Oh my gosh! I could not believe my eyes when you turned the BBC Master over. “K&K Computers”, I worked in the shop at weekends when I was in my teens and evolved to full time as I got older. This is the first time I have seen a computer sold by K&K on CZcams. Ah the good old 8bit days.
One thing I did learn about EPROMS about 10 years ago was that erasing them with environmental light is harder than people think. We had a Farley Wizard plasma cutter at work that was forever going wrong and the cabinet door was constantly open near to a bunch of welding bays, EPROM exposed and it’s code never slipped away. In the end we scrapped it for being too old and worn to cut decently.
I have a book "Experiments with EPROMS". It has a load of EPROM based circuits you can create. After several decades I'm now finally thinking of having a play with some.
I've got a BBC Model B+ which can use 32kByte EPROMs, such as the 27256. You can program them with two sideways ROM images so, for example, I have View and ViewSheet stored on one chip, occupying one physical ROM socket but providing two 16kByte sideways ROMs. The 28C256 is an EEPROM, which can be reprogrammed without the need to be erased with UV light and is still being manufactured, which make it more convenient. It's also almost pin compatible with the 27256, but not quite. There are two pins that are different, so I made a small PCB with header pins that fit into a sideways ROM socket on one side and a surface mount SOIC version of the 28C256, a pull-up resistor and a pair of jumpers on the other side. If you set the jumpers to the Program position the chip is connected directly to the pins and you simply plug it into the programmer. When you've programmed and verified it you can put the jumpers in the other position and it looks to the Beeb like a 27256.
Ah that's really interesting. I have one of those old chips I extracted from something. I've got a data sheet for it somewhere. I seem to remember it needed 20v or something to program it. I hadn't realised that the way the UV thing works is to change all the bits to 1's. I'd kinda assumed you had to apply the high voltage AND the UV to it while programming but that programming could set 0's or 1's. Totally failed to appreciate that the programming can only flip a 1 to a zero. Fascinating stuff!
The non-A ones need 20V but the A versions only 12.5V. I think 12.5V became more the norm later as, if I select the 27128 (16KB) one, it defaults to 20V, but if I pick the larger 27256 (32KB), it defaults to 12.5V. You can change both with the secret Ctrl+V combination. I've broken one or two EPROMs by forgetting to set the voltage! The usually fail immediately and, even after erasing them, you can never program them again.
I used BBC-b / Masters at collage. Even kept the 5.25 floppies hoping I could recover whats on them but these don't seem to work on an old BBC b micro I have laying around now "missing update roms for the filesystem being ADFS?" The disks have been kept in very good condition in there original Dixons brand box. *cat shows the disks contents without any issues but loading anything else brings up error 18 and a random hex value so there could be an issue with the 40 Track 'Tec 501' drive if not the disks themselves. I never know about eproms for those computers, very interesting... just good old tape, disk or econet.
Yep - the BBC Micro had an SAA5050 chip for the MODE 7 teletext display. The BBC insisted on that in the spec to support their teletext service, as well as being used for the things like the Prestel viewdata service. It gives really nice clear text, even today.
What modern device do you use? I'm looking for something to let me burn eproms or even eeproms if possible for the beeb I'm in the process of restoring. Thanks
@@8bitmark530 mine's a TL866 (pretty common one) and burns a huge list of eproms as well as can we used as a chip tester. Such as a lot of 74LS chips etc
If the EEPROM fails because off too many program/erase cycles (not because you programmed it with the wrong voltage) you can try restoring it (by releasing the electrons from stuck cells) by baking the EEPROM in an oven. At least that was the case with the very first EEPROMS that came to market, like the 2708 which could only be erased a couple of times, but I think the same mechanism will also work with later EEPROMS, you can try it. Bake them at 200 degrees for say 30 minutes. and see if there are still bits stuck at zero.
Excellent stuff. Question: when I now switch my Master on all I get is a continuous beep at startup and I can't type on the keyboard. Any ideas? Regards Kevin
Thank you for the video. Is the "beeb" mac terminal tool still available somewhere? I searched for "beeb mac os x ssd disc tool" and variations but couldn't find it. I've been trying to get ROM images onto my Electron via GoSDC to load into sideways RAM, but never managed it.
Yup - you can download it here: github.com/sweharris/MMB_Utils There's also this graphical tool, if you'd prefer one of those: stardot.org.uk/forums/viewtopic.php?t=19802
Oh my gosh! I could not believe my eyes when you turned the BBC Master over. “K&K Computers”, I worked in the shop at weekends when I was in my teens and evolved to full time as I got older. This is the first time I have seen a computer sold by K&K on CZcams. Ah the good old 8bit days.
One thing I did learn about EPROMS about 10 years ago was that erasing them with environmental light is harder than people think. We had a Farley Wizard plasma cutter at work that was forever going wrong and the cabinet door was constantly open near to a bunch of welding bays, EPROM exposed and it’s code never slipped away. In the end we scrapped it for being too old and worn to cut decently.
