weird old ROM chips...
DJ Delorie
I started working on restoring an ancient computer (Wang 2200E). Having
dealt with this computer before, I decided it would be prudent to read
out the ROM chips in case they need to be replaced again. However,
these chips don't match anything I've ever heard of. Most annoyingly,
there is no ground pin! There are 23 of these on the board, with no
inked numbers the same.
The pinout is as follows:
+5V 1 24 OE1
A0 2 23 D0
A1 3 22 D1
A2 4 21 D2
A3 5 20 D3
A4 6 19 D4
A5 7 18 D5
A9 8 17 D6
-12V 9 16 D7
A8 10 15 A10
A7 11 14 OE2
A6 12 13 nAR
Look familiar to anyone?
John Robertson
Interesting! "Fascinating"
Well, the 17VDC indicates the devices are MOS - I'd look into old
Rockwell parts from the mid-70s.
Any date codes on any ICs on the motherboard? If you can identify the
year then you can use the IC Master catalog from that year to find who
made ROM that were 1K X 8. I checked the 1978 guide and couldn't find
any likely suspects, but perhaps you will have more luck searching a bit
more through.
John :-#)#
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John Robertson
OK, I see the Wang 2000E/F was produced in January 1976, so check out
the IC Master for 1975 (assuming you can find one) or earlier for the ROM.
What do you mean by pin 13 "nAR"? No Connection visible? Did you do a
resistance check to common in case they used an early multi-layer PCB
and the ground plane is invisible by being in the middle plane?
DJ Delorie
Looks like 1978-1979 time period.
http://www.delorie.com/tmp/wang2200E-roms.html (280 KB)
(yes, the pins are *rusty*)
> If you can identify the year then you can use the IC Master catalog
> from that year to find who made ROM that were 1K X 8. I checked the
> 1978 guide and couldn't find any likely suspects, but perhaps you will
> have more luck searching a bit more through.
That doesn't sound like something that would have ended up online...
DJ Delorie
John Robertson <sp...@flippers.com> writes:
> What do you mean by pin 13 "nAR"? No Connection visible? Did you do a
> resistance check to common in case they used an early multi-layer PCB
> and the ground plane is invisible by being in the middle plane?
The schematics labelled that pin AR with a bar over it. I suspect it's
"address ready".
DJ Delorie
John Robertson <sp...@flippers.com> writes:
> OK, I see the Wang 2000E/F was produced in January 1976, so check out
> the IC Master for 1975 (assuming you can find one) or earlier for the
> ROM.
As for the year discrepancy, note the "in case they need to be replaced
AGAIN" in my original post ;-)
If the power supply loses a rail, the ROMs are the first chips to die
from it :-P
John Robertson
Ah, thanks, the picture helps. Certainly the date codes are from 77
through 79. The manufacturers logo "E/A" looks familiar. I'll have to
check that tomorrow in my IC Masters if I have time...figuring out the
manufacturer should enable us to find the part number.
These are masked ROMs of course.
DJ Delorie
Of course. I was hoping I could read them out and save the data at
least. If they get toasted I'll have to figure out how to create
replacements from today's technology.
Tilmann Reh
> Ah, thanks, the picture helps. Certainly the date codes are from 77
> through 79. The manufacturers logo "E/A" looks familiar.
Looks like "Electronic Arrays Inc.":
<http://www.elnec.com/support/ic-logos/manufacturer-description/?manuf=Electronic+Arrays>
<http://www.antiquetech.com/companies/EA.htm>
Tilmann
Morten Leikvoll
news:xnmxepf...@delorie.com...
Maybe this page can add some information
http://oldcalculatormuseum.com/t-wangic.html
Cant find your part#'s there but still...
Morten Leikvoll
http://home.wxs.nl/~janvdv/wang/wangmuseum.htm
Maybe you can dig deeper from there for more info.
Pages like these makes me num.. :)
DJ Delorie
Yeah, I've been though the museums some. I figured this place was an
easy first choice for finding the base part *if* it was a common part
back then, I'll try to hunt down someone who's fiddled with these parts
before, next.
Mark Zenier
If you take pin 1 as ground and pin 9 as Vcc it's the same as the
Signetics 2600 masked ROM, but that's an NMOS part (circa 1978) that runs
on +5 volts. A couple GI ROMs from 1977 also use pin 1 and 9 as gnd/vcc.
And other GI parts use +5/-[some voltage] as "ttl compatible" PMOS.
So this is a PMOS part from several years earlier. The Signetics sheet
cross references EA4600 and EA4900. Electronic Arrays, as I remember.
Mark Zenier mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
DJ Delorie
mze...@eskimo.com (Mark Zenier) writes:
> If you take pin 1 as ground and pin 9 as Vcc it's the same as the
> Signetics 2600 masked ROM, but that's an NMOS part (circa 1978) that runs
> on +5 volts. A couple GI ROMs from 1977 also use pin 1 and 9 as gnd/vcc.
> And other GI parts use +5/-[some voltage] as "ttl compatible" PMOS.
>
> So this is a PMOS part from several years earlier. The Signetics sheet
> cross references EA4600 and EA4900. Electronic Arrays, as I remember.
Thanks for the info. /me wishes stuff back then was on the Internet
already :-P
John Robertson
If you can access the data and address bus directly you could always
read the entire bank of ROM using something like a Fluke 9010 or 9100
(if the CPU is common) or even wire up an adapter so you could connect
to an Eprom reader. Schematics would help for this project!
John Robertson
That's a help - it certainly matches the age and logo. Now DJ can post a
note here - something like: Subject: Electronic Arrays ROM data book
needed...
