• Please review our updated Terms and Rules here

XT board questions (FT SUPER-640 )

Chuck(G) said:
As an interesting unrelated tidbit, I run a 5MHz V20 at 8MHz with no problem (i.e. it doesn't fail and there's no overheating).
Click to expand...

Another interesting tidbit, I run an 8MHz V20 at 5MHz!
Regarding the real problem, I don't think it could beep the speaker or make the kb flash if it had a dead CPU.
 
i've got that same board, that works, i don't think it's got a CPU on it right now though. Your missing all your rom chips though, and i'm sure that white goo isn't helping things at all. What's that rom in socket 7 there? I have 5 roms in mine -4 basic roms and a generic XT bios. board works great with the 8088-2 from my Zenith Z-158 *only 8088-2* i have.
 
k2x4b524[ said:
i've got that same board, that works, i don't think it's got a CPU on it right now though. Your missing all your rom chips though, and i'm sure that white goo isn't helping things at all. What's that rom in socket 7 there? I have 5 roms in mine -4 basic roms and a generic XT bios. board works great with the 8088-2 from my Zenith Z-158 *only 8088-2* i have.
Click to expand...

That rom in socket 7 is theoretical a BIOS (I never managed to make her boot), I tried another BIOS from another identical board (the twin board also don't boot), I'm in a kind of dead end here. Someone told me that is possible to reflash your faulty ROM with another good and identical board, in a 486. ie: you boot up the good system, open the flash utility, do the arrangements, remove your current BIOS (without turning the system off) t, put the faulty in place, and reflash it. With this kind of procedure, I will be able to determine if my problem is on BIOS ROM?
A have several good 486 boards, that uses the same ROM size (physically).
 
The ROM in the 7th socket is mapped into F200:0 if my arithmetic is right. As this isn't scanned for by the BIOS boot routines, it's pretty much useless, except as for spare storage--or custom code if you're writing your own BIOS.

Some Far East PC XT clones have 8 sockets for the entire F000:0-FE00:1FFF memory range. Some have pads for an eighth socket, but no socket. Chip select is provided by an LS138 usually, so the only thing that matters is PCB real estate.
 
I'm still concerned about the exactly location of CPU, some similar boards is Stason shows the cpu in the upper socket, another boards show the CPU in the lower socket, I'm confused about this. I was looking datasheet for the 8088 and 8087, and I don't think I will cause any damage to the 8088 if I put it on the 8087 socket, same grounds and vcc pins, I'm correct? Also Chuck said that the BIOS is in a socket that won't be scanned for BIOS boot routines, should I put it on another (what?) socket?
 
I've got a board that's very close to yours. In the TH99 web page that you cited, the BIOS is in the proper socket, but the CPU is in the wrong socket. My CPU is in the socket closer to the expansion connector and the NPU is in the socket closest to the power supply connector.

Look at the figures of the various 8088 ERSO motherboards at TH99--note where the CPU socket is in relation to the NPU when both are close to the power supply connector. I suspect that in your case, the diagram is in error.

All of these Taiwanese boards are derived from a common ERSO reference design. There would be no reason to swap the locations of the two chips.
 
Did you ever get the board working ? I have two similar boards .....
1) similar to yours but has the 8 ROM sockets as mentioned earlier ...works okay has IBM Basic ROMS installed
2) also similar but only has 6 ROM sockets ....doesn't work...this one had a clock card with a battery which dripped some
liquid onto the board and damaged a few lands......havent tried to repair it yet

I recently installed the working board in an XT Clone case

Here's a couple pictures of the working board :
 

Attachments

  • DSCF0090.jpg
    DSCF0090.jpg
    101.4 KB · Views: 4
  • DSCF0091x.jpg
    DSCF0091x.jpg
    103.6 KB · Views: 4
Last edited:
Hmm, one difference, mine doesn't say TURBO on the board anywhere.
And there is no jumper on the board for turbo or turbo switch.
Booting up and hitting Ctrl-Alt-<keypad "-"> doesn't appear to do anything.
So, I'm wondering if this is even a turbo board...... it does have a NEC V20 10Mhz.
 
these boards are very similar to mine! I will get a known working cpu and bios rom to try with her, should work...I love those basics rom, wish I someday I could get this.
 
