800 ROM board differences

[adam1977]

I need a new ROM board for my 800, but getting a PAL one is proving to be impossible, but NTSC one's are available; can anyone tell me if I could use an NTSC one instead of a PAL board please?

[xrbrevin]

I have an NTSC 800 and it works fine via the monitor port into s-video on my UK flat panel screen. The image is a little larger than the PAL machines, it fills the screen more. The games run a little faster but i believe this is due to the different crystal oscillator on the PAL and NTSC PCBs - used for the the different hertz between the 2 types.

what is wrong with the ROM board you have? can it be repaired?

[adam1977]

Hi,

 

When it's plugged into the computer it gives all sorts of problems, see my post here i'm not sure if it can be fixed, I haven't got any spare chips to swap over and try

 

If an NTSC ROM board would work then i'll see if I can get one

[Rybags]

You'll get slower key repeat rate and the cassette bitrate tables will be wrong but supposedly the sytem will cope with that.

 

If you were to replace with Eproms of the PAL OS you only need to do the 2 x 4K ones, the 2K FP is the same.

[xrbrevin]

if you still have the second 800 computer, swap the chips from the working ROM board into the non-working one and if it works, you know the PCB is not at fault

[+Nezgar]

If the 2x4KB ROM's are faulty, or you just want to put a PAL OS on an otherwise NTSC personality board, two 2732 EPROMs are a drop-in replacement. (Programmed with two 4KB parts of your choice of 800 OS). Math pack is the same.

 

i.e. the 10KB ROM's here would need the first 2KB (math pack) stripped off ($0000-$07FF), and the next 2 4KB segments saved out to 2 separate files $0800-17FF, and $1800-27FF for the two 2732 chips.

http://ftp.pigwa.net/stuff/collections/atari_forever/ROM/Rom%20-%20OS/800ROMS/

[adam1977]

Thanks for the replies, but i've placed an order with Best Electronics for a new PAL one, there was a cheaper option on shipping so it's worked out quite well

[Jeffrey Worley]

I have an 800 with a bad Antic and a bad rom #a402.  Can anyone tell me what eprom type to use for what rom.  There are three so I figure I should go ahead and get info on all three.  I gather two are 4k (2732?) and one is a 2k (2716)?  Can anyone validate this for me?

 

Thanks,

RSVP

YHOSvt.

** TNM **

[+Nezgar]

@Technoid Mutant I believe you are correct. Left to right on the CO12989 OS/personality board, card edge down the chips are:

 

CO14599B NTSC-B OS, HI, 0xF000, A401 - 2732 style pinout, 350 ns max access time
CO12499B NTSC-B OS, LO, 0xE000, A403 - 2732 style pinout, 350 ns max access time
CO12399B 2KB Math Pack, 0xD800, A402 - 2K 2716 style pinout, 350 ns max access time.

 

If a 2716 for the math pack is hard to obtain or program, a 2732 with the 2KB repeated should work. If you don't have the means to program them yourself, PM me - I have 2732's on hand and can drop them in the mail to you for my cost.

[BillC]

I'm not certain this is the case with the 800 OS ROMs, but believe most ROMs 8KB and under are 25XX compatible.

I know the 1050 uses jumpers to select between ROM or 2732 EPROM for the firmware, and also that some 600XL PCBs use jumpers to select between ROM or 2764 EPROM for the BASIC chip.

[+Nezgar]

Hmm. Yeah true, it would make sense for them to be 2332/2316 types like 4K/8K carts. If so, all pins on both of the 2 OS ROM's would possibly be wired straight across, with the chip enable's inverted opposite in the chips themselves. Maybe I was confusing people using the Onmimon boards with EPROMs.

 

In that case, the 23xx adapter from retro innovations could work: adapt a 2764 to 2316, 2332 or 2364 configuration with configurable chip select options: http://www.go4retro.com/products/23xx-adapter/

 

Got a few of these PCBs but havent assembled them yet, to try in 810/1050/400.

[Jeffrey Worley]

This link was an inspiration: https://pinside.com/pinball/forum/topic/28c16-eeprom-replacement-for-2716-eprom

 

Standup video arcade propellerheads talking about the equivalence of the AM28c16 to the 2716.  They are apparently pin-compatible.  Now I know some folks will mention the data retention of EEPROM vs EPROM, and I'm not so sure that is very relevant.  The makers of EEprom guarantee 10 years to 20 years of retention.  That's not bad at all and the chips are a lot easier to get and to program than the original 2716.  The 28c32 is, unfortunately, unobtainable, but I gather that one can adapt a 28c64 to do the job.

 

What I'm thinking to do is make my own US Doubler.  I have a burner on the way and some eeproms as well.  I don't have a compatible rom pack for the 1050 and don't have an eprom eraser, so even if I bought some 2732's I'd not be able to clear them before programming.  Anyway...

