From: <[EMAIL PROTECTED]> Subject: Re: Soft "rom" question Date: Mon, 2 Aug 2004 21:31:03 -0500
The nature of work I do for a living allows me access to a wide variety of electronic components. I also have the ability to burn just about any chip made. I find this topic fascinating and if there really is demand for this I would love to offer my help.
If you could give me a specific module form factor, rom size and maybe a few manufacturer parts numbers off the chips I bet I could come up with something. Nothing is too esoteric, If it was made Im willing to wager I can find it.
I have the ROM code for the IIci stored away on disk, and I'd be happy to email it to you.
To go into a bit more detail...
I don't know what level of detail/complexity to discuss this, so I'll stay to a simple level. If this is too simplistic and covers already understood ground I apologize.
The SE/30 ROM is 128K X 32. In other words it is 32 bits (4 bytes) wide and has 128K addresses. The ROM module achieves this by using four 128K X 8 chips in parallel. So the organization of the chips on the ROM module is 128K X 8. This is a very common capacity and organization for non-volatile memory chips (Flash, EEPROM, EPROM).
The problem is that capacity and organization are not the only parameters of a memory chip. Another factor is the package. The package is the physical body in which the chip exists, and determines the spacing, placement, and organization of the metal pins, by which one connects to the chip.
Printed circuit boards are built to take specific chip packages at specific locations. Even if you have exactly the correct chip, as far as functionality goes, if it is in the wrong package, you can't solder it onto the printed circuit board, because the chip's pins won't fit onto the circuit board's pads or will be arranged in the wrong order, or both.
The SE/30 ROM module uses four 128K X 8 chips, but the two versions of the SE/30 ROM module of which I am aware, use either a 44 pin PLCC package, or a 32 pin SOP package.
Okay, I just checked Gamba's page <http://home.earthlink.net/~gamba2/os8_se30.html#SIMM> to refresh my memory. Apparently there are three versions of the SE/30 ROM. One uses the PLCC44 chips, one uses the SOP32 chips and Gamba lists one with PLCC32 chips as well. If anyone, has one of this latter type of ROM SIMM, conversion would be relatively simple. I have never seen one of the PLCC32 type. (John Snook, if you've got a PLCC32 SE/30 module handy, I can supply the needed chips after all.)
However, to convert one of the common PLCC44 or SOP32 types, one would need four memory chips with 128K X 8 organization and in a PLCC44 or SOP32 package. I'm not sure which of those two is more common. I would guess the SOP32 package, because it's listed in another spot on Gamba's page by itself.
So the goal would be a FLASH, EEPROM or EPROM with a 128K X 8 organization and in a PLCC44 or an SOP32 package. I do not know specfic part numbers for any such chips, unfortunately. The chips on the ROM modules themselves are Mask ROMs, so their part numbers (e.g. HN62331) are not any real help.
Anyway, if you can come up with a source of affordable SOP32 128K X 8 programmable chips, that would do the trick, and as I wrote above, I can supply the code files. I have no idea how many folks would be interested. Many of the folks who have an interest are already using a IIci or IIfx ROM.
Jeff Walther
P.S. Do you know an affordable (~$1/chip) source of WD92C32 chips? This is a Digital Data Separator in an 8 pin DIP package. I need a few because I'm trying to clone the external floppy drive for the old Outbound Model 125 (Mac clone) laptop.
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