My BBC B won't boot with a SMART SPI or DFS 0.9

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CommanderCoder
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My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Fri Nov 22, 2019 7:11 pm

This thread starts in my introduction but it is really a hardware problem (viewtopic.php?f=13&t=18212)

Because my BBC won't boot up into DFS I've bought a SMART SPI from RetroClinic. I removed the DFS chip and installed the SPI chip and put the SD Card board into the User Port. With this configuration, when I turn the BBC B on, it simply shows "BBC Microcomputer 32k" and nothing else. I moved the EPROM around and into the rightmost slot but it didn't help.

I plugged the same setup for SMART SPI into my BBC Master and it all works. I can run games from the SD Card on my Master.

So, the question is: is there anything that could be a common problem between the BBC B DFS problem (I thought it was the FDC chip) and the SMART SPI problem in this BBC?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by KenLowe » Fri Nov 22, 2019 7:15 pm

Check to see if you have jumpers installed in S20, S21 & S22. If your beeb previously had a rom expansion board, these jumpers may have been removed.

S20: should be NORTH
S21: 2 jumpers should be EAST/WEST
S22: Should be NORTH

Out of interest, does it boot to the BASIC > prompt?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by Wheel_nut » Fri Nov 22, 2019 9:34 pm

Does your Beeb have the Econet Hardware installed? If so, unless the Econet is connected and active, I believe that there is a Jumper which has to be set.

I am not sure of the detail as I don't have Econet on any of my Beebs.
Last edited by Wheel_nut on Fri Nov 22, 2019 10:49 pm, edited 1 time in total.
#1 BBC Model B Issue 7 + 1770 DFS + Dual TEAC Floppy
#2 BBC Model B Issue 7 + 8271 DFS + Dual Floppy + Speech
#3 BBC Model B Issue 7 + 8271 DFS + Cumana Single Floppy

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by Boydie » Fri Nov 22, 2019 10:13 pm

That would be S2. Also make sure S9 is made, otherwise it’ll still be looking for a disc interface that may or may not be there (but may have been in the past).

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Sat Nov 23, 2019 11:04 am

The computer boots up to BASIC if I hold down the T key with BREAK when the DFS is installed. With the SMART SPI it wouldn't boot to anything.

I checked the jumpers and they are all as you say below.

It looks like an ECONET interface has been installed.
KenLowe wrote:
Fri Nov 22, 2019 7:15 pm
Check to see if you have jumpers installed in S20, S21 & S22. If your beeb previously had a rom expansion board, these jumpers may have been removed.

S20: should be NORTH
S21: 2 jumpers should be EAST/WEST
S22: Should be NORTH

Out of interest, does it boot to the BASIC > prompt?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 1:49 pm

Does your Beeb have either DIP switches or wire links fitted to the keyboard PCB near the Delete and Copy keys (see photo)?
40DFB7D1-C47C-4D5D-A53C-7392E7A2C22E.jpeg
Position where a DIP switch or wire links can be fitted
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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 2:04 pm

More information here :wink:

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Sat Nov 23, 2019 3:06 pm

I'm afraid not. It is just a gap like in your picture. Here is a picture of the motherboard though. Maybe there is a link out of position somewhere. If you want a close up of any bit, I can oblige.
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IMG_6645.JPG

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 3:34 pm

Do all the keys on the keyboard work correctly?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Sat Nov 23, 2019 3:44 pm

Yes. The keyboard works okay. Actually a few of the keys were troublesome for a few hours when I unpacked machine after 20 years of no use but with a bit of persistence and some resoldering they all work now.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 3:53 pm

Okay, if all the keys work (including both shift keys and the CTRL key ( test by pressing CTRL and G, the machine should beep), then it’s unlikely to be a keyboard decoding fault.

To sum up so far, you get the same problem with the DFS 0.9 EPROM fitted and with the SMART SPI EPROM fitted. With neither fitted, the machine works correctly.

With the DFS 0.9 EPROM fitted, you can get to the BASIC command line by pressing BREAK while holding ‘T’.

Try swapping the two 6522 VIA chips around. IC3 is the ‘system’ VIA, IC69 is the ‘user’ VIA.

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Last edited by 1024MAK on Sat Nov 23, 2019 4:02 pm, edited 1 time in total.
Reason: Correct typo!

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 4:32 pm

If swapping the VIAs does not work, try this program to see what configuration the machine thinks it’s set to:

First, the [ key, do you get a left arrow or a square bracket? If you get an arrow, the current screen mode is MODE 7. Switch to MODE 6 (type ‘MODE 6’).

Then type in this program:

Code: Select all

10 A%=255
20 X%=0
30 Y%=255
40 P. ~(USR &FFF4 AND &FF00)DIV256
Run it and report back what it prints out.

Mark
Last edited by 1024MAK on Wed Nov 27, 2019 11:05 pm, edited 1 time in total.
Reason: Edited to change the last number in the BASIC program line 40 from 255 to 256.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Sat Nov 23, 2019 6:24 pm

Switching the VIAs didn't make any difference.

Running that code gave the result : 100

I think you might have meant 'DIV 256'

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 8:16 pm

100 is the same as one of my BBC B machines, so that’s okay.

The program is taken from BeebMaster’s site, so I deny any knowledge of any errors :lol:

Note: since originally posting the program, I have changed the 255 value to 256. The result of 100 was with the old value of 255...

So we can rule out the keyboard and the VIA.

So the question is, why is the OS hanging, presumably waiting for a non existent disk drive operation.

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Last edited by 1024MAK on Wed Nov 27, 2019 11:06 pm, edited 1 time in total.
Reason: Edited

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Sat Nov 23, 2019 8:19 pm

What test gear do you have?

