Basic rev'C' on Eprom

[Roydea6]

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

[+bob1200xl]

For 8K of data, you need 13 address pins, 8 data pins, two power pins and two control pins. That's at least 25 pins - not going to find an 8K EPROM with 24 pins... Oddly, the 600XL has a provision for a 28 pin EPROM for BASIC - the 800XL does not.

 

 

Bob

 

 

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

[Fuji-Man]

Well, chalk another one up for the 600XL on the plus side... LOL.

 

Anyway, I've performed one of the home brew 64k upgrades on my 600XL. Now when I need to reboot the machine, the machine retention is like 10 seconds off before I can get a proper clean reboot. Any sooner and the machine comes up in a 'locked' state. Any ideas?

 

If I had a schematic and an idea where to look for problems, I'd be working on it now. I'll fire up the O'scope and see if anyone has ideas while its warming up..

 

Fuji-Man

 

For 8K of data, you need 13 address pins, 8 data pins, two power pins and two control pins. That's at least 25 pins - not going to find an 8K EPROM with 24 pins... Oddly, the 600XL has a provision for a 28 pin EPROM for BASIC - the 800XL does not.

 

 

Bob

 

 

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

[mimo]

For 8K of data, you need 13 address pins, 8 data pins, two power pins and two control pins. That's at least 25 pins - not going to find an 8K EPROM with 24 pins... Oddly, the 600XL has a provision for a 28 pin EPROM for BASIC - the 800XL does not.

 

 

Bob

 

 

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

How?

Any chance you could let me know the details

 

Thanks

[+bob1200xl]

Some dynamic memory will hold its data for an incredible length of time. I did a mod long ago that forces a 'hard' reset (allowing you to re-boot unconditionally and save the contents of ramdisk) I called it 'The Freezer" if you want to search for it. Pretty simple - add an XOR gate in the T3 line that the cartridge asserts and use a PB switch to invert the line. This will produce a power-on reset. You can also just insert (or remove) the cart and do the same thing... hard on the cart and contacts, though.

 

 

Well, chalk another one up for the 600XL on the plus side... LOL.

 

Anyway, I've performed one of the home brew 64k upgrades on my 600XL. Now when I need to reboot the machine, the machine retention is like 10 seconds off before I can get a proper clean reboot. Any sooner and the machine comes up in a 'locked' state. Any ideas?

 

If I had a schematic and an idea where to look for problems, I'd be working on it now. I'll fire up the O'scope and see if anyone has ideas while its warming up..

 

Fuji-Man

[+bob1200xl]

How,,, what?

 

Bob

 

 

 

For 8K of data, you need 13 address pins, 8 data pins, two power pins and two control pins. That's at least 25 pins - not going to find an 8K EPROM with 24 pins... Oddly, the 600XL has a provision for a 28 pin EPROM for BASIC - the 800XL does not.

 

 

Bob

 

 

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

How?

Any chance you could let me know the details

 

Thanks

[puppetmark]

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

 

I am not sure of what you are ultimately trying to accomplish but I can tell you that you can put BASIC rev C in a 27C64 EPROM. However, the pinout for the BASIC ROM on the 800XL motherboard is not pin compatible with a 27C64 EPROM but all the necessary lines are there. If you make some kind of adapter board or point to point wiring it will work.

[mimo]

Sorry, not a very good reply.

Could you let me know how I could add Basic Rev C to a 600XL using an EPROM

 

Thanks

[puppetmark]

Sorry, not a very good reply.

Could you let me know how I could add Basic Rev C to a 600XL using an EPROM

 

Thanks

 

If you don't want to make an adapter (as I mentioned in my earlier post) , you can put BASIC REV C on a MCM68764 and it will be a drop in replacement for the Atari Basic ROM. It should work in all XL or XE except the XEGS. The MCM68764 is VERY hard to find and not nearly as cheap as the 27CXXX family. Looks like arcade components has them:

http://www.arcadecomponents.com/catalog/it...646/6155711.htm

 

Not all EPROM burners that can burn MCM68764 EPROMs either, some burners require an adapter board, so that could be a problem too.

