USR quad modems... (ontopic - really!)

[Allison]

>
>Subject: Re: USR quad modems... (ontopic - really!)
>   From: ard at p850ug1.demon.co.uk (Tony Duell)
>   Date: Wed, 16 Aug 2006 23:35:41 +0100 (BST)
>     To: cctalk at classiccmp.org
>
>> > a TI/USR DSP chip, which is prolly useless outside of the intended use
>> 
>> Some of the DSP's are "general purpose" -- external program
>> store.  However, since you called it a "TI/USR" part, I assume
>> it has a USR house number on it and, as such, is probably
>> a masked part.  If so, "useless outside of the intended use"  :>
>
>Unless either (a) the USB part number is just their code for a standard 
>device (HP were fond of doing this...), or (b) you can disable the 
>internal mask ROM and run it from external program store, say by changing 
>the state of a pin.
>
>Without knowing more about the device I can't possibly know if either of 
>these is the case.
>
>> > So, *if* I can get a Dynamic-RAM -> Static RAM converter board designed 
>> > for the CoCo, I could upgrade 4 CoCo3s to 512K with each modem board.
>> 
>> What's the issue *preventing* this from happening?
>> (unfamiliar with the internals of a CoCo3)
>
>The CoCo 3 is designed round a custom chip called GIME (Graphics, 
>Interrupts, Memroy Enhancement). It handles all the video side, the 
>memory mamangement (remmber the 6809 can only directly address 64K), etc. 
>Said chip outputs a 9 bit multiplexed address (designed to link to the 9 
>addres pins on 256K bit DRAMs), and the DRAM timing signals. It also 
>expects 16 bit wide memory IIRC.
>
>It's probably possible to add external circuitry to turn that back into a 
>normal 18 bit address and hang SRAM off it, but I think it's more work 
>than finding some 41256s...


Way more work!  41256s are not hard to find and some of the related 
flavours like 44256 could be used as well.


>> > Roger "Merch" Merchberger -- SysAdmin, Iceberg Computers
>> > zmerch at 30below.com
>> > 
>> > What do you do when Life gives you lemons,
>> > and you don't *like* lemonade?????????????
>> 
>> Use it to flavor your *tea*!
>
>As I commented last night, citric acid is ideal for cleaning up battery 
>corrosion from calles with alkaline electrolyte (NiCds, alkaline primary 
>cells, etc).

That or vinegar work well for cleaning up after burped nicads or some 
fool charging Alkaline (durcells and the like) non-rechargeables.

FYI: I've found some off brands of nicads that if allowed to discharge
fully may leak.  I had a few with the toshiba label on them do that.
Never seen Duracells ever do that.  So quality pays.


Allison