I have a book "Experiments with EPROMS". It has a load of EPROM based circuits you can create. After several decades I'm now finally thinking of having a play with some.
I think 30 mins in that eraser is cooking your eproms. 7 minutes is what I have found to be the sweet spot.
I've got a BBC Model B+ which can use 32kByte EPROMs, such as the 27256. You can program them with two sideways ROM images so, for example, I have View and ViewSheet stored on one chip, occupying one physical ROM socket but providing two 16kByte sideways ROMs. The 28C256 is an EEPROM, which can be reprogrammed without the need to be erased with UV light and is still being manufactured, which make it more convenient. It's also almost pin compatible with the 27256, but not quite. There are two pins that are different, so I made a small PCB with header pins that fit into a sideways ROM socket on one side and a surface mount SOIC version of the 28C256, a pull-up resistor and a pair of jumpers on the other side. If you set the jumpers to the Program position the chip is connected directly to the pins and you simply plug it into the programmer. When you've programmed and verified it you can put the jumpers in the other position and it looks to the Beeb like a 27256.
Ah that's really interesting. I have one of those old chips I extracted from something. I've got a data sheet for it somewhere. I seem to remember it needed 20v or something to program it. I hadn't realised that the way the UV thing works is to change all the bits to 1's. I'd kinda assumed you had to apply the high voltage AND the UV to it while programming but that programming could set 0's or 1's. Totally failed to appreciate that the programming can only flip a 1 to a zero. Fascinating stuff!
The non-A ones need 20V but the A versions only 12.5V. I think 12.5V became more the norm later as, if I select the 27128 (16KB) one, it defaults to 20V, but if I pick the larger 27256 (32KB), it defaults to 12.5V. You can change both with the secret Ctrl+V combination.
I've broken one or two EPROMs by forgetting to set the voltage! The usually fail immediately and, even after erasing them, you can never program them again.
Bonjour, je decouvre les bbcmaster et je sens que je vais aimer. Merci
With some clever planning, one can use EPROMS as combination logic devices to save space on circuit boards.
I used BBC-b / Masters at collage. Even kept the 5.25 floppies hoping I could recover whats on them but these don't seem to work on an old BBC b micro I have laying around now "missing update roms for the filesystem being ADFS?" The disks have been kept in very good condition in there original Dixons brand box. *cat shows the disks contents without any issues but loading anything else brings up error 18 and a random hex value so there could be an issue with the 40 Track 'Tec 501' drive if not the disks themselves.
I never know about eproms for those computers, very interesting... just good old tape, disk or econet.
That eprom software looks like teletext 😂 takes me back.
Yep - the BBC Micro had an SAA5050 chip for the MODE 7 teletext display. The BBC insisted on that in the spec to support their teletext service, as well as being used for the things like the Prestel viewdata service.
It gives really nice clear text, even today.
@@lsbyte cool thanks for the info 👍🏻
Really enjoyed that. I burn eproms for my beeb on a modern device but have always wondered how it would work using real old hardware. :)
What modern device do you use? I'm looking for something to let me burn eproms or even eeproms if possible for the beeb I'm in the process of restoring. Thanks
@@8bitmark530 mine's a TL866 (pretty common one) and burns a huge list of eproms as well as can we used as a chip tester. Such as a lot of 74LS chips etc
@@RetroMarkyRM thanks
If the EEPROM fails because off too many program/erase cycles (not because you programmed it with the wrong voltage) you can try restoring it (by releasing the electrons from stuck cells) by baking the EEPROM in an oven. At least that was the case with the very first EEPROMS that came to market, like the 2708 which could only be erased a couple of times, but I think the same mechanism will also work with later EEPROMS, you can try it. Bake them at 200 degrees for say 30 minutes. and see if there are still bits stuck at zero.
How interesting! I have a bunch to try that on, Thanks!!
Excellent stuff.
Question: when I now switch my Master on all I get is a continuous beep at startup and I can't type on the keyboard. Any ideas? Regards Kevin
I think you probably want to head over to the StarDot 8-bit forum - they're the best people to help you: www.stardot.org.uk/forums/viewforum.php?f=3
Thank you for the video. Is the "beeb" mac terminal tool still available somewhere? I searched for "beeb mac os x ssd disc tool" and variations but couldn't find it. I've been trying to get ROM images onto my Electron via GoSDC to load into sideways RAM, but never managed it.
Yup - you can download it here: github.com/sweharris/MMB_Utils
There's also this graphical tool, if you'd prefer one of those: stardot.org.uk/forums/viewtopic.php?t=19802
Hi, I have a little doubt, the Eprom programmer at your disposal supports chips up to 64k, while the chip to be programmed is 128k ...
Up to 64kBytes probably. The chip was 128kbits, which is only 16kBytes.