Path: utzoo!mnetor!uunet!husc6!psuvax1!vu-vlsi!cbmvax!hedley From: hedley@cbmvax.UUCP (Hedley Davis) Newsgroups: comp.sys.cbm Subject: Re: 1700/1750 RAM expansions Message-ID: <2943@cbmvax.UUCP> Date: 14 Dec 87 20:25:26 GMT References: <465@nuchat.UUCP> Reply-To: hedley@cbmvax.UUCP (Hedley Davis) Organization: Commodore Technology, West Chester, PA Lines: 86 Keywords: ramdisk questions 1700 1750 In article <465@nuchat.UUCP> seven@nuchat.UUCP (David Paulsen) writes: > > >I've got a 1700 RAM expansion, intended for the Commodore 128. After goofing >around with it for a few months, I've accumulated some questions I'm having >trouble getting answers for: > >1. Where can I obtain a disk emulator for the thing, so that I can SAVE and >LOAD files to/from RAM just like DOS? I had the impression that a utility like >that would come on the disk; it's really the reason I got it in the first >place. > The RAMDOS is now shipping with the 1700/1750/1764's. It has been for sometime now ( a few months ). Suggest you find a user group, or a dealer with the disk, and copy it. The binary is in the public domain. >2. I've heard that a 128K 1700 expansion cartridge can be upgraded to a 512K >1750 cartridge... true? Difficult to do? Yes, this is easy ( if the rams are not soldered in ). All you need to cut open J1, and replace all the rams with 41256-15 types. > >3. What chip is supposed to go in the "U18" location on the circuit board? >(Yes, I've already taken it apart! Bye-bye warranty...) That is for a rom. We are not shipping the unit with a rom. > >4. Can more than one 1700/1750 be utilized at the same time, via a motherboard? >What does this do to the 128's power supply? > It is our official policy that only one thing can be inserted in the cartridge slot at any time. Lots of people do not listen to us. :-) As for 1700/1750/1764s, this would be a really bad idea. The power supplied with the system is NOT sufficient to power two ram expansions. > >5. What's the difference between the 1700/1750 and the 1764, aside from the >new power supply? I have already upgraded my old 64's p.s. to a huge mutha >9A regulated bench supply... does this mean I can just plug 'er in to the 64 >without frying anything? > They are essentially identical. There is a single resistor which must be removed for use with a 64. This is R4. On a C64 R4 must be removed. On a C128, R4 must be installed. Understand that we cannot condone your power supply with our equipment. It sounds ok, but we warrent nothing with regard to that usage of your equipment. > >6. With the 1700 installed on a 128, I GO 64. From 64 mode, the MMU doesn't >let me see any of the 128's memory beyond 1 64K page... can the REC, in the >1700, even in 64-mode, see the whole 128 memory map? > No. >As far as "friendly" Ramdisk emulators, the kind that allow OPEN as well as >DLOAD and DSAVE, I've been working on one myself. It utilizes the REC's swap >capabilities to switch out chunks of the 128's RAM so it appears to the o/s >that there's very little overhead to the ramdisk software. My actual overhead >is a little over 300 bytes, allowing about 11K of "actual" ramdisk support >software to be swapped in as needed. It even works with most interrupt-driven >utilities, as long as they put the vector back where they found it, or pass >it thru... other than that, it's totally transparent. > This is how ours works, although the stats are slightly different. We use a single page for the "link" and swap about 8k of code. Our code should be transparent in the same way yours is. ( Betcha its better :-) ). >Anyone doing anything with their 1700/1750's? They seem to sell well, so people are using them for something. > >-- >David Paulsen ...uunet.UU.NET!nuchat!seven > >"Commodore VIC-20... the wonder computer of the 80's!" Hedley Davis