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URAM: What is it? - jebem - 06-26-2014 01:01 PM
Several HP calculators from the 80's are referencing the URAM expression in the self tests, besides the DRAM (Dynamic RAM) and ROM (Read Only Memory) tests.
This is seen in the HP Pioneers series for instance (HP-27S, HP-42S, ...).
Does anyone knows what HP did mean with this URAM expression?
I work with computers since the end of the 70's and I confess that I never saw such URAM expression documented anywhere. But i do remember to work with PROM, EPROM and EEPROM technologies.
If this is the Flash technology, why not call it just FlashROM? Because it is not Flash... but it seems to be some sort of non-volatile modifiable memory of unknown technology.
Meanwhile a small research shows that URAM can be related to what they call as Unified Random Access Memory, for instance this site here.
"URAM is composed of a single memory transistor, which must be of the smallest cell size. It can perform nonvolatile functions or high-speed operations according to the set of operational biases. In other words, circuit designers can specify URAM to be Flash memory or DRAM in order to comply with their specifications."
Now, these are new technologies in constant evolution, and the articles I can find are marked with recent dates (2008 and after).
It is amazing that HP was using some sort of the same technology in the 80's... or maybe HP is using this URAM expression with a different meaning.
So, can we conclude that these 80's HP calculators uses persistent modifiable memory besides the DRAM and non-modifiable ROM memory?
What kind of objects goes into this URAM then?
EDIT:
I was checking this popular Lyuka site and it seems that the URAM can be just a 27C256 EPROM...?
RE: URAM: What is it? - Christoph Giesselink - 06-26-2014 04:23 PM
(06-26-2014 01:01 PM)jebem Wrote: This is seen in the HP Pioneers series for instance (HP-27S, HP-42S, ...).
Does anyone knows what HP did mean with this URAM expression?
The High End Pioneers like the HP-27S and HP-42S use the 1LR2 Lewis chip. Among the Saturn core, this chip contain also a display RAM. The display RAM is memory mapped I/O, but from design not all RAM cells have a connection to the display. So some of these RAM cells are used as normal RAM the others to control the pixel in the display. This RAM is called URAM.
In opposite the external 8KB RAM chip in these calculators is called DRAM.
RE: URAM: What is it? - jebem - 06-26-2014 08:58 PM
(06-26-2014 04:23 PM)Christoph Giesselink Wrote:(06-26-2014 01:01 PM)jebem Wrote: This is seen in the HP Pioneers series for instance (HP-27S, HP-42S, ...).
Does anyone knows what HP did mean with this URAM expression?
The High End Pioneers like the HP-27S and HP-42S use the 1LR2 Lewis chip. Among the Saturn core, this chip contain also a display RAM. The display RAM is memory mapped I/O, but from design not all RAM cells have a connection to the display. So some of these RAM cells are used as normal RAM the others to control the pixel in the display. This RAM is called URAM.
In opposite the external 8KB RAM chip in these calculators is called DRAM.
Thanks for the enlightenment!