These projects document the reverse engineering and CPLD or FPGA based recreation of the IBM 5170 PC/AT, preserving original system behavior using modern hardware.
The historic PC development started with IBM creating the PC, the XT and the IBM 5170 PC/AT, and the 5162 system which is a follow up design of the 5170 built into a XT 5160 case.
After producing the extremely successful 5170 PC/AT, IBM attempted to move their strategy back into closed architecture that was not openly accessible for other manufacturers. However in the mean time, the computer industry took a big lesson from the amazing architecture that the IBM PC team under leadership of Don Estridge created. After the release of the IBM 5170, various early AT models in “discrete” form were created by manufacturers such as NCR and ARC. The IBM XT was also mass produced by other manufacturers, further powering the hardware and software momentum to mass produce early PC systems. But since IBM branched off into closed architecture systems, the PC industry was left with the decision of how to proceed into the future. So there was a very important follow up development for example done by Compaq to show other manufacturers the potential to take the PC evolution further, independently from IBM from then on. By creating a closed architecture, IBM basically cut off the entire PC industry which in history has proven to have been one of those events having a huge influence on the future.
Compaq, later merged into HP, in the early days has done pioneering work to clean room reverse engineer the IBM PC BIOS ROM, so their new BIOS was able to perform the same functions necessary to be fully IBM PC compatible in terms of software and hardware to be able to fully function on a Compaq PC system. This development was very important because a PC BIOS is particularly complex and needs to support many functions which are linked to specific locations in the ROM code. So any replacement ROM would need to observe many entry points in specific ROM address locations, which limit how much code could be created in which area of the ROM.
An example of historically important work was again done by Compaq, specifically by designer Paul R Culley, who designed one of the first 32 bit models of a PC/AT system, the Compaq Deskpro Model 40. This work was extremely significant because this historic brilliant design demonstrated in a working model how the PC/AT could be further developed and enhanced with a 32 bit Intel CPU, the 386DX.
The Compaq Deskpro Model 40 combined a much faster next generation 32 bit CPU using 32 bit system RAM with the existing PC/AT 16 bit bus, which although it did limit the throughput to the VGA controller on a 16 bit VGA card, it was still a really important step in the PC manufacturing industry to evolve the industry PC system further. It was a big step forward in the evolution of the “open” PC architecture powered by various manufacturers. Combining the PC/AT 16 bit bus with a 32 bit CPU is no small task because there are many types of CPU interactions with 8 and 16 data bit wide devices that need to be translated to match up with the correct byte connections to allow the 32 bit CPU to correctly perform the data transfers in all possible situations that will occur.
So the IBM 5170 and Compaq Deskpro are both big parts of the work that is currently ongoing.
I have fully reverse engineered the IBM 5170 already and recreated this technology in 4 generations of designs which are all fully functional.
The work on the Compaq Deskpro Model 40 based on the Intel 386DX CPU is currently in progress as well.
I have also done some work based on the VLSI TOPCAT integrated PC/AT chipset, however that is based on existing stock of the VLSI VL82C320 and VL82C331, which will eventually run out so these systems can be rebuilt only based on the stock of chips that is still available.
It’s also a note to consider, any designs based on programmable logic such as CPLDs and FPGAs, after the REV2 of the 5170 based development, will be created to support EMS RAM which should allow all of these to run the RealDOOM project game which uses EMS RAM.
Since I am only one person, I would welcome anyone who would like to contribute and cooperate in this effort. The more help I have, the faster things will move forward which can benefit the entire effort.
I hope this short piece of computing history of our current civilization may inspire others to join my effort and get in touch to help the preservation efforts!
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The content here will all be based on mutual respect, respectful consideration of what you want to share, and especially civilized communication. Helping the efforts here is welcome in many ways including to post messages into the project threads. If you have questions, feel welcome to post them here!
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Kind regards,
Rodney