PX-8 - It's not all bad..

With my escapades ongoing with the PX-8 RAMDisk you'd be forgiven for thinking that the thing is cursed. Of course it isn't because a) it was free, nothing that is free can be cursed, and b) curses aren't real.

The PX-8 has two slots for ROMS. The ROMs fit into little carriers that I shall call pods because it sounds cool to say 'ROM pod'. So there. These pods contain additional applications to run on the PX-8 which could be anything from a word processor such as WordStar to a diary or calculator. The pods can also accept EPROMs of different capacities and this unit came with a bunch of them.

Pod, pod, pod.

Pod, pod, pod, pod, you get the idea.

The first thing to do with these is to dump the ROMs so that I can re-use the chips for other things but easily restore them to their original state if I need to. This is particularly important for the DS8 video output boxes that came with the PX8 which are probably the rarest things I currently have in my collection. (I don't know if they work but if I don't plug them in and turn them on, they might..) Reach for the Dataman S4!

I'm not sure if I mentioned but I modified the S4 to run directly from a mains adaptor by hooking up the battery terminals directly to a modern power supply. This removes the need for an internal battery which also removes the risk of a damaging leak but has the drawback I have to re-load the 'library' of supported EEPROM devices every time I want to use it. A minor inconvenience.

To get going I just boot up the Dataman software from 2003, which works flawlessly with Windows 10 if you were wondering, and just select 'Download Library'. Then I select the library file, which is still available from the Dataman website, and then wait a couple of minutes. A message 'START LIBRARY?' appears on the display and by pressing 'ENTER' everything is ready to go.

Library 3.00 ready for action

To select the correct chip type it's a simple matter of pressing 'PROM' then using the up/down arrow keys to find the right manufacturer then the left/right arrows to select the right chip. Easy peasy.

This EEPROM is a National Semiconductor.

So, what to do. I take one of the dumped EEPROM chips and a PX-8 ROM file downloaded from the most excellent resources located here and here. How do I get it on to the chip? Well, first of all this is a UV erasable EPROM so I can't clear it with the S4, I need some other way. The datasheets for EEPROMs will normally give an indication of what's required and in most cases it's a blast of UV light at a wavelength of 257nm (nano metres) for about ten minutes.

Intel D27256 EEPROM
Note the window where UV enters

I have to tell you now that the EEPROM erasers that are available on various auction and other retail sites are complete garbage. I shall quote from one review of a unit that someone purchased from a well known site:

"This is basically a 'use at your own peril' device. It's really badly made with gaps all around the base and top cover. I'm sure if Her Majesty's Customs had anything to do with this, they'd incinerate them on sight. ... although it feels as if there's a reasonable chance they would do that on their own.

The warnings that come with this are crazy; maybe because they're in broken English. The gist of it is 'turn it on, run and don't look back'.
...
Having read the other reviews , the first thing I did was take it apart and put in a new power cable and a fused UK plug. The one you're replacing is terrible - there's around 5 threads per core.
...
After leaving on for seven minutes (with an extension lead going to the device, which I sat in a bucket with wood over the top. If I had an x-ray screen I would have probably gone behind that too) it did actually blank the AMD 27C400 inside.

I didn't really doubt that it would, I just expected it to explode or at the very least start smoking as soon as I flicked the power on.

So? If you need to blank an eprom or two, then go for it, but, take enormous care with this piece of junk."

This was not what I would call a 'glowing' review.

But there is an alternative. In a bizarrely 'Hitch Hikers Guide' turn of events, I purchased a 'Phone Sanitiser'. This is basically a white box that you put your mobile phone into and, for ten minutes, it bathes your phone with UV light at 257nm, to kill bacteria and leave you with that smug feeling that you won't catch any virulent diseases while posting cat pictures on Instagram (or whatever the kids are doing these days).

You won't be wiped out by a virulent disease contracted
from a dirty telephone.

But did you see what it does? It emits 257nm light for ten minutes. And it only cost me £13. And it's a surprisingly high quality unit. There is mention of 'Samsung' on the box and in the small manual it comes with but it's not directly made by Samsung. No matter. It does what I need it to do.

Opening the lid reveals two small tubes, one at each end. By resting the EEPROM with the window directly facing the tube, it is completely erased in ten minutes. Blank EEPROMs are full of 'FF's which indicates they're ready for writing. Nice. I shall probably look at designing and 3D printing something to hold the chips more securely in sanitiser in the future. 

Open sesame..

FFs sake.

So now I have a blank EEPROM and I want to write my downloaded ROM to it. In the S4 software I just select 'Transfer > Send file (PC>S4)' and select the ROM file. The format of the file can vary, mine is a 'HEX' format, but the software supports at least four different formats.

After a minute or two the transfer is complete and on the S4 software I select 'Memory>Checksum RAM' to check what the value should be, then 'Device Pretest' which should tell me the EEPROM is blank. Then I can 'Burn' which copies the contents of the S4 RAM onto the EEPROM. Once complete I always do a 'Device>Checksum ROM' to make sure it matches the RAM checksum from earlier. 

In theory, the EEPROM should be ready for installation into the bottom of the PX-8. The little carriers aren't essential and the EEPROM can be fairly easily pressed into the socket without any problems.

Does my new ROM work?

Yes. (Sub Zone)

Yes. (Tower)

Yes. (Tank Attack)

Yes. (Snake Pit)

These are about the only games for this system (I do have a version of Othello I want to try though) and they all work perfectly and are surprisingly fun, even if my aged hands start to hurt on the cursor keys after a few minutes. 

Now, if only I could get that RAMDisk to work...