Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!interlan.InterLan.COM!interlan.interlan.com!yetsko From: yetsko@interlan.interlan.com (Mike Yetsko) Newsgroups: comp.sys.tandy Subject: Re: Coco software & 1000 mem upgrades Message-ID: Date: 20 Nov 90 15:27:00 GMT References: <1990Nov19.201218.12156@infonode.ingr.com> Reply-To: yetsko@interlan.interlan.com Organization: Racal InterLan, Inc., Boxborough, MA (1-800-LAN-TALK) Lines: 19 In-reply-to: fordke@infonode.ingr.com's message of 19 Nov 90 20:12:18 GMT Tandy 1000 memory is a very complicated issue. If you mean the original 1000, they had 128K on the main board that was dualmapped to the video and to a programmable window from 0-640K. Your first memory board MUST have DMA, as the machine didn't have it to begin with, and the BIOS assumes DMA is installed if it sees a memory addon. The addon memory installed at 00000 and the internal momory had its address adjusted to sit immdeiately after whatever memory it finds on the bus. This basically boils down to the fact that you need a Tandy memory card (or at least a card designed for the Tandy 1000) for your first memory upgrade. Since the newer boards go to 512K anyway, it's a moot point, but if you have old memory cards lying around, you 'could' put in a 256K Tandy memory card, then a PC generic memory card from 40000-7FFFF, and it would work. Later 1000 machines changed from this somewhat, as some used 256K as the base on-board memory, or even came full up with DMA. You should be more explicit in what machine you are working with. Mike Yetsko