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Xi 8088 by Segey Kiselev

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Reply 440 of 614, by Sir Isaac

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Are there alot of diy ISA cards floating around?
I found these awhile back.
https://www.lo-tech.co.uk/product-category/retro-ibm-pc/

Unfortunately they never seem to be in stock.

I'm going to roll some of my own soon, possibly in the new year.

Reply 443 of 614, by smbaker

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I ordered myself the 1MB conventional and 2MB EMS PCBs from texelec this week, as well as all the parts to complete them from digikey. I don't really have a need for the 1MB board at this time, but it seems to be a useful thing to grab while they're available, and will provide a useful datapoint on Xi 8088 compatibility. I think keenerb had compatibility issues with his; will be interesting to see if I run into the same thing he did.

Sir Isaac, you asked me earlier if I've resolved my stability issues. Sorry for not getting back to you. I haven't had any further luck. I'd say my build is "mostly stable" but not "completely stable". Seems to have more issues with the second SRAM chip than the first when running checkit.

Reply 444 of 614, by keenerb

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smbaker wrote:

I ordered myself the 1MB conventional and 2MB EMS PCBs from texelec this week, as well as all the parts to complete them from digikey. I don't really have a need for the 1MB board at this time, but it seems to be a useful thing to grab while they're available, and will provide a useful datapoint on Xi 8088 compatibility. I think keenerb had compatibility issues with his; will be interesting to see if I run into the same thing he did.

Sir Isaac, you asked me earlier if I've resolved my stability issues. Sorry for not getting back to you. I haven't had any further luck. I'd say my build is "mostly stable" but not "completely stable". Seems to have more issues with the second SRAM chip than the first when running checkit.

No memory expansion boards worked with my xi8088. I didn't try an EMS board.

Reply 445 of 614, by Sir Isaac

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smbaker wrote:

I ordered myself the 1MB conventional and 2MB EMS PCBs from texelec this week, as well as all the parts to complete them from digikey. I don't really have a need for the 1MB board at this time, but it seems to be a useful thing to grab while they're available, and will provide a useful datapoint on Xi 8088 compatibility. I think keenerb had compatibility issues with his; will be interesting to see if I run into the same thing he did.

Sir Isaac, you asked me earlier if I've resolved my stability issues. Sorry for not getting back to you. I haven't had any further luck. I'd say my build is "mostly stable" but not "completely stable". Seems to have more issues with the second SRAM chip than the first when running checkit.

Hey, thanks for getting back to me, really appreciate it. Your videos are great, keep them going when you have time.
I too have ordered the 2MB EMS board from texelec. Hopefully in a few weeks I can play around with it. It will give me a chance to use my new solder re-flow oven 😀
Also I ordered the Lo-tech ISA XT CF Adapter rev. 2b pcb. Going to see if can get an actual HDD working with the system using it. I'd like to try out a cf card master slave setup as well.
That's great you have the stability issues some what under control. I was preparing to build something like your bus terminator board in case I had issues but, maybe I don't need it.

So far I have built the back-plain, CPU board, and OPL2 board. Today I'm working on the floppy / uart board and possibly the vga card. Within the next week I should have the cf board done as well. Somehow I ordered the wrong cf card socket for it.
To date, everything is working great. I get a score of 94.7 in 3dbench2. In checkit all tests complete without errors except the dma & rtc tests. I'm assuming these tests are searching the wrong addresses for these devices?

Last edited by Sir Isaac on 2017-10-18, 18:27. Edited 5 times in total.

Reply 446 of 614, by Sir Isaac

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keenerb wrote:
smbaker wrote:

I ordered myself the 1MB conventional and 2MB EMS PCBs from texelec this week, as well as all the parts to complete them from digikey. I don't really have a need for the 1MB board at this time, but it seems to be a useful thing to grab while they're available, and will provide a useful datapoint on Xi 8088 compatibility. I think keenerb had compatibility issues with his; will be interesting to see if I run into the same thing he did.

Sir Isaac, you asked me earlier if I've resolved my stability issues. Sorry for not getting back to you. I haven't had any further luck. I'd say my build is "mostly stable" but not "completely stable". Seems to have more issues with the second SRAM chip than the first when running checkit.

No memory expansion boards worked with my xi8088. I didn't try an EMS board.

Did you try loading any UHM or EMS memory drivers?

Reply 447 of 614, by widgetii

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Hello, guys.

