blgardne@esunix.UUCP (Blaine Gardner) (07/05/88)
The response to my query for information on the Great Valley Products (GVP) A2000 hard drive controller was the staggering total of 2. But there is some good information, so here they are: ========================================================================== Date: Mon, 20 Jun 88 12:45:52 edt From: uplherc!oodis01!lll-tis!lll-crg!uunet!cbmvax!daveh (Dave Haynie) Message-Id: <8806201645.AA23007@cbmvax.UUCP> To: uplherc!esunix!blgardne Subject: Re: GVP "Impact" hard drive controllers? blgardne@esunix.UUCP (Blaine Gardner): > Keywords: Great Valley Products SCSI RAM cheap any good? > GVP's "Impact" hard drive controllers combine a DMA, autoboot, SCSI hard > drive controller (no ST506) with a one or two megabyte RAM expansion > on one card. I've seen their ads in the magazines the last couple > of months, and the combination of SCSI hard drive controller and RAM > expansion on one card sounds pretty attractive. Most attractive of all > is the price. They have two models, one with space for 1M of 256K x 1 > chips, and another with space for 2M of 256K x 4 chips. The 1M contoller > lists for $325, and the 2M version for $360. It's a pretty good price, but it's also somewhat misleading. In the way the controller actually works -- I think this may be what Microbotics calls "pseudo-DMA". What actually happens is that the on-board control logic manages DMA, all right, but that DMA only goes into a 4K static RAM. In order to get data from the disk to the Amiga's memory, there's a DMA transfer between the hard disk and the GVP board, but then a CPU tranfer between GVP memory and real system memory. Even if the system memory is on the GVP board. So you end up with a system that's faster than just reading an I/O mapped SCSI port, but slower than true DMA. I haven't actually seen how this preforms with FastFilesystem against the 2090 or any other true DMA card, but it should be as much as 1/2 the speed, depending on file system overhead. The actual transfer method you get is less than 1/2 the speed of full DMA. About the only advantage of this system (there had to be one), is that you get a whole chunk of data from the disk drive locally buffered without any lags. With real DMA, you may have to wait until a horizontal retrace to complete a DMA arbitration, so there may be a lag before a transfer is started. The GVP product would still have such a final transfer lag, since it's depending on the CPU for transfer, but since the data is locally buffered, this is never a problem. On some disk systems, these lags may cause the drives to have to do a complete retry. > If you e-mail me I WILL summarize and post to the net. Sure thing. =========================================================================== Date: Mon, 20 Jun 88 07:40:15 EDT From: Kent Paul Dolan <utah-cs!ut-sally!ames!xanth.cs.odu.edu!kent> To: esunix!blgardne Subject: Re: GVP "Impact" hard drive controllers? Newsgroups: comp.sys.amiga In-Reply-To: <873@esunix.UUCP> Organization: Old Dominion University, Norfolk Va. Cc: Blaine, Before you buy an "add your own 256K x 1 DRAMs" board, make very, very sure you have a real, dependable source of those DRAMs. Preferably they should be in your hands first. I've been trying for many weeks now to chase down one (1) 256K x 1 SIP DRAM to repair my Telesoft (may its founding principles rot in Hell) RAMBOard, which has a stuck bit that prevents vd0: from recovering. The story I get is that the DRAMs are all "allocated" to satisfy existing delivery contracts, and there are NONE available for individuals to purchase. While this may not be true of the chips you need (I want an obscure Japanese import called an MT1259Z-15), I'd sure check carefully before buying an unpopulated board. Don't get burnt like I've been. Kent, the man from xanth. ========================================================================= -- Blaine Gardner @ Evans & Sutherland 540 Arapeen Drive, SLC, Utah 84108 UUCP Addresses: {ihnp4,ucbvax,allegra,decvax}!decwrl!esunix!blgardne ihnp4!utah-cs!esunix!blgardne usna!esunix!blgardne "Nobody will ever need more than 64K." "Nobody needs multitasking on a PC."