tve@cernvax.UUCP (Th.v.Eicken) (03/02/86)
The other day I wondered how a program could be efficiently loaded into expansion RAM. Remember the custom chips can only access the internal 512K and disk DMA is handled by one of these chips. If I interpret this correctly, to load a program or data into external memory requires it to be first put into internal RAM and then copied by the 68000 (!) into external RAM. Should this be correct, a 68010 would really be worth it as soon as external RAM is added. Did I overlook anything ? Thorsten von Eicken ----- Thorsten von Eicken tve@cernvax.UUCP Div. EP ...!seismo!mcvax!cernvax!tve CERN Geneva Switzerland -----
LAVITSKY@BLUE.RUTGERS.EDU@caip.RUTGERS.EDU (03/04/86)
From: dillon%cory@BERKELEY.EDU (Matt Dillon) You did. The trackdisk.device puts tracks from the disk an an intermediate 'track buffer'. Besides, you can't simply DMA a sector into memory and get valid data .... it's encoded (Which is why the Amiga disk routines are slower than comparable IBM disks.. the IBM's have real floppy controllers, the Amiga doesn't) -Matt
hr@uicsl.UUCP (03/04/86)
RE:
The other day I wondered how a program could be efficiently loaded into
expansion RAM. Remember the custom chips can only access the internal 512K
and disk DMA is handled by one of these chips.
If someone were fortunate enough to have both fast memory and
an external hard disk, would data transfers still have to go directly
into chip memory?
----
harold ravlin {ihnp4,pur-ee}!uiucdcs!uicsl!hreric@chronon.UUCP (Eric Black) (03/06/86)
> Thorsten von Eicken tve@cernvax.UUCP writes in <282@cernvax.UUCP>: > The other day I wondered how a program could be efficiently loaded into >expansion RAM. Remember the custom chips can only access the internal 512K >and disk DMA is handled by one of these chips. > > If I interpret this correctly, to load a program or data into external >memory requires it to be first put into internal RAM and then copied by >the 68000 (!) into external RAM. > > Should this be correct, a 68010 would really be worth it as soon as >external RAM is added. > > Did I overlook anything ? What you overlooked is that the expansion bus is a full 68K bus, and that any expansion device plugged onto it can become the bus master (assuming that it asks nicely). An external disk controller hopefully will include a DMA controller of its own. Using the DMA provided by the internal custom chips is probably not possible, and is not desirable. Note that DMA from the external disk to "fast RAM", e.g. for program loading, can go on completely in parallel to internal access to "chip mem", e.g. video. -- Eric Black "Garbage In, Gospel Out" UUCP: {sun,pyramid,hplabs,amdcad}!chronon!eric VOICE: (415) 941-0403 US SNAIL: Chronon Computer Corp. 2570 El Camino Real W. Suite 206 Mountain View, CA 94040