HP-41 and Hepax Filesystem

[Ángel Martin]

(02-07-2020 11:35 AM)pablo2000 Wrote:  Many thanks to both of you - some useful stuff in there, although I was already aware of much, but by no means all, of it.

The key information I'm after is this bit ->

(02-06-2020 04:07 AM)Sylvain Cote Wrote:  HEPAX file header uses 10 bytes
HEPAX data record use 6 bytes

I can reverse engineer it if I have to, but it strikes me as odd that a module as revered, almost a cult following, as Hepax has so little publicly available information. And believe me, I've trawled all the old publications, forums and corners of the internet! It may help if I share a little of the purpose for it. Apologies if this is a little long.

Probably the lack of information available is due to two factors: the completeness of its function set and functionality on one hand, and on the other the late date in the game it was introduced (and relative high price), limiting a widespread adoption by the community.

Not sure this is still interesting but I've checked my notes on the file HEPAX file system and found this on the headers:

File headers are located atop the file. They are sequentially accessed by HEPDIR and all other filesys operations

The file headers have 14 words, as follows:

First word (lowest address): File type (1: program, 2: Data, 3: ASCII, etc...)
Next 6 words: compressed file name, up to 7 chars long
Next 2 words: File size in registers (for programs) and words (for other types)
Next 5 words: unknown purpose.

ASCII files have an EOF word a the very bottom, value "0FF"

FileSys Info

The control area is located at 0xpFE7 - 0xpFF3.
Fields are as follows:

0xFE7 : Previous HRAM page id# (aero if first)
0xFE8: Next HRAM page id# (zero if last)

0xFE9-A: next available address . Initial value = 091 / 000

0xFEB-C: current file address , Initial value - 000 / 000

0xFED-E: first file address. Initial value 091 / 000

0xFEF-F0: last file address . Initial value 091 / 000

0xFF!-2: bottom of RAM in this page. Fixed values= 0E5 / 00F

0xFF3: initialized flag. Initial value = 100, changes to 200 after initialization

================================

Looking forward to seeing this project develop further, looks like a wonderful design!

ÁM

[Sylvain Cote]

(02-09-2020 06:54 AM)Ángel Martin Wrote:  File headers
The file headers have 14 words, as follows:

...
Same discovery here
...

(02-09-2020 06:54 AM)Ángel Martin Wrote:  Next 2 words: File size in registers (for programs) and words (for other types)

For data file there is an adjustment that I have not found why, the formula for a data file of 10 registers is:
(10 registers * 6 compressed data record) + 5 (unknown or do not remember why) = 65 = 000 041 => for first file in memory [8098 041] [8099 000]

(02-09-2020 06:54 AM)Ángel Martin Wrote:  Next 5 words: unknown purpose.

Next 2 words : unknown purpose.
Next 2 words : Next record number (for data file)
Next 1 word : unknown purpose.

[Ángel Martin]

(02-09-2020 02:08 PM)Sylvain Cote Wrote:  

(02-09-2020 06:54 AM)Ángel Martin Wrote:  Next 5 words: unknown purpose.

Next 2 words : unknown purpose.
Next 2 words : Next record number (for data file)
Next 1 word : unknown purpose.

This makes sense, i.e. having the pointer data in the file header - pretty much like the X-Mem files use the first register to hold those control fields.

Good catch, we're one step closer to the "Total Deciphering" ;-)

[Diego Diaz]

Hi Pablo, all,

Seems I'm a bit late to the party (busy dealing with my definitive retirement bureaucracy).

First of all, congrats on this nice job, Pablo!

It's amazing that 40+ years after this great calculator was first available so many improvements both HW & SW are still being developed to increase its (already outstanding) original functionalities.

Looks like our small enthusiasts community is both active and dedicated to keep these nice machines alive for many years to come.

Good news indeed!

Best from Canary Islands.

Diego.

[pablo2000]

Hi all

Sorry I’ve been off the air for a little while - we got hit by a pretty big storm and when the power company got the lights back on, local flooding had trashed all the cable companies equipment at street level. Water and internet don’t play real well together, apparently!

Thanks so much for the file header info.... will save me a ton of reverse engineering.

I’ll post again in the morning after I’ve had a chance to play with the info. But finding it here waiting for me put a big smile on my face after getting things up and running again!

P

[Mark Power]

Hi Pablo,

Fabulous project. Well done!

Put me down for one as soon a you have them in production.

Mark

[Allen]

Pablo,
This is a very impressive project!! Nicely done!

Do you plan to do a limited production run?
Best,
Al

[MeindertKuipers]

Just wondering about the status of this project. I am really interested to find out what's inside, and out of other interest would be interested in both the housing and the HP41 module connector solution, let's say for a possible other project

[Ángel Martin]

(08-18-2020 12:50 PM)MeindertKuipers Wrote:  Just wondering about the status of this project.

Same here... hopefully it's not mothballed for good...

[Massimo Gnerucci]

Many of us are waiting for news about it.

[JurgenRo]

(02-08-2020 10:34 PM)Guenter Schink Wrote:  

(02-08-2020 10:31 AM)PeterP Wrote:  Awesome project! Sign me up as a customer and guinea pig!

Cheers

PeterP

+1

Günter

+1

Juergen

[Sylvain Cote]

(08-18-2020 06:05 PM)Massimo Gnerucci Wrote:  Many of us are waiting for news about it.

Yep!