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zippysticks
November 29th, 2017, 10:21 AM
Folks,

Bought a Superbrain that powers up to disk prompt but did not come with any software.

Boot disk has arrived from the US (retro System Rescue) today but I seem to have a problem.

Computer recognises disk appears to read and start CP/M but the display is corrupt on boot (see screen shots)

Any ideas ?

I'm not sure if its the boot disk software or perhaps a problem with video memory on the Superbrain as I seem able to enter commands and get responses from the computer even though I cant read the output from the screen.
For example the DIR<CR> command produces some output as does a switch to the B drive with B:<CR> followed by another DIR<CR> command on the 2nd drive.

Anyone able to create me another Boot disk so I can try it ? Or does it seem likely to be a machine problem ?

Thanks in advance.

42186
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zippysticks
November 29th, 2017, 11:52 AM
The more I think about this the more I believe that the machine is ok and that the boot disk I have been supplied is somehow not in the correct format.

This is a QD (Quad Density drive machine) and I have been given a relatively modern DS/DD disk with the Superbrain software on it.

Silly question perhaps but is this disk compatible with the machine ?
I have no idea how Retro System Rescue produced the disk - whether it was done on a Superbrain or from some PC based toolset from a file image and compatible (or incompatible drive)

It clearly does boot the machine albeit with a corrupt display as I can issue CP/M commands, change drives etc but display remains corrupt.

Thoughts anyone ?


Folks,

Bought a Superbrain that powers up to disk prompt but did not come with any software.

Boot disk has arrived from the US (Retro System Rescue) today but I seem to have a problem.

Computer recognises disk appears to read and start CP/M but the display is corrupt on boot (see screen shots)

Any ideas ?

I'm not sure if its the boot disk software or perhaps a problem with video memory on the Superbrain as I seem able to enter commands and get responses from the computer even though I cant read the output from the screen.
For example the DIR<CR> command produces some output as does a switch to the B drive with B:<CR> followed by another DIR<CR> command on the 2nd drive.

Anyone able to create me another Boot disk so I can try it ? Or does it seem likely to be a machine problem ?

Thanks in advance.

krebizfan
November 29th, 2017, 12:04 PM
DS/DD disks should work with QD density drives. The disk media is supposed to be the same; the QD drive just uses half width tracks. It is possible the disk is bad but it would have to have failed in an unlikely fashion to have the display issue shown. More likely would be failure of video RAM or video controller (intermittent since sometimes you can see display).

I don't know if the Superbrain will do it but with other CP/M machines, one could switch to using a serial port terminal instead of the screen display. If it works over the serial port, then the problem will have been narrowed down to the display subsystem.

zippysticks
November 29th, 2017, 12:11 PM
Thanks, I could try the serial port but not sure whether the ROM monitor will talk to the port until CPM is loaded. I'll find out.

Reason I thought it might be the floppy is because I just happened to try some other CP/M disks that came with my Northstar - some hard and some soft secotored. All appeared to produce output with corrupt graphics/characters on the screen after booting. Having said that none of the Northstar CPM disks resulted in the ability to issue commands successfully. Not sure how binary compatible those disks contents are with the Superbrain of course.

Chuck(G)
November 29th, 2017, 12:12 PM
You haven't indicated your location in your profile, so one can only assume that you're located on Tristan da Cunha.

If you have a suitable 'tweener, I believe that the Maslin archive has several SB images, for both 48 and 96 tpi drives.

zippysticks
November 29th, 2017, 12:32 PM
Updated my profile location - I'm in the UK.
I can find the images - thanks - but don't have a machine/drive to produce the disks with.

krebizfan
November 29th, 2017, 12:38 PM
Thanks, I could try the serial port but not sure whether the ROM monitor will talk to the port until CPM is loaded. I'll find out.

Reason I thought it might be the floppy is because I just happened to try some other CP/M disks that came with my Northstar - some hard and some soft secotored. All appeared to produce output with corrupt graphics/characters on the screen after booting. Having said that none of the Northstar CPM disks resulted in the ability to issue commands successfully. Not sure how binary compatible those disks contents are with the Superbrain of course.