 

check out this link for some info and a 27c64 adapter. the 2364 discussed on the following site is a one time programmable part or, in the ATARI XL, would be the original BASIC ROM

 

http://www.faime.demon.co.uk/retro/2364.html

Edited September 2, 2008 by puppetmark

[classics]

Just double the image and put it on the 27128. Stack that on top of the OS rom, connect the CE/OE pins from the new ROM to the CE/OE pin on the basic socket instead of the one on the eprom below.

 

Steve

[+bob1200xl]

Just looking at the schematic, there are a couple of jumpers on the motherboard that need to be set right. Replace the 24 pin socket with a 28 pin... should be OK.

 

This is not an endorsement, however. It looks like it's designed to do that. Doesn't mean it works that simply. You need to find someone who has actually done this. I have not.

 

Bob

 

 

 

Sorry, not a very good reply.

Could you let me know how I could add Basic Rev C to a 600XL using an EPROM

 

Thanks

[+Larry]

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

 

This has come up here several times, so you might search under "2364" or "basic rom adapter" or such.

 

The C64 folks have had similar issues and there has been more than one 2364 adapter pcb made. Here is one such (which I have not tried):

 

http://freenet-homepage.de/x1541/hardware/2364.html

 

Pretty sure there was a pcb run made in the US a year or two ago. You'll need to search the C64 stuff to find it. I'm also pretty sure there was a thread about this on the "Lemon64" web site.

 

Presume you are aware that both B&C and BEST still sell the actual "C" roms for $12-15. Less overall hassle, perhaps.

 

-Larry

[re-atari]

Hi,

I was wondering if I could put atari basic rev 'C' on a 27c128 get it installed on my 800xl. I have several OSroms on a 27c512 eprom and was wondering if the same could be done for rev 'c' I know the pinouts are different 24 pin for basic and 28 pin for the OSrom. I tried puting rev 'C' on a 24 pin 2732 eprom but it didn't fit. I have not been able to find any larger 24pin eproms.

 

You can read how to put a standard 2764 into the XL's socket in this topic. I uploaded a simple wiring schematic in post #6.

 

If you don't have a 2764 at hand, you can quite easily substitute it with a 27128. If you don't rewire A13, you just need to put the contents of the Basic Rom in the 27128's lower 8K addres space.

Alternatively, you can divide its 16K address space in 2 separate 8K blocks. You do this by connecting A13 through a 3k3 or 4k7 resistor (either will do) to +5V, and wiring it to GND through a flip switch. A 27128 has A13 on pin 26, on a 2764 this pin is NC. With the switch open, A13 is connected to +5V which activates the lower 8K. When closed A13 is connected to GND, which blends in the upper 8K. BTW: your XL will thank you for turning it off before flipping this switch. This way you could put rev. B and rev. C in a single eprom and switch between them if needed (not that you'd ever want to step back to rev. B).

I did something similar with the XL's OS, by using a 28F020, 4 resistors and a BCD encoded switch built on a piece of veroboard. Before anyone asks: no, I do not reprogram the flashrom using the XL. That's when I reach for my All-07 or my GALEP III.

 

re-atari

[+Larry]

Just double the image and put it on the 27128. Stack that on top of the OS rom, connect the CE/OE pins from the new ROM to the CE/OE pin on the basic socket instead of the one on the eprom below.

 

Steve

 

Hi Steve-

 

How clever!

 

Just to be sure -- the 2364 doesn't have a separate OE pin, does it? So *both* lines connected to the CE pin on the Basic socket?

 

Presume this would also work with a 2764? Bend up A13 on a 2764 (pin 26)?

 

-Larry

[classics]

Just double the image and put it on the 27128. Stack that on top of the OS rom, connect the CE/OE pins from the new ROM to the CE/OE pin on the basic socket instead of the one on the eprom below.

 

Steve

 

Hi Steve-

 

How clever!

 

Just to be sure -- the 2364 doesn't have a separate OE pin, does it? So *both* lines connected to the CE pin on the Basic socket?

 

Presume this would also work with a 2764? Bend up A13 on a 2764 (pin 26)?

 

-Larry

 

Correct, tie CS and OE together, then to the OE signal for the BASIC rom, either on the socket or the MMU.

 

If you use a 2764 the NC pin should be left unconnected. Some don't have this connected to anything but some will malfunction if you connect it to a signal, so its better to just bend it up or break it off.

 

Steve