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Atari 520STM TOS Upgrade


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I recently acquired an Atari 520STM.  It's a Rev H board.  Looking to upgrade TOS from 1.00 to 1.04.  My question is the compatibility between using 6 chips or 2 chips. Can this revision even support only using 2 chips? If not, would I still have to use 27C256 EPROMs when using 6 chips? Can I use something smaller like 27C128?

 

If I do need to use 6 chips, am I splitting it 6 ways to 32K each?

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42 minutes ago, Dasutin said:

Can I use something smaller like 27C128?

 

No, they are only 16K, each chip has to be 32K, so 27C256 is the way to go for 6 chip, I recently did it to my

520STM @ParanoidLittleMan split the ROM's for me ? worked first time.

 

I don't know if you can use the 2 chip option with your motherboard, I'm sure someone else will advise.

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You are right!  I completely did the math wrong haha. Don't know what I was thinking. I would have to use 1Mbit EPROMS for two chips and 256Kbit for 6 chips.

 

Only problem is I only have three 27C256 EPROMs. I have two C27010 EPROMs if I can go the two chip route. Any adapters to go from 32pin to 28pin?

 

If the 2 chip option is a no-go, I'll have to order more 27C256's off of Aliexpress and wait a month.

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Regardless from motherboard revision you need to go on 6 chip variant (2 is possible if there is chip 74LS11 and 3 soldering pads to set 2 or 6 chip ROM version) - because there are no 28 pin EPROMs of 1 Mbit capacity - they are 32 pin. What goes in 2 chip variant are factory (mask) programmed ROMs, and they have no pins for programming, so can be 28 pin and 1 Mbit.

Or if want to go with adapters, then can try like this:   http://atari.8bitchip.info/flashest.php

Near top are photos of 32 pin EPROMs in 28 pin sockets via 32 pin sockets . It may be problem in some STs if shield is low.

 

Splitter program:  http://atari.8bitchip.info/astopensw.php

at about 60% of page.

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Thanks for explanation.  I was able to pick up some 27C256's off of Amazon and arrived yesterday. I used the Hatari emulator to run the romsplit app on the TOS 1.04 image. I brought the hi-lo split ROMs back over to Windows to burn on the EPROMs. When I place them in the correct order on the Atari 520ST, fire it up, it doesn't boot.

 

Inspecting the split files finds all Hi and Lo files are different but are identical. The Hi files are all the even bytes, but only up to the first 512 bytes, then zero for 512 bytes, then the same 512 bytes even bytes as before, then 512k of zero bytes, and so on. 

The Lo files are all of the odd bytes and repeat in the same order as the Hi.

 

Besides the incorrect files, is it fair to say the Hi files are all of the even bytes, and the Lo files the odd bytes? If so, I can just do that myself. 

 

 

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@TGB1718 Thanks for posting the example files. That confirms my assumptions. Too bad it's the 50hz UK 1.04 ROM. I'm from the States :)

 

No worries! I was able to split the ROM by even/odd bytes, then split each file by 32KB. I'm going to burn them to the EPROMs and test. 

 

Thanks for your help!

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@tjlazer Thanks for the offer, but I'm all set.  I was able to burn the set and test.  It boots in TOS 1.04!

 

I got a couple of those 4MB RAM expansion PCB boards made https://github.com/agranlund/STRam. They should be here early next week.  I might sell the remaining boards if one works in mine.

 

It would be neat if I could put TOS 2.06 on this 520STM, but it doesn't seem possible if it doesn't have the 74LS11 chip. 

 

 

 

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11 hours ago, Dasutin said:

Thanks for explanation.  I was able to pick up some 27C256's off of Amazon and arrived yesterday. I used the Hatari emulator to run the romsplit app on the TOS 1.04 image. I brought the hi-lo split ROMs back over to Windows to burn on the EPROMs. When I place them in the correct order on the Atari 520ST, fire it up, it doesn't boot.

 

Inspecting the split files finds all Hi and Lo files are different but are identical. The Hi files are all the even bytes, but only up to the first 512 bytes, then zero for 512 bytes, then the same 512 bytes even bytes as before, then 512k of zero bytes, and so on. 

The Lo files are all of the odd bytes and repeat in the same order as the Hi.

 

Besides the incorrect files, is it fair to say the Hi files are all of the even bytes, and the Lo files the odd bytes? If so, I can just do that myself. 

 

 

ROMsplit program works reliable, and lot of people used it.  What may be problem with Hatari is when TOS image file name is not in 8.3 format, but longer, with lower case letters ...  I noticed then some strange errors. So, best to rename it to something like TOS104US.IMG   .  And split in 6 parts, of course. 

Btw. I use Steem for splitting (v3.2 , original) .

Edited by ParanoidLittleMan
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1 hour ago, Dasutin said:

@tjlazer Thanks for the offer, but I'm all set.  I was able to burn the set and test.  It boots in TOS 1.04!

 

I got a couple of those 4MB RAM expansion PCB boards made https://github.com/agranlund/STRam. They should be here early next week.  I might sell the remaining boards if one works in mine.

 

It would be neat if I could put TOS 2.06 on this 520STM, but it doesn't seem possible if it doesn't have the 74LS11 chip. 

 

 

 

CAS1L and CAS1H is also flipped according to this thread.

 

I made an update on that PCB, you can find it at the end of the thread above. But I uploaded it here as well. No need for bodge wire. Read README2.TXT for full info.

STRam4mb.rar

Edited by snarkdluG
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8 hours ago, Dasutin said:

@tjlazer Thanks for the offer, but I'm all set.  I was able to burn the set and test.  It boots in TOS 1.04!

 

I got a couple of those 4MB RAM expansion PCB boards made https://github.com/agranlund/STRam. They should be here early next week.  I might sell the remaining boards if one works in mine.

 

It would be neat if I could put TOS 2.06 on this 520STM, but it doesn't seem possible if it doesn't have the 74LS11 chip. 

 

 

 

The UK set puts your ST in PAL mode, if you need it to be NTSC, use the USA version.

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To make TOS 2.06 in some ST 74LS11 is not enough.  The reason is different address space of 2.06 than TOS 1.00-1.04 . Instead range $FC000-$FEFFFF (192KB) 2.06 is $E00000-$E3FFFF (256KB). So, even if would change 2.06 start address it can not fit in area, because at $FF0000 HW register area starts.

Solution is adding HW address logic:  http://atari.8bitchip.info/tosimav.html

At 65% of page is paragraph:  Solution for TOS 2.14 or original 2.06 with 4x 28 pin EPROM chips - no need for intermediate socket, so will remain low.

 

Considering UK TOS instead US one - beside PAL mode there is little difference in keyboard layout handling.  Setting NTSC mode, better said refresh rate to 60 Hz is simple, there are very short programs for that.

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