Q&A with Dr. Dave Bradley
Start of the exchange
At 04/05/2025 Dr. Bradley Wrote
I would be happy to answer any questions I can about the Datamaster. But it's been nearly 50 years and I have no documentation. I was there at the beginning and can tell you why certain things were done. I was involved completely with the BIOS and reviewed large amounts of the BASIC and Diagnostics for the machine, but I don't think I can answer anything very specific.
For instance, there is a 3-key sequence in Datamaster that will invoke a simple debugger. I don't know whether that made it into the final production, or even which three keys did it. But that is the origin of Ctl-Atl-Del on the IBM PC. In fact, the answer to almost any question of "why did the IBM PC do it this way?" can be answered "Datamaster."
About component relabeling
I have some questions about this machine. Since we got at home our first System/23 I have been studying the motherboard and the keyboard, and therefore I have some questions nobody but the developers can answer. The Datamaster is a very misterious machine, but this obscurity has played against it in the long run and for this reason not so many units remain, from those even less are working. And so comes my first question: Do you know why this computer's components were relabelled? The truth is that it goes against the doctrine of using the standard parts they used. I have seen also relabelled parts in an AS/400 though.
At 21/05/2025 Dr. Bradley answered
I don't know directly why the parts are relabeled, but I have a guess. IBM certified their vendors, and this was true of common components. IBM certified the processes by which they were made, and probably asked that components made on this verified process be labeled as such -- hence, relabeled parts. This was probably done for all parts destined for IBM. I think.
About the ROM memories corruption
Then there is one of the main reasons a Datamaster can fail, which are the ROM memories. They tend to corrupt very easily and it is very easy to see Datamasters with broken romsets. For example, if you looked at the Wikipedia, the main image of the computer shows a 5322 with the 12h error on the POD screen. Those memories were sourced from Motorola and Mostek. Wouldn't you know by any chance why those memories were selected from them instead of other ROM makers?
At 21/05/2025 Dr. Bradley answered
Motorola and Mostek were probably selected from a bidding process, with their components verified. I doubt that a 50 year lifetime was part of the validation process.
About components from the Datamaster present in the PC prototype
Other than the Datamaster, I would also like to talk about the PC prototype (not the final product) and its relation with the System/23. I have two questions about it. I saw the power supply connector was maintained from the Datamaster to the prototype, but was replaced in the final product, although the signals are the very same. Do you know what was the main motivation to replace it? Then, there is the DRAM matter. I saw in the prototype that the memory used in the prototype was the 4332 (also used by the Apple III), pin-compatible with the 4132 that the Datamaster employs (I was able to determine it when studying the 64KB memory card). However the final product used its predecessor, the 4116. Does this reversion have to do with the release of the 4164 as a way to close distance between both chips trace layout?
At 21/05/2025 Dr. Bradley answered
the prototype was put together with Datamaster leftovers and whatever new components were necessary (8088, obviously). The PS and connector was one of those. Why it changed I don't know, although it may have been a space issue. Narrow connector along the side of the board rather than the fat one elsewhere? Don't really know. As for RAM, the prototype board has two banks of 32kb, while the final board has 4 banks of 16kb -- so we could sell a 16kb stripped version for an advertisable low price. That's why you have 4332s on the proto and 4116 on the final -- 32kbits vs 16kbits.
The key combination you stated was the precursor to Ctrl-Alt-Del wouldn't be by any chance Command-Test-Erase? This is a well known combination in the Datamaster but haven't noticed before how similar both combinations are.
At 21/05/2025 Dr. Bradley answered
I don't recognize any of those keys on the s/23, but it's been 50 years, and I've spent all of that time looking at the IBM PC keyboard. And C-A-D.