tschak909 Posted July 5, 2014 Share Posted July 5, 2014 Is there a way to temporarily disable SDX on the IDE Plus 2.0, so that e.g. MicroSpartaDos can be loaded from a partition, instead? -Thom Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 5, 2014 Share Posted July 5, 2014 The internal SDX can be disabled from the BIOS menu. Not quite sure but there might also be a keypress during boot - been a while since I've used mine. Quote Link to comment Share on other sites More sharing options...
tschak909 Posted July 5, 2014 Author Share Posted July 5, 2014 The emulated speed of the IDE Plus 2.0 in Altirra is insane, I'm getting 54540 B/s writes, 63337 B/s reads. sheesh. Is there anything _faster_ ? -Thom Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 5, 2014 Share Posted July 5, 2014 The limiting factor is that it uses PIO - the CPU has to read/write to the data register to perform the IO. Some extra speedup could be achieved if the loop was unwound a bit, IIRC it uses a single (inx),Y instruction inside the loop, so speeds on real hardware are generally 25-70 K/sec or so depending on media and how much graphics DMA is slowing it down. Of course the ideal would be DMA but the default architecture of the XL/XE doesn't really allow for it. Anything faster? I think there might be. Some HDD interfaces present a sector buffer that appears in the IO space which would allow somewhat faster transfer speeds, or in fact just displaying directly from the buffer - IIRC phaeron did a video program that does just that. Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted July 5, 2014 Share Posted July 5, 2014 (edited) No faster, but you should get roughly the same bandwidth using Incognito or Ultimate 1MB PBI/SIDE. The reason these reads are so fast, BTW, is that the sectors are unbuffered (aside from any buffers DOS uses when not in burst mode). At c.65KB/s, the sole limiting factor is the rate at which the 6502 can pull the sectors out of the IDE controller. Phaeron overcame this by using Antic DMA instead of the CPU to read the data register. Regarding loop unrolling: the designers were aware of the concept, and IDE plus, Ultimate/SIDE and Incognito all already use loop unrolling (by a factor of sixteen, IIRC), so there is very little scope left for speeding things up. Edited July 5, 2014 by flashjazzcat 1 Quote Link to comment Share on other sites More sharing options...
+David_P Posted July 5, 2014 Share Posted July 5, 2014 Regarding loop unrolling: the designers were aware of the concept, and IDE plus, Ultimate/SIDE and Incognito all already use loop unrolling (by a factor of sixteen, IIRC), so there is very little scope left for speeding things up. ...until we get a faster CPU... Quote Link to comment Share on other sites More sharing options...
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