DJ Delorie
John Robertson <sp...@flippers.com> writes:
> If you can access the data and address bus directly you could always
> read the entire bank of ROM using something like a Fluke 9010 or 9100
> (if the CPU is common) or even wire up an adapter so you could
> connect to an Eprom reader. Schematics would help for this project!
Thought of that already. I have plenty of embedded MCU boards with
enough I/O to watch the whole address/data bus, if I dared power it up.
I'd rather read them *before* risking them. The other trick would be
getting the computer to cycle through all the addresses.
Ian Field
Dead easy (peek/loop etc) in basic - just literally a few lines.
Just a few more lines to open/copy/close a disk file.
DJ Delorie
"Ian Field" <gangprob...@ntlworld.com> writes:
> Dead easy (peek/loop etc) in basic - just literally a few lines.
You're assuming this computer's basic has instructions for reading the
40-bit-wide ROM space, which may not share a data path with the
8-bit-wide RAM space. This machine has no MCU chip - it's all
implemented in SSI and MSI logic gates.
> Just a few more lines to open/copy/close a disk file.
The disk format is also not compatible with anything else.
Heck, if this were easy, I wouldn't need help, would I ;-)
petrus bitbyter
"Ian Field" <gangprob...@ntlworld.com> schreef in bericht
news:OZw8q.4866$4X4....@newsfe27.ams2...
Don't think so. The number of ROMs make me think they do not contain a
monitor program but the microcode of the processor. I've seen more old
machines functioning this way. Most pre PC minicomputers did so. I like to
see the schematics if possible. They *may* give enough information to find
out how the chips have to be operated. For instance do you need to provide
12V before +5V or the other way around? Doesn't it matter? Should they be
there at the same time? As they have no external 0V reference, do some other
connected chips provide it? As there apparently is no spare available, these
questions need to be answered before a reliable interface can be build to
read these old boxes.
petrus bitbyter
Ian Field
"petrus bitbyter" <petrus....@hotmail.com> wrote in message
news:4e640242$0$5077$e4fe...@dreader17.news.xs4all.nl...
>
> "Ian Field" <gangprob...@ntlworld.com> schreef in bericht
> news:OZw8q.4866$4X4....@newsfe27.ams2...
>>
>> "DJ Delorie" <d...@delorie.com> wrote in message
>> news:xnbov1e...@delorie.com...
>>>
>>> John Robertson <sp...@flippers.com> writes:
>>>> If you can access the data and address bus directly you could always
>>>> read the entire bank of ROM using something like a Fluke 9010 or 9100
>>>> (if the CPU is common) or even wire up an adapter so you could
>>>> connect to an Eprom reader. Schematics would help for this project!
>>>
>>> Thought of that already. I have plenty of embedded MCU boards with
>>> enough I/O to watch the whole address/data bus, if I dared power it up.
>>> I'd rather read them *before* risking them. The other trick would be
>>> getting the computer to cycle through all the addresses.
>>>
>>
>> Dead easy (peek/loop etc) in basic - just literally a few lines.
>>
>> Just a few more lines to open/copy/close a disk file.
>>
>
> Don't think so. The number of ROMs make me think they do not contain a
> monitor program but the microcode of the processor. I've seen more old
Most of the external microcode units I've seen had piggyback receptacles on
top the CPU for plugging a ROM into.
petrus bitbyter
I know them too but the processors I'm talking about are build of bitslices
or lower intergrated logic. They're not only pre PC but even pre micro.
petrus bitbyter
josephkk
Ah yes, 2900 (TTL), COSMAC, and the likes. And there were a lot of
hybrids as well with the micro doing the "slow" stuff.
?-)
Franc Zabkar
put finger to keyboard and composed:
>DJ Delorie wrote:
>> The pinout is as follows:
>>
>>
>> A8 10 15 A10
>Any date codes on any ICs on the motherboard? If you can identify the
>year then you can use the IC Master catalog from that year to find who
>made ROM that were 1K X 8.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Jamie
> On Thu, 01 Sep 2011 10:03:44 -0700, John Robertson <sp...@flippers.com>
> put finger to keyboard and composed:
>
>
>>DJ Delorie wrote:
>
>
>>>The pinout is as follows:
>>>
>>>
>>> A0 2 23 D0
>>> A8 10 15 A10
>
>
>>Any date codes on any ICs on the motherboard? If you can identify the
>>year then you can use the IC Master catalog from that year to find who
>>made ROM that were 1K X 8.
>
>
> 11 address bits makes them 2K x 8 parts.
>
> - Franc Zabkar
yesteryears.
Jamie
John Robertson
PROM manual it covers the Mostek MK28000 which is a PMOS device using
-12/+5 and might well be similar or the same as yours.
Best guess for part numbers are:
EA4900C or EA4900L
Signetics has a PMOS 2K X 8 #2580 that might be close too...
Looking in my 1975 National Memory book I find the 24 pin MM4214/MM5214
(512 X 8) has a similar power layout (+5 & -12) with no ground/common
connection! The book doesn't show the wiring, but does say the PMOS
device as directly connected to TTL devices and each line has a 10pf cap.
DJ Delorie
John Robertson <sp...@flippers.com> writes:
> Looking in my 1975 National Memory book I find the 24 pin
> MM4214/MM5214 (512 X 8) has a similar power layout (+5 & -12) with no
> ground/common connection! The book doesn't show the wiring, but does
> say the PMOS device as directly connected to TTL devices and each line
> has a 10pf cap.