Amiga 3000 ROM chips

[Unknown_K]

I have a friend who offered to burn some ROMs for me if I gave him the information needed.

I want to put KS3.1 ROM in my A3000 68030/25 which has 2.x in it now.

What are the proper chips/speed for this?

Looking around the forum 27C2048/27C220 seems to pop up.

ANybody done this before and remembers what to do?

[Dreamcast270mhz]

Amigamaniac's site has the chip sizes listed. AFAIK, does your 3k have the "tower"? if so, you need special speeds, there are jumpers on the mobo for this, bboah has them listed.
If it doesn't have a "tower" then there should be no issue using the same type of ROM chip as used in others, but NOT the same image as them because the 4k uses PIO 0 ide boot drivers and the 1200 too. I suggest consulting amigamaniac for the correct data to verify.

[alexh]

27C400 are the usual ones. 100ns or less. You need an A3000 specific ROM image for SCSI support. KS3.1 v40.70 or v40.68 (but there are A4000T & A4000/A1200 versions with these numbers so do not get the wrong ones or SCSI wont work)

But listen to DC270MHz, the early ROM TOWER motherboards have a different pinout.

[Jope]

If you keep the rom tower, then you can use normal rom chips. If you remove the rom tower, you need special pinout chips.

So; keep the tower!

[alexh]

I thought it is the other way around. I guess it depends what you call "special EPROMs"

The ROM tower allows you to use 27C400 EPROMs like the rest of the Amiga line. The thing is these ARE the special pinout EPROMs. The other type are the normal ones.

[Jope]

Hmm ok, let's rewind and start over. I spoke without thinking before..

Positions U180 and U181 are for HN62402/27C200/27C2100 type ROMs.

And with a little thought, I seem to remember that the ROM tower exists on the first revisions because someone mistakenly flipped the sockets on the PCB layout and they had to bodge it. I also remember there being talk of bending normal ROM legs upside down and pressing them into the sockets directly if the tower is missing and you have the old mobo. Can someone confirm this?

A quick google seems to back me up here: http://groups.google.com/group/comp....693598983e1310

U182 and U183 are the alternate positions with the 27C220 pinout, they are usually shipped with the vias filled with solder and no sockets installed. This I verified from having owned four A3000s without these sockets installed and by just looking at the schematics to double-check the EPROM model.

I think that these 27C220 ROMs are what were sold as "ROM tower kickstarts" in the past, since you could plug them into any A3000 in the "rear sockets" 182 and 183.

I still stand by what I said before: If you use U180 and U181, keep the rom tower if your motherboard shipped with one. There's nothing inherently wrong with using the tower, it makes your life simple.

[orange]

i tried 27c400 and had no luck (iirc, black screen) so decided to live with softkick.

dunno why.

edit: oh now i remember, someone told me to use 27c400 directly and take out the 'tower' grrr...

[Unknown_K]

My unit is a later 25Mhz 68030 with no ROM plug in board (real ROM not a floppy based one).

So 27C200 or 27C100 are the ones I need then?

Odd I figured you guys have gone through this many times before and still people are confused.

So which is better 40.70 or 40.68? The guy making the ROMs has 40.70 but said some machines might have issues with it so Commodore went with 40.68.

[Jope]

Both 27c200 and 27c100 chips will work, whichever you can find cheaply. Burn the images twice to the 200 chips.

Go with 40.68 to be sure.

[alexh]

27c200??

Don't you mean 27C400?

[Jope]

Nope, 32bit machines have two 256kB chips in them. Or have I lost my mind again? :-)

[alexh]

Pretty much sure that 27C200 chips are not available in significant numbers so almost everyone uses 2 * 512Kbyte ones.

I thought that is what you meant by "Burn the images twice to the 200 chips."

[Jope]

Argh, I guess there's some strange gas in the air here, and I HAVE lost my mind.

Yeah, I was off by one power of two here. I was so convinced that 27C400 chips hold two copies of a 512kB kickstart, but indeed they are $80000 bytes.

So yeah, off I go, sprinkling ashes on top of my head..

Once for C200, twice for C400 in this case, as Alex says. :-)

[Unknown_K]

Anybody have the 40.68 A3000D ROMS? If so PM me please.

[papa_november]

One set of sockets uses 27C400-type ROMs, and the other set (the rearmost one, closest to the ports on the back) uses 27C2048-type ROMs.

I think you can just toss the ROM tower if you use 27C2048-style ROMs, as it was either designed to correct problems with the 27C400-style ROM sockets or adapt 27C400-style ROMs to fit in the 27C2048-style ROM socket.

In fact, it feels more like the ROM tower was used to correct problems with the Mask ROMs than to correct problems with the board.

[alexh]

You're saying sockets U180/U181 can take 27C400 EPROMs directly on all revisions A3000 motherboards? No need for a ROM tower at all?

[Jope]

I decided to take a closer look at bboah, and the rev7 board shows that the ROM tower actually sits in the rear sockets, 182 and 183. I wish I'd have thought to double check that in the first place, would have saved me a bit of head scratching.

The rev6 motherboard shot shows 27C220 chips in the rear sockets as the schematics say. :-)

This is making more sense now when in the olden times people were selling replacement EPROMs to plug in where the tower was.. I was honestly under the belief that the tower plugged into U180 and U181.

And judging by the datasheets, 27C2048 and 27C220 are interchangeable, so no need for anyone to be confused about those two either.

Would be interesting if someone with a rom tower A3000 board would measure what signal goes where in U180 and U181.. No reason apart from my curiosity. Something is obviously wrong with the front sockets, but what. :-)

Hehe, no-one else cares, but I just have to find out. Boring trivia knowledge.

[aperez]

Jope et al,

I have a supplier who has ~100 27C2048's. They want $5/each. Are you and others interested? I may be able to negotiate a bulk buy.

[Unknown_K]

I have a guy with ROM chip coming, all I need is the code actually.

Originally Posted by alexh

I thought it is the other way around. I guess it depends what you call "special EPROMs"

The ROM tower allows you to use 27C400 EPROMs like the rest of the Amiga line. The thing is these ARE the special pinout EPROMs. The other type are the normal ones.

if i have a 3000 rev 6.3 with rom tower, can i use all 4 ports? diffrent roms in rom tower, and normal in the mobo?