Speaking of artifact colours, not all IBM CGA cards are equal either, as you might know. What’s more, even though both these cards have a composite output, neither of them produce the same artifact colours as the IBM CGA does. And neither is the Paradise PVC4 in the PC20-III. I am not sure if there are any CGA clones that are cycle-exact to a real IBM though. I have another 8088 machine, a Commodore PC20-III, but it uses a Faraday FE2010 chipset instead, which is not entirely cycle-exact, not even with the real IBM CGA card installed. The 82xx-chipset is probably a feature to look out for. So there is hope: there are at least SOME clones that are cycle-exact to a real IBM. Likewise, putting the ATi Small Wonder in the 5160 made it produce the same bugs in CGADEMO and 8088 MPH as the Philips P3105. Once I swapped the ATi Small Wonder for the real IBM CGA card, the Philips P3105 machine ran 8088 MPH exactly the same as the 5160. And indeed, it turns out that the Philips machine uses (clones of) the same Intel 82xx chipset as the IBM 5150/5155/5160 (also known as the MCS-85 set, originally developed for the 8085 CPU). Now that 8088 MPH was done, I had some time to experiment with the hardware. I was already working on 8088 MPH at the time, and I knew that I had to have a cycle-exact machine. I also said that I suspected the ATi Small Wonder videocard. In that blog I said the system was not cycle-exact, since the CGADEMO showed some problems with the scroller that were not visible on a real IBM. The Philips P3105 machine I have, which I discussed in the CGADEMO blog earlier, is one of these. On the other hand, we also found out that there are indeed clones that are 100% cycle-exact to a real IBM PC. The Amstrad CPC also suffers from the issue that during its lifespan, various 6845-chips have been used, introducing incompatibilities). Some used a Hitachi HD6845 instead, which does not handle a hsync width setting of 0 in the same way (the real Motorola chips interpret a value of 0 as 16. Also, as others tried to run our demo on real hardware, we found that even real IBM CGA cards had problems with some of the CRTC tweaks, since not all IBM cards used the same Motorola MC6845 chip. Because of the time pressure, there were some things we could not finish as well as we wanted. Although we were very happy with the win at Revision, we were not entirely happy with 8088 MPH as a whole.
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