What chips does the TRS-80 Model I use for video memory?
John McCormick
I have a M1 that seems to need it's video memory replaced. Also what memory
chips were used for the 16k in the keyboard unit? I could look in the
computer but I figure by the time I can get the thing out of the box and
opened up I could have a response and have gotten the chips already.
Ron Cook
John, I donated my Model 1 to a Boy Scout Troop several yeras ago but
I seem to recall the chips are 120ns 4116s.
Ron
On 4 Dec 1996 19:36:59 GMT, "John McCormick" <a-jo...@microsoft.com>
wrote:
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10254...@compuserve.com
fax: 617-231-0261
ct...@magiclink.com
In <01bbe21a$8e36be40$b479399d@a-johnmc2>, "John McCormick" <a-jo...@microsoft.com> writes:
>I have a M1 that seems to need it's video memory replaced. Also what memory
>chips were used for the 16k in the keyboard unit? I could look in the
>computer but I figure by the time I can get the thing out of the box and
>opened up I could have a response and have gotten the chips already.
>
John,
The video section uses 2102 static rams (1k 1bit) you can order them from
JDR Micro Devices 1-800-538-5000.
The DRAM, if it is a 16k model is 4116-200ns (16k 1bit) (+5, +12, -5 vdc).
I don't remember what the 4k chips were.
Chuck Todd
at Warp with Speed Pascal/2
Shawn Sijnstra
Well... the model I uses 2102 static RAM chips for video memory (7 of them
unless you have a lower case mod.) I think they were designated 21L02 at
some stage. The main ram is 4116 dynamic ram. 8 of them. If you want to
substitute larger rams that fit in the same socket, bear in mind that
the 4116 uses nasty voltages that would do serious damage. You also have
to remember that the 4116 requires only a 128 cycle refresh. Most of the
newer larger RAMs require 256 cycle (4164 and 41256) although you can
get the 4164 at the same refresh. It is useful to replace the built in
RAMs with 4164s. It consumes less power, simplifies power supply (although
floppy disc controller is a problem), and gives you 48k on board which would
run at triple speed. Hope I haven't given you too many pointless facts.
Shawn
Shawn Sijnstra
I doubt the chips were 120ns. More likely 200ns or slower. The custom TRS80
explains it all... even down to the pre-1979 RAMs that had a mind of their
own. (slow beta radiation from the substrate changed bits at random). I think
the model 4 came with 150ns chips as standard, and the model I went as low as
350ns (feel free to correct me).
Shawn
ric...@warwick.net
John McCormick (a-jo...@microsoft.com) wrote:
: I have a M1 that seems to need it's video memory replaced. Also what memory
: chips were used for the 16k in the keyboard unit? I could look in the
: computer but I figure by the time I can get the thing out of the box and
: opened up I could have a response and have gotten the chips already.
I think the video memory was 2002's, and the main memory was 4116's.
(Unless it's a 4K machine, of course.) I haven't seen a 4116 on sale
in ages.
What makes you think the video memory needs replacing?
Francesco Micale
If memory serves, the m1 used 21L02 static RAM chips for the video memory. They're
1K by 1 devices, that I doubt are still available. Your best bet is to try JDR
microdevices, or Jameco. They may still have a few stuck under a filing cabinet, or
something. If they don't have the memory, you might have to consider getting a
"parts" computer.
best regards,
Frank
Tom Lake
Actually the 4116's were 16Kx1 used for the main memory. Video memory used
seven 1Kx1 chips (you could get the eighth chip installed with a lowercase upgrade)
I don't know the part number on the video memory chips but if you open the
case, you can read it off them. When you find out what they are, check JDR Microdevices
at 1-800-538-5000 or check their Web site (I don't have the URL right now but try
http://www.jdr.com
Tom Lake
Bill Buzbee
John McCormick (a-jo...@microsoft.com) wrote:
: I have a M1 that seems to need it's video memory replaced. Also what memory
: chips were used for the 16k in the keyboard unit? I could look in the
: computer but I figure by the time I can get the thing out of the box and
: opened up I could have a response and have gotten the chips already.
The 16k in the keyboard are 4116's (16k x 1 bit), and the video
memory are 2102's (1k x 1 bit). You can order these from Jameco
Electronics, http://www.jameco.com
..Bill Buzbee
John McCormick
> I think the video memory was 2002's, and the main memory was 4116's.
> (Unless it's a 4K machine, of course.) I haven't seen a 4116 on sale
> in ages.
>
> What makes you think the video memory needs replacing?
>
I know that the video memory is bad because when I start the machine a
majority of the display is OK but many of the video characters that should
be spaces are $'s. If I type a character where the $'s are the $ changes to
another character but it seems a bit is stuck on.
Javier Henderson
In comp.sys.tandy Tom Lake <tom...@slic.com> wrote:
> Actually the 4116's were 16Kx1 used for the main memory. Video memory used
> seven 1Kx1 chips (you could get the eighth chip installed with a lowercase
> upgrade).
> I don't know the part number on the video memory chips but if you open the
> case, you can read it off them. When you find out what they are, check JDR
> at 1-800-538-5000 or check their Web site (I don't have the URL right now
> but try http://www.jdr.com
The video memory chips were 2112 (1 x 1).
David J. Pittella
I just thought I would add my .02 ....
I think everyone was close ... the video ram chips were type 2102, we used
to call them 2102's ... and yes they are 1K x 1 static ram chips.
The advice to check the chips is sound, I don't remember what speed they
were.
The speed is designated by the number after the dash (example 2102-3).
There is also a type 21L02, the L stands for low power, these will also
work
on the Model 1 logic board.
David J. Pittella
Javier Henderson <jav...@kjsl.com> wrote in article
<589iko$juc$3...@mate.kjsl.com>...
James Cameron
John McCormick wrote:
> I know that the video memory is bad because when I start the machine a
> majority of the display is OK but many of the video characters that
> should be spaces are $'s. If I type a character where the $'s are the
> $ changes to another character but it seems a bit is stuck on.
You say "many" of the spaces are instead "$". This is a single bit
alteration, as you say. My question: is it "all" the spaces, i.e. is
a "cleared" screen a screen full of "$"? If so, then I'd suspect the
entire chip for the third bit position, and also the character
generation ROM and the PCB paths to and from it and the RAM chip.
I have successfully piggy-backed a 2102 chip over an existing one just
to prove the problem is cured before I fight it with the soldering
iron or the chip puller. Finger pressure was enough.
--
James Cameron
Digital Equipment Corporation (Australia) Pty. Ltd. A.C.N. 000 446 800
(cam...@stl.dec.com)