I can't figure out how to switch my board into Turbo mode....there are no jumpers on the board
itself that appear to be for setting this....and CTRL-ALT-<minus> doesnt appear to work. I ran
the Landmark speed test and it says its running at 4.77 Mhz.

I suspect that it may be software switchbable only, and possibly the BIOS on my board doesn't
support turbo. Seeing as how all (4) IBM Basic ROMS are present I wonder if the previous owner
also burned/installed the genuine IBM XT BIOS. I'll try dumping the BIOS and see what I can discover.
 
Looking around in the ROM BIOS on my XT Clone board...... I see that it is a (copied) IBM XT BIOS ROM
.....in addition to the IBM BASIC ROMS.

The BIOS date which I found using DEBUG
debug
- d FFFF:5 L 8 30 38 2F-31 36 2F 38 32 08/16/82

I also did a search for the part number 5000026 which was found in the BIOS at F000:E000

XT BIOS date 08/16/82 coincides with the following information I found on modem7's site:

From modem7 website "Some information sources indicate that there was an additional revision of the BIOS, one dated 08/16/82. For that BIOS, we expect chip U18 to have the IBM part number of 5000026 on it. I have yet to see a "5000026" stamped U18 chip. It is possible that the BIOS was never released."
 
Last edited:
mikey99 said:
Did you ever get the board working ? I have two similar boards .....
1) similar to yours but has the 8 ROM sockets as mentioned earlier ...works okay has IBM Basic ROMS installed
2) also similar but only has 6 ROM sockets ....doesn't work...this one had a clock card with a battery which dripped some
liquid onto the board and damaged a few lands......havent tried to repair it yet

I recently installed the working board in an XT Clone case

Here's a couple pictures of the working board :
Click to expand...


I finally got the known working BIOS EPROM and a 8088, but still don't boot! Will try known good ram chips now.
 
I forgot to say that I have two almost identical boards here, and the another did worked very well, it has a phoenix bios. But it aren't changing the prompt with "Crtl + Alt + (keypad) -" Any clues? And by the way, real thanks to everyone, especially to you Chuck. Without you guys, I would not never seen this board working! Thanks!
 
when it boots I can read:
Phoenix ROM BIOS 2.27

this is that white goo (as k2x4b524[ called it) from the picture.
 
Well, just about any 'Turbo" 8088 ERSO BIOS should work with both boards and get you your keyboard-controlled speed changer going. There should be an image wandering around on the web--if not, let me know and I'll post one.
 
I tried to use a BIOS from a DTK 8088 clone board (Chromedome45 made the copies to me), but the board beeped like a crazy phone. Maybe it's possible to change the speed using a custom built program?
 
I have two very simlar clone boards. One I use as a test bed. The BIOS in both boards has a checksum other than 00. They both boot.
Interesting text message in each BIOS is "Beware this BIOS By Edward S. ONealhas traps if modified" might account for the odd checksum(s).
The MCT BIOS is from a turbo board that looks like Lucasdatona's picture except no second power supply connector , the JD BIOS is from a board that looks exactly like the picture Lucasdaytona posted.
Perhaps one of these will boot your board.

edit: The BIOS image I labeled MCT has a sticky label on the 2764 that says "MCT BIOS (c) 1985 E.S. Oneal":, there is a text message in the image licensing it to JD Microdevices.

The BIOS I labeled JD has a sticky label on the 2764 that says "1153 JD BIOS 01/27/86", there is a text message in the image licensing it to Progressive Electronics.

I suspect both of these are from JD Microdevices.
 
Last edited:
You must log in or register to reply here.
Back
Top