% under various circumstances. Still no idea what's up.

The beeping occurs during the video card bios initialization and stops at port 80 post code 12, which is when RTC initialization happens.

I do notice that Sergey's port map has various i/o ranges aliased to the pc speaker address that don't seem standard. I/O port 63h, for example...

http://www.malinov.com/Home/sergeys-projects/ … 088#I/OPortsMap

compared to

http://bochs.sourceforge.net/techspec/PORTS.LST

Any idea if that might cause a problem?

the port map difference is because xi8088 is an XT but has an AT keyboard chip, the AT keyboard chip uses those port addresses, so you dont get the XT PPI stuff.

just ordered the parts to do the xt cf lite card.

I wonder if your beeping is related to shorting your speaker? maybe one of the 74 series chips or something. i wonder if there is a direct line from the speaker to any of the logic chips, so rather than doing a filter/comparison anything within the speaker address range on the bus is going through.

looking on schematic, if you have a spare 74F244 (U23) 74ALS74 (U33), 74ALS175 (U26), 74ALS00 (U45)

U45 is directly inline with the speaker... I would try U45 change first, then do U23 + U33 + U26.

I picked up a programmer that has logic testing and all the 74 series chips passed multiple runs.

Doesn't mean there isn't an issue but they test ok. I had already replaced those particular chips anyway.

What video card are you using on yours? Mine is fine with an EGA/CGA/MDA, but all three VGA cards cause the problem but only during VGA/EGA bios initilization.

It also has no issues booting just from floppy, with the XT-IDE card uninstalled.

It's also always 400 Hz tones, despite what other sounds might have been played at the time. For example, during Champions of Krynn, the beep has occasionally happened during music/gameplay sounds, and is still at 400 Hz, which make me think that there's an explicit bit of code somewhere that's setting the sound timer to that frequency.
All pc speaker sounds would tinker with timer 2, right?

Sergey's bios appears to specify a 400hz tone for two reasons: CPU failure and low memory error, in bios.asm. Both of those appear to only fire during power on self-testing, and neither should be setting a timer to 400hz unless there's a "failure" condition?

Since the XT-IDE card causes this problem pretty regularly, I might go in to the source and start spamming debug output to the post card that's built into the malinov backplane and see if anything pops up...

Now that I have a proper PSU + case, I did some playing around and Ive noticed that the VGA card I have, will not often initialise on bootup. I have to hit reset button a couple of times, so there is some timing issue I believe 😒 it is worse witth turbo enabled.

maybe something else is going on with my board tho, with turbo on, I cant hit F1 and get into the bios setup, with turbo off, I can. my turbo is 32mhz so thats 10.something so maybe I should clock it back to 8mhz on turbo.

I should be able to do my CF card this week (finally!) and I still need to drill out the ISA bracket so I can properly mount the board into the case.

I'm running mine with 32mhz crystal as well now, my only issue is the beeping. I haven't figured out how important that adjustable capacitor is, maybe you should look into that.

I am at the point where I"m considering ordering a new board + sockets and transferring my logic over, this beeping issue is driving me nuts and Sergey hasn't replied to an email for over two weeks, I think maybe I made him mad. 🙁

Or he's on vacation/busy, it is summer after all.

keenerb wrote:

I haven't figured out how important that adjustable capacitor is, maybe you should look into that.

I could do it, its a shame there is no test point for measuring it easily. I have rubidium standards for my frequency counters and such, so I can do a very accurate measurement of the crystal, but a proper test point would be nice! There are two vias or empty through holes that might be test points near the pot, I need to check.

looking on the datasheet for the 82c84 at U1.

OSCILLATOR OUTPUT: OSC is the output of the in external oscillator circuitry. Its frequency is equal to that of the crystal.

PROCESSOR CLOCK: CLK is the clock output us ed by the processor and all devices which directly connect to the processor’s local bus. CLK has an output frequency which is 1/3 of the crystal or EFI input frequency and a 1/3 duty cycle

so my plan, measure the OSC pin 12, on U1 and trim the pot to exactly 14.31818MHz

I'm wondering if I dont need to play with the wait state dip switch on the board too.

I need to look at BIOS source, I have the specified RTC/NVRAM but if you enter 2016 date, it looks good, on reboot it comes up as FF16-07-20 date. hmmm...

I switched from a 12C887 (not on the "official" support list) to a 12885 and installed the battery and 32768 crystal. No change to my board's behaviour, I'll check the date/time when I get back home.

I have not seen any change from wait state dip switches, one through four all seem to work fine at 10mhz for me? I'm only really using Ultima IV's attract mode as any sort of benchmark though.

keenerb wrote:

I'm running mine with 32mhz crystal as well now, my only issue is the beeping. I haven't figured out how important that adjustable capacitor is, maybe you should look into that.

I am at the point where I"m considering ordering a new board + sockets and transferring my logic over, this beeping issue is driving me nuts and Sergey hasn't replied to an email for over two weeks, I think maybe I made him mad. 🙁

Or he's on vacation/busy, it is summer after all.

Stop-band 400Hz filter between PCB and speaker? :p

stamasd wrote:

keenerb wrote:

I'm running mine with 32mhz crystal as well now, my only issue is the beeping. I haven't figured out how important that adjustable capacitor is, maybe you should look into that.

I am at the point where I"m considering ordering a new board + sockets and transferring my logic over, this beeping issue is driving me nuts and Sergey hasn't replied to an email for over two weeks, I think maybe I made him mad. 🙁

Or he's on vacation/busy, it is summer after all.

Stop-band 400Hz filter between PCB and speaker? :p

😁 maybe! It's really only a matter of principle at this point, it works fine with the hardware setup I intend to use (two 3.5" drives + ega card), but it irritates me that I couldn't use VGA if I wanted to. Even though I don't plan to.

Sergey replied to me, he has been on vacation but he mentioned that one possibility for my beeping is that the system memory is unbuffered and could potentially cause noise/tones if the ISA bus is under high load.

I have previously assembled a lo-tech 1mb memory card which claims to be "buffered via a 74HCT245" so I'll see if that can be substituted for the on-board RAM.

Ive got my frequency counter on the OSC pin I believe, going to let it run a while so the oscillator oven can warm up but off the bat we are reading a steady 14.3180540... once its warm I'll see if I can get it to 14.31818. right now its slowly ticking down as the oven in the counter warms up and stabilises.