Quote:
Originally Posted by Promilus
@pandy - ZIII never reached quarter of that so ... talking about theoretical ISA throughput then showing how it was actually shitty solution due to the fact real bandwidth was quarter of that... 3rd at best. Then comes Zorro III which not only destroys EISA (being actually THE SAME KIND OF DESIGN) but reaches VLB/PCI with... theoretical bandwidth. Shame actual bandwidth is much, much, much smaller and most likely even slowest PCI in PC world (so shady 486 chipsets) can outperform it. ISA (and by extension EISA) were x86 processor buses adapted to work as expansion slots. Zorro II (and by extension Zorro III) were 68k processor busses adapted to work as expansion slots. EISA was 32bit extension of ISA which was kind of backward compatible? Zorro III was 32b extension of Zorro II which was kind of backward compatible. So... yeah. Also how many native ZII/ZIII chips were produced... ever? Most of ZII/ZIII add-ons uses ISA/PCI chips with glue logic. Also... how long typical zorro card was? :P
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True - but Amiga Zorro III implementation was mostly limited by MOS/CSG manufacturing capabilities not by architectural limitations. I agree that PCI was way better in terms of standardization than Zorro III and as such being more future proof. Length of PIC was outcome of fact that CBM accepted superiority of IBM PC market penetration - ISA was prioritized over Zorro.
Quote:
Originally Posted by Thomas Richter
Input status 1 is a regular VGA register, and it includes the information you seek. This is a standard feature. What was unfortunately less standard is to wire the interrupt output of the VGA chip to an interrupt of the ISA slot.
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Yes, you have information that V sync blank is active but to fully use it you need to determine when it starts as such you need wait and pool status for whole line (or perform some measurement - calibrate and reprogram timer and use later system interrupts hoping that it doesn't de-synchronize too much between V sync start). Obviously using this feature is PITA.