Given the Northstar issues, it may be that the Superbrain disk you have is also configured incorrectly for the display setup on your specific Superbrain. Opening it up, photographing the cards, dumping any ROMs, and hoping that all provides some type of clue as to what needs to be done might be a viable next step.

zippysticks
November 29th, 2017, 12:44 PM
Given the Northstar issues, it may be that the Superbrain disk you have is also configured incorrectly for the display setup on your specific Superbrain. Opening it up, photographing the cards, dumping any ROMs, and hoping that all provides some type of clue as to what needs to be done might be a viable next step.


Sorry, let me clarify - I don't have any Northstar issues - that machine works with all its disks. Its the use of Northstar disks in the Superbrain that don't work.
I'll post more details on the mainboard config (there is only one board) and ROM dumps - if I can get an adaptor to read them.
I have read quite a bit regarding ROM corruption but not sure that is the case here as the machine appears broadly functional - corrupt screen on boot from disk aside.

zippysticks
November 29th, 2017, 12:50 PM
Hmm - just got this back from Retro System Rescue:

"Hi – it is a Double Density Disk for use on the Standard Superbrain – if you have a QD Superbrain it will not work. They are made on a PC using original disk images and then checked on the pc to verify that they contain the correct data."

I guess that answers my question......

Can anyone produce a boot disk for me please ? - at my expense of course.

Thanks in advance

JonB
November 30th, 2017, 04:09 AM
Hey zippysticks

You're in the South East of the UK? Where? I'm on the Coast near Brighton. I have Superbrains (yes, plural!) and boot disks. Happy to share.

One thing to look out for is custom ROMs (right above the 7 key on the keypad). A common hack was to get access to all 40 tracks on the floppy drive (default is 35) and this can prevent stuff from working (although not the boot, to be fair). At least one of the Maslin images is a 40 tracker.

[edit: I see you have an Intertec ROM, good!]

The other thing to look out for is 60hz CP/Ms (I think all the Maslin images are 60hz). These will set the video chip to 60Hz rather than 50Hz and this results in a dreadfully corrupted display.

You can PM me if you want to know more.

Cheers
jonB

zippysticks
November 30th, 2017, 05:31 AM
Hey zippysticks

You're in the South East of the UK? Where? I'm on the Coast near Brighton. I have Superbrains (yes, plural!) and boot disks. Happy to share.

One thing to look out for is custom ROMs (right above the 7 key on the keypad). A common hack was to get access to all 40 tracks on the floppy drive (default is 35) and this can prevent stuff from working (although not the boot, to be fair). At least one of the Maslin images is a 40 tracker.

[edit: I see you have an Intertec ROM, good!]

The other thing to look out for is 60hz CP/Ms (I think all the Maslin images are 60hz). These will set the video chip to 60Hz rather than 50Hz and this results in a dreadfully corrupted display.

You can PM me if you want to know more.

Cheers
jonB

Hi Jon,

I'm in Horsham so not too far. Thanks for the offer. Pretty sure I just need a boot disk and perhaps a Kermit or other PC link up program to get this Superbrain working - will PM.

By the way have just acquired a broken Acorn Electron for its keyboard to try and replace the two I have missing. Have just offered up so far and I'm not sure yet but they look ever so slightly smaller than the Superbrain keys but should still fit on the plunger that has snapped in both cases.

JonB
November 30th, 2017, 07:45 AM
I don't think they are the same. Try taking a switch from the SB and Electron, see if it's got an SMC logo on it.

zippysticks
November 30th, 2017, 10:14 AM
You are right of course - keycap has different profile and switch configuration is different. Back to plan A to salvage mechanism from on of my (broken) BBC masters.

JonB
November 30th, 2017, 10:27 PM
Ah.. you didn't say you had a broken Master. And here's me telling you to get switches from Retro Clinic. LOL.