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Old 06 December 2009, 10:47   #1
RedskullDC
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Homebrew EPROM Kickstart board (pron for zetro et al.)

Hi All,

Few piccies of a quick weekend hack.

Kickstart replacement board using a 27C322 EPROM, which will hold 8 seprate 512K kickstart images.

Purely a kickstart replacement for 16bit data bus Amigas. Doesn't do any fancy 1MB remaps, though wouldn't be too hard to add that functionality.

As you can see, wiring is minimal, so I made it up on a scrap piece of experimenter board.
Three high address bits (A18, A19, A20) are either 5V or pulled low through 4.7K resistors depending on the DIP switches.
A17 is also switched allowing the board to be used on Amigas with A17 on either Pin 1 or Pin17 of the Kickstart socket.

Would be easy to make a 32bit version to suit A1200/A4000.

Source of parts.
27C322 eprom:
http://cgi.ebay.com.au/ws/eBayISAPI....m=220455183552
(US$4.90 for 2)

48Pin ZIF socket:http://cgi.ebay.com.au/ws/eBayISAPI....m=330379543863
(US 0.99c each!!)
(optional, ordinary dip socket will do but ZIF is so much easier when experimenting.)

Total cost around $5 if you factor in shipping etc.

----
miscellaneous:

Datasheet for M27C322:
http://www.alldatasheet.com/datashee...322-100B1.html

Programmer to suit 27C322:
top2048/top2049 etc.

Eprom eraser:
http://cgi.ebay.com.au/ws/eBayISAPI....m=320458784692
(AU$15)
Yes, Cheap toothbrush sanitizers WILL erase EPROMS. Lamp runs on the same frequency as those oh-so-expensive commercial eprom erasers.
Unit switches off automatically after 10mins, most EPROMS normally need about 15mins to erase completely. Just open the lid, and run it again.

Cheers,
Red
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Old 06 December 2009, 11:18   #2
alexh
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Nice.

Slightly off-topic, I've been thinking about making custom 512Kbyte KS3.9 EPROMs for my two A4000's for a while now to avoid reboots. Is it particularly hard?

I would have liked to tried bigger (1MB+) kickstart ROMs and add extra romable modules but I'm sure you know the A4000 (unlike A1200 & A600) can only access 512Kbytes of ROM
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Old 06 December 2009, 12:49   #3
RedskullDC
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Hi Alexh,
Quote:
Originally Posted by alexh View Post
Nice.

Slightly off-topic, I've been thinking about making custom 512Kbyte KS3.9 EPROMs for my two A4000's for a while now to avoid reboots. Is it particularly hard?

I would have liked to tried bigger (1MB+) kickstart ROMs and add extra romable modules but I'm sure you know the A4000 (unlike A1200 & A600) can only access 512Kbytes of ROM
Easy as pie to make the 1MB images, courtesy of Doobrey's Remus software:
http://www.doobreynet.co.uk/beta/index.html
He's on EAB if you want to ask him any questions.

I didn't know that the 4000 didn't support 1MB ROMS

What do you see when you fire up a monitor program and examine the $E00000-$E7FFFF area?

Is always possible to fool the GARY chip as far as addressing goes...
http://aminet.net/docs/hard/Ramrom.lha
One of my old projects from 1990 (cringe) which shows how to overlay ROMS in an A500 with RAM by fooling GARY.

Will be different on 4000, but the principle is the same.

Cheers,
Red

Last edited by RedskullDC; 06 December 2009 at 13:10.
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Old 06 December 2009, 19:27   #4
cosmicfrog
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hasn't it been recently discovered that 1200/600 do 2meg roms as well
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Old 10 December 2009, 00:03   #5
rkauer
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Now I need someone to burn me a 1.3+ latest SCSI.device and 2.05 on the same chip to use on my A500...

Anyone up to the task? I don't have an EPROM programmer. I can supply proof that I own the real ROMs.
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Old 10 December 2009, 00:12   #6
alexh
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A500 & scsi.device??

You got a CFIDECP?
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Old 10 December 2009, 02:41   #7
rkauer
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To boot under 1.3 with the IDE68k device.
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Old 10 December 2009, 10:50   #8
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I thought so. (CFIDECP is the new name for IDE68k)

I guess you'd have to do the leg-work and prepare the KS1.3 image.
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Old 15 December 2009, 01:49   #9
Doobrey
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Quote:
Originally Posted by RedskullDC View Post

I didn't know that the 4000 didn't support 1MB ROMS

What do you see when you fire up a monitor program and examine the $E00000-$E7FFFF area?
From a vague memory of testing it out 18 months ago or something...
First off, the 68040/060 library sets the MMU to redirect reads to $E00000-$E7FFFF.
That was easy enough to bypass by loading a dummy cdstrap resident before Setpatch. (040/060 libs check for this, thinks it's running on a CD32 and doesn't redirect read accesses)

After that, trying to read on an A4000 just gave me bus exceptions..
IIRC, I flipped a bit in Fat Gary (or was it Ramsey?) to enable bus timeouts, but I never got a ROM mirror on reading, just random junk on the data bus.

Quote:
Is always possible to fool the GARY chip as far as addressing goes...
http://aminet.net/docs/hard/Ramrom.lha
One of my old projects from 1990 (cringe) which shows how to overlay ROMS in an A500 with RAM by fooling GARY.

Will be different on 4000, but the principle is the same.
Yeah, C= had the same idea on the A4000T.
There's a missing PLD and jumpers to enable a 'BigROM' patch.
Basically, the PLD feeds Fat Gary an address in the $F80000-FFFFFF range whenever the real address is $E00000-E7FFFF to make it generate the /ROMEN.

IIRC, there's also the minor problem of not enough address lines on the ROM sockets to use larger ROMs

TBH, with the Deneb/KickflashOS4 cards, there's not really much point in hacking A4000/A3000's to take larger ROMs.
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Old 09 January 2010, 18:24   #10
sanjyuubi
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I made something like redskullDC but using 27c160 for A600 and A1200 some time ago, 27c322 are not available in my country. 16bit version can hold up to 4 kickstarts and 32bit version up to 8 (512k).
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