Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!bagate!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: Hardrives and the A3000 Message-ID: <20262@cbmvax.commodore.com> Date: 2 Apr 91 15:31:40 GMT References: <1991Mar19.222827.16244@en.ecn.purdue.edu> <17727@crdgw1.crd.ge.com> <1991Mar20.220547.4677@en.ecn.purdue.edu> <20023@cbmvax.commodore.com> <4216.tnews@tower.actrix.gen.nz> <20249@cbmvax.commodore.com> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 34 In article <20249@cbmvax.commodore.com> jesup@cbmvax.commodore.com (Randell Jesup) writes: >In article <4216.tnews@tower.actrix.gen.nz> johnv@tower.actrix.gen.nz (John Veldthuis) writes: >>Quoted from <20023@cbmvax.commodore.com> by daveh@cbmvax.commodore.com (Dave Haynie): >>Can someone please explain how to use the MASK value. The documentation on >>it is very scimpy. >>I have an A2620 in my Amiga and I have lockup troubles when DMA'ing to 32 >>bit memory with my HardFrame Harddisk and want to set the MASK so that the >>HardFrame only uses the 4 meg of Fast memory starting at $00600000 as >>buffers > There was some motherboard/2630 issue like this, perhaps it affects >2620's as well (dave?) A pullup or some such if my vague recollection is >right. There are actually two potential problems. An unknown number of A2000 motherboards prior to Revision 4.5 have a particular brand of buffer chip in one location between local and expansion buses that causes a marginal condition to exist for a short during DMA handoff. Most 32 bit memory systems, being faster, can see this condition as the start of a valid memory cycle. This is cured by adding a 1K resistor between pins 11 and 20 of U605 in the A2000, and it's the way we fixed it in production. It's OK to do regardless of whether or not you have this particular manufacturer's part, so anyone with DMA troubles involving 32 bit RAM on such motherboards should consider this update. Early Hardframes also had a problem, essentially a marginal bit of timing on their DMA handoff logic, nothing off enough to affect the slower 68000, but trouble for any coprocessor board with fast onboard memory. Microbotics has a fix for this, if you have one of the older boards. -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "That's me in the corner, that's me in the spotlight" -R.E.M.