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HP 49G Advantages over 49g+ & 50g
01-24-2018, 12:32 PM (This post was last modified: 01-25-2018 09:16 AM by jebem.)
Post: #18
RE: HP 49G Advantages over 49g+ & 50g
(01-23-2018 04:12 PM)Dave Britten Wrote:  
(01-23-2018 03:28 PM)jebem Wrote:  <Question on what ERAM and IRAM means>
I'm really curious to find out... and yes, I did research before I asked here...
Thank you in advance.

I have a very faint recollection that the I and E stand for internal and external respectively. Note that these are recollections from around the time the 49G was released, so it's possible that's entirely a fabrication from my subconscious. If there's some truth to it, then I probably read it on comp.sys.hp48, though.

I thought the same way, but it seems that this is not the case.
Meanwhile I have been doing further reading here and there, and:

- I have learn that IRAM means "Independent RAM", as found on several HP-71 documents available elsewhere. The 71B was the first machine to use the Saturn processor.

- I also learned that the Saturn processor does NOT have internal RAM to store programs. Its internal SRAM is dedicated to support the CPU Registers.

- So, all the SRAM (static RAM), FLASH ROM, or SD Cards, must be External to the Saturn processor.

- The internal PCB pictures I found at HPCALC shows, among other chips:
- One TE28F160 16Mbit FLASH ROM;
- One KM684000BLT-5 512KByte SRAM.

This makes sense with what we see on the 49G File Manager information:
Model 49G (ID93406767, Indonesia, 1999, week 34)
VERSION: HP49-C Revision #1.18 HP 2000
Port 0: IRAM 241KB
Port 1: ERAM 255KB
Port 2: FLASH 1079KB
Home 241KB (that's the shared Port 0 from above)

Also, as I mentioned above in another post, while the IRAM is Volatile static RAM shared with "System RAM" and cleared by a memory clear operation, the ERAM it's not shared with "system RAM" and is not cleared by a memory clear operation.

So, it seems that despite using one single 512KByte SRAM chip shared among ports 0 and 1, each segment is handled in a different way by the calculator kernel.

And the question remains: What the ERAM acronym means?
I'm hoping that one of the HP gurus read this and give me an answer, any answer at all will be good Smile

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RE: HP 49G Advantages over 49g+ & 50g - jebem - 01-24-2018 12:32 PM

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