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