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R. Belmont
Cuckoo for IGAvania
Reged: 09/21/03
Posts: 9690
Loc: ECV-197 The Orville
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Re: 8088 mph we break all your emulators
04/09/15 11:49 AM


> Oh wow, fascinating stuff. I've never heard of a PC that does that - I guess it would
> have to be done by gating the CPU's clock line. That must have been a tricky circuit
> to get working in the first place, let alone to emulate!

Depends on the bus interface. For the 68000 it's dead easy to withhold /DTACK for an arbitrary number of cycles while the hardware being accessed does stuff (the SCSI interface on 680x0 Macintoshes does this via some gate array magic to allow reading/writing data 4 bytes at a time from the 8-bit-wide SCSI controller). Dead easy in hardware anyway, it's a PITA to emulate

Anyway, MAME in the past standardized on getting the cycle counts right, lately we've been rewriting CPU cores to be able to stop on any cycle because it keeps coming up. The FIFO in Sega Model 2 will stall the i960 main CPU if it's empty, and it'll stall the geometry DSP if it's full, for instance.







Entire thread
Subject Posted by Posted on
* 8088 mph we break all your emulators RdW 04/08/15 04:56 AM
. * Re: 8088 mph we break all your emulators Moose  04/08/15 08:26 PM
. * Re: 8088 mph we break all your emulators jonwil  04/08/15 05:44 AM
. * Re: 8088 mph we break all your emulators MooglyGuy  04/08/15 08:02 AM
. * Re: 8088 mph we break all your emulators reenigne  04/08/15 11:05 AM
. * Re: 8088 mph we break all your emulators MooglyGuy  04/09/15 11:32 AM
. * Re: 8088 mph we break all your emulators reenigne  04/09/15 11:59 AM
. * Re: 8088 mph we break all your emulators R. Belmont  04/08/15 05:07 PM
. * Re: 8088 mph we break all your emulators reenigne  04/08/15 07:04 PM
. * Re: 8088 mph we break all your emulators MooglyGuy  04/09/15 02:38 AM
. * Re: 8088 mph we break all your emulators Vas Crabb  04/09/15 06:32 AM
. * Re: 8088 mph we break all your emulators reenigne  04/09/15 05:47 AM
. * Re: 8088 mph we break all your emulators R. Belmont  04/09/15 11:49 AM
. * Re: 8088 mph we break all your emulators reenigne  04/09/15 12:06 PM
. * Re: 8088 mph we break all your emulators Olivier Galibert  04/10/15 03:22 AM

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