Multimeter?
Logic Probe?
Logic analyser?
Oscilloscope?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by duikkie » Sun Nov 24, 2019 8:46 am

Make the beeb like a tape machine see wat happens then

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Sun Nov 24, 2019 2:19 pm

I have a very old oscilloscope which isn't very accurate or easy to read but it'll show me roughly if a line has something like a proper signal on it.

If I remove the DFS ROM the machine boots into TAPE and that works.

I tried remove as many chips as possible that are socketed (ECONET, FDC, ROMS) and it seems to work with a minimum set.

It is more than the DFS ROM because the SPI doesn't work.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by duikkie » Sun Nov 24, 2019 5:41 pm

Oke what happens if you move the basic rom to an other socket ? And Do other rom like exmon work? Dfs work with other chips then smart spi rom maybe your rom select lines are not working?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by hoglet » Sun Nov 24, 2019 8:06 pm

Here's a suggestion from Steve Picton:
Try removing the eight links from S11, about an inch to the left of the D7002 A/D converter
If you search the forum for S11 and Econet, it seems others have hit this problem in the past, and this has resolved it.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Mon Nov 25, 2019 8:06 pm

I removed the end link from the S11 so that the ECONET thinks the number is 3 rather than 1 and the SMART SPI works. ( I put the link on the composite video so I get colour out of the CBVS now).

I moved the ROMS around so that the machine boots up to Smart SPI. This is good.

If I hold down D and press BREAK, then I'm still getting the DFS problem. At least I can dump the DFS rom to the SD Card now and compare the image with a good image to check the ROM isn't broken.

I suspect I have a dodgy 8271 so I'll order one of those (if beebmaster has any still available). Is there an easy way to check if the FDC is broken?

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by 1024MAK » Wed Nov 27, 2019 10:29 am

Realistically, the only easy way to tell if the 8271 FDC chip is working okay is to connect a good working floppy drive to your machine and then try to read from and write to a floppy disk.

The 8271 FDC chip won’t do anything unless the filing system that controls it (the DFS ROM in your case) gives it a command.

Normally when both a FDC chip and a suitable filing system ROM are fitted, the OS will pass control to the filing system so that it can set itself up. The filing system checks to see if a FDC chip is present. If yes it sets up an area of memory ready. Then later in the start-up sequence, the OS will check to see if it should auto-boot a file from disk (e.g. the user has pressed SHIFT-BREAK or the appropriate keyboard configuration link has been fitted). If yes, it will then try to load from disk.

If there is no suitable filing system, the OS will ignore the 8271 FDC chip (apart from interrupts). If there is a disk filing system but no FDC chip, then the disk filing system will not initialise and the OS won’t try to auto-boot from it.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by BeebMaster » Wed Nov 27, 2019 11:42 am

1024MAK wrote:
Sat Nov 23, 2019 4:32 pm
If swapping the VIAs does not work, try this program to see what configuration the machine thinks it’s set to:

First, the [ key, do you get a left arrow or a square bracket? If you get an arrow, the current screen mode is MODE 7. Switch to MODE 6 (type ‘MODE 6’).

Then type in this program:

Code: Select all

10 A%=255
20 X%=0
30 Y%=255
40 P. ~(USR &FFF4 AND &FF00)DIV255
Run it and report back what it prints out.

Mark
Where is that and what's it for? Something to do with testing the keyboard links?
Image


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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Wed Nov 27, 2019 12:55 pm

To shift the upper byte down to the lower byte you should divide by a power of 2, i.e. 256 (&100).

I might be mistaken, but that bit of code looks wrong.

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by duikkie » Wed Nov 27, 2019 4:51 pm

what is easy :)

you can program the 8271 chip in MC , but MC programming is easy low level , and low is easy :evil: :mrgreen:

1024MAK wrote:
Wed Nov 27, 2019 10:29 am
Realistically, the only easy way to tell if the 8271 FDC chip is working okay is to connect a good working floppy drive to your machine and then try to read from and write to a floppy disk.

The 8271 FDC chip won’t do anything unless the filing system that controls it (the DFS ROM in your case) gives it a command.

Normally when both a FDC chip and a suitable filing system ROM are fitted, the OS will pass control to the filing system so that it can set itself up. The filing system checks to see if a FDC chip is present. If yes it sets up an area of memory ready. Then later in the start-up sequence, the OS will check to see if it should auto-boot a file from disk (e.g. the user has pressed SHIFT-BREAK or the appropriate keyboard configuration link has been fitted). If yes, it will then try to load from disk.

If there is no suitable filing system, the OS will ignore the 8271 FDC chip (apart from interrupts). If there is a disk filing system but no FDC chip, then the disk filing system will not initialise and the OS won’t try to auto-boot from it.

Mark

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by BeebMaster » Wed Nov 27, 2019 10:03 pm

CommanderCoder wrote:
Wed Nov 27, 2019 12:55 pm
To shift the upper byte down to the lower byte you should divide by a power of 2, i.e. 256 (&100).

I might be mistaken, but that bit of code looks wrong.
Yes, it should be DIV&100 to mask off the X register, I'll have to fix that at some point. Eventually.
Image

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Re: My BBC B won't boot with a SMART SPI or DFS 0.9

Post by CommanderCoder » Mon Dec 02, 2019 11:29 pm

Cheers everyone. I got a sideways RAM chip working and installed DFS0.9 onto that from my SmartSPI and it still hangs on boot. Maybe the FDC is broken, maybe it is something else. I'll keep hunting around that area of the board for bad joints and let you know if/when I manage to fix it.

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