I've just soldered my Xi 8088 board (after about a month waiting for spare parts) and it doesn't work 🙁

When I boot my system nothing happens (no beeps, no video signal and so on), POS error system shows 00 code. After several attempts (when I changed everything I can, especially old IC bought from eBay), incidentally I clicked of board's reset switch and POS error became 01. I found BIOS source code and found in it, that it can happen only in one place just after CPU warm boot:

errno.inc:
25 e_boot equ 00h ; Boot the OS
26 e_start equ 01h ; BIOS POST started
27 e_cpu_ok equ 02h ; CPU test passed

bios.asm:
1004 warm_start:
1005 cli ; disable interrupts
1006 cld ; clear direction flag
1007 mov al,e_start
1008 out post_reg,al ; POST start code
1009
1010 ;-------------------------------------------------------------------------
1011 ; test CPU's FLAG register
1012
1013 xor ax,ax ; AX = 0
1014 jb cpu_fail

To approve my guess and changed e_start code to 0x79, recompiled BIOS and reran it. After cold and then warm boot I got "79" on POS error screen!
After that instruction, it turns out that BIOS trying test CPU and after then it will send new POST code e_cpu_fail or will make new checks. But it doesn't happen! It seems that just after first "out" command CPU hangs.

I have no idea what I need to check/replace further.

Reply 448 of 614, by Sir Isaac

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widgetii wrote:
Hello, guys. […]
Show full quote

Hello, guys.

I've just soldered my Xi 8088 board (after about a month waiting for spare parts) and it doesn't work 🙁

When I boot my system nothing happens (no beeps, no video signal and so on), POS error system shows 00 code. After several attempts (when I changed everything I can, especially old IC bought from eBay), incidentally I clicked of board's reset switch and POS error became 01. I found BIOS source code and found in it, that it can happen only in one place just after CPU warm boot:

errno.inc:
25 e_boot equ 00h ; Boot the OS
26 e_start equ 01h ; BIOS POST started
27 e_cpu_ok equ 02h ; CPU test passed

bios.asm:
1004 warm_start:
1005 cli ; disable interrupts
1006 cld ; clear direction flag
1007 mov al,e_start
1008 out post_reg,al ; POST start code
1009
1010 ;-------------------------------------------------------------------------
1011 ; test CPU's FLAG register
1012
1013 xor ax,ax ; AX = 0
1014 jb cpu_fail

To approve my guess and changed e_start code to 0x79, recompiled BIOS and reran it. After cold and then warm boot I got "79" on POS error screen!
After that instruction, it turns out that BIOS trying test CPU and after then it will send new POST code e_cpu_fail or will make new checks. But it doesn't happen! It seems that just after first "out" command CPU hangs.

I have no idea what I need to check/replace further.

What CPU are you trying to run?

Reply 449 of 614, by widgetii

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NEC V20, tried to change to another one also

Reply 450 of 614, by Sir Isaac

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widgetii wrote:

NEC V20, tried to change to another one also

That's the CPU I'm using as well. I've also tested a D8088-2 without any errors.

I'd start by double checking any dip switch settings.
Check out your video card to make sure it supports 8 bit mode.
Then maybe have a look around your backplain and CPU board, make sure they're clean with no unwanted solder bridges or flux residue.
After that maybe test all your voltages to make sure they're ok.

If you have an oscilloscope check out the clock line, make sure the signal is half descent looking and it's the right frequency.
Hope that helps get you started 😀

Reply 451 of 614, by widgetii

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Hello,

I started from voltage measurement on CPU (got 5.040 V), after that checked U1 (82c84 clock generator) 8 pin (CLK88) with oscilloscope and got 4.77320MHz

U1P8.jpg?dl=1

and on 12 pin (OSC) I got 14.3196Mhz.

U8P12.jpg?dl=1

Also I figured out that U4 (8288 chip) after few minutes became very hot comparing to other IC. Is it similar to other machines?

Reply 452 of 614, by widgetii

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After several hours with my measurements and datasheets reading incidentally something went right and BIOS began to pass POST test - https://youtu.be/KpllKuoyjTE

But something still wrong - my monitor shows nothing, just a short message "NO SUPPORT" after video BIOS test. I soldered Super VGA card from Sergey ( http://www.malinov.com/Home/sergeys-projects/isa-supervga ), but not sure that made all right. I tried to set a jumper in it also, but nothing changed. Also I have only one VGA compatible monitor (but actually it works) and cannot check board with others.

Reply 453 of 614, by keenerb

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After initial power-on I have to reset the board with the switch on the back before my VGA card works. Powering off and on doesn't do it, it has to be the reset button.

Reply 454 of 614, by Sir Isaac

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widgetii wrote:

After several hours with my measurements and datasheets reading incidentally something went right and BIOS began to pass POST test - https://youtu.be/KpllKuoyjTE

But something still wrong - my monitor shows nothing, just a short message "NO SUPPORT" after video BIOS test. I soldered Super VGA card from Sergey ( http://www.malinov.com/Home/sergeys-projects/isa-supervga ), but not sure that made all right. I tried to set a jumper in it also, but nothing changed. Also I have only one VGA compatible monitor (but actually it works) and cannot check board with others.

Your clock signals look good. It definitely seems to be posting the cpu card right. You can tell just by the sound and post display.
I went with the 82C88 (same chip less power). Can't be sure but I know original series chips use way more power and can get very warm. I installed an 8087 co-processor and you could fry eggs on it. It didn't sit well with me having it that hot so I stuck a few small heat sinks on it.

I just barley completed the vga card, and it works great. I'm using the D4.01E.bin bios from Sergey's site.
What type memory did you get for the card? I'd inspected the vga chipset again under some magnification just to make sure.
Do you have another ISA video card you could test it with?

I'm using the same PSU. It's great small, quiet and lots of power for this build.

Reply 455 of 614, by Sir Isaac

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keenerb wrote:

After initial power-on I have to reset the board with the switch on the back before my VGA card works. Powering off and on doesn't do it, it has to be the reset button.

That's odd I don't have to do that.
I'd check the ic's your using in the power section on the back-plain. It's recommended for U5 and U7 to use 74HCT. Also check the IC's in the clock and reset section on the cpu board. I think this is where the power on reset circuit is.

Reply 456 of 614, by widgetii

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For DRAM I use 4 pcs Motorola MCM514256 and they are new. I soldered two VGA cards and none of them works 🙁(

There are two kinds of problems can be: poorly soldered main IC Trident (but I checked it several times, cannot guess how to actually check) and my new monitor with VGA input, which won't work with current signal (checked with other VGA output devices, such netbook, it works).

Reply 457 of 614, by widgetii

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I've just checked VGA cable connected to Super VGA card with multimeter and found that 13 pin has 31,48kHz and 14 pin has 70Hz that seems to be standard text mode - http://tinyvga.com/vga-timing/640x400@70Hz

Very strange that my monitor won't work with this mode. By the way, anybody knows something about HSYNC_SEL jumper?

Reply 458 of 614, by Sir Isaac

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widgetii wrote:

For DRAM I use 4 pcs Motorola MCM514256 and they are new. I soldered two VGA cards and none of them works 🙁(

There are two kinds of problems can be: poorly soldered main IC Trident (but I checked it several times, cannot guess how to actually check) and my new monitor with VGA input, which won't work with current signal (checked with other VGA output devices, such netbook, it works).

The memory should be good as long as it's 70ns or less. I went with 4x MT4C4256-70 (512KB total)
It definitely could be a bad solder job, sometimes bridges are hard to spot. I assume you cleaned the board really well, made sure there's no extra flux.

widgetii wrote:

I've just checked VGA cable connected to Super VGA card with multimeter and found that 13 pin has 31,48kHz and 14 pin has 70Hz that seems to be standard text mode - http://tinyvga.com/vga-timing/640x400@70Hz

Very strange that my monitor won't work with this mode. By the way, anybody knows something about HSYNC_SEL jumper?

According to the silkscreen on the card 🤣 😊
Horizontal frequency
open >= 48.7Khz
closed <= 48.7khz

Last edited by Sir Isaac on 2017-10-20, 00:56. Edited 1 time in total.

Reply 459 of 614, by smbaker

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Also be sure to check the seating of all cards in the backplane. I'm not entirely sure why, but sometimes I'll have POST errors until I fidget with the Xi 8088 card a few times and then it'll work fine for several days or even weeks. I used some eBay card connectors on my backplane -- maybe they weren't the best quality.

For checking solder bridges, I'm a fan of using a stereo microscope. AmScope has some pretty affordable ones. That big SMD chip on the VGA card in particular took me multiple passes of retouching it, picking at the pins to make sure they were soldered down good, cleaning up bridges, etc.