 

Another project I'm SERIOUSLY considering is this Axlon 512k board.  This looks very doable and neat.  I like it so much I ordered another SIDE2 cart to pair it with when I get the 512k board installed.  Has anyone done this board?

 

In the .zip for the 512k project there are two sets of files for two versions of the board, a B version and and F version.  Does this refer to the revisions of the ram boards with which the 512 board will co-reside in the final build?  Mine are all F's I believe, but it's important for me to know which version to have made.

 

Second, is anyone ELSE interested in doing this project or having one built?  If I'm going to have one board made, I might as well put it out there and make more than one.  Let me know if you are interested and you can re-emburse me for for the hardware and shipping.  I'm not interested in making a buncha money on something like this.  It looks fun to build and I'd like to build several.  If I can get some free parts out of the deal that would be GREAT!.

 

Hit me back.

 

RSVP

YHOSvt.

** TNM **

 

[+Nezgar]

18 hours ago, Technoid Mutant said:

Standup video arcade propellerheads talking about the equivalence of the AM28c16 to the 2716.  They are apparently pin-compatible.  Now I know some folks will mention the data retention of EEPROM vs EPROM, and I'm not so sure that is very relevant.  The makers of EEprom guarantee 10 years to 20 years of retention.  That's not bad at all and the chips are a lot easier to get and to program than the original 2716.  The 28c32 is, unfortunately, unobtainable, but I gather that one can adapt a 28c64 to do the job.

Yes they probably are pin compatible. But I think not compatible with the 800 math pack ROM without modification, as it is probably expecting 2316 style. I had some adventures trying to make ancient 2532 EPROM's work in a 1050 under the premise that they were 'pin compatible' with the 2332 mask ROM. Take a look at this thread: https://atariage.com/forums/topic/286590-repair-of-two-1050-floppy-disk-drives/?tab=comments#comment-4214749

 

In reality it turned out that the 2532 used Pin 20 for A12 or "Output Enable" (High=Power Down), whereas Atari's 2332 used Pin 21 for A12, and used active HIGH, so pins 20/21 had to be tied and supplied an inverted signal. In the 1050 this signal could be pulled from an existing inverted output, so there may be a similar source on the 800 CPU board. I expect some similar trials if you attempt to use a 2716 in place of a 2316. Hence my aforementioned adapter that does all this for you.

 

Last thing is to not use EPROM/EEPROM's faster than 200ns, and slower than 350ns for OS ROM's. I've had some interesting results with a 150ns OS EEPROM in an XL, ie Random screen text corruption. A lot of EEPROMS are 150ns or faster. Might be OK in a game cartridge or BASIC, but as an OS rom it's much more picky. I expect this would be a concern for the 800 as well.

 

18 hours ago, Technoid Mutant said:

What I'm thinking to do is make my own US Doubler.  I have a burner on the way and some eeproms as well.  I don't have a compatible rom pack for the 1050 and don't have an eprom eraser, so even if I bought some 2732's I'd not be able to clear them before programming.

I think all of the 2732's I've purchased from eBay/China were already blank. In fact, all UV EPROM's I've bought (last few years) were always blank... its only a set of 28C64 EEPROM's that had some content, but those are super-duper quick to erase anyway So, I think you'd have a good chance you'd be OK without an eraser immediately. Otherwise, I've been using an el-cheapo ebay unit with no problems: https://www.ebay.com/itm/132128369061

 

The 6810's for a homebrew US doubler can sometimes be the harder to find, at least for cheap. Check this post of mine on a previous topic showing an 'optimized' way to construct the dual-stacked 6810 RAM chips:

https://atariage.com/forums/topic/220482-1050-us-doubler-speed/page/5/?tab=comments#comment-4011333

 

Also, if your 1050 happens to be the less common made in hong kong / WST mech variant, there is a recent patch of the official ICD ROM that incorporates the faster stepper timing found in the stock ROM of those drives: https://atariage.com/forums/topic/156462-1050-roms/?do=findComment&comment=4061547

 

 

[Jeffrey Worley]

It looks like out of my ten 28c16's I got one good one.  You are right about it freaking the 800 out.  The chip programs and verifies and the Atari boots, but it freaks Pokey out something fierce.  Keyboard is wild, and sio is broken.

 

The strange thing is that while trying this out and verifying that my rom was bad (the original), I tried the cart with no math rom installed at all.   The machine works fine until you call on the mathpack, which is surprisingly infrequent.  It took me a while to find something that wouldn't run, finally I put BasicXL on my cart and loaded that, thinking I'd do a ?sin(x) and test the floating point that way.  BXL will bomb at the Ready prompt and not accept any input without the chip installed, so there's a test for you.  If you install a good chip it works just fine and of course returns valid output for Sin(X).

 

I just got my burner today.  Woot!

 

** TNM **

 

[Urchlay]

BXL will bomb at the Ready prompt and not accept any input without the chip installed

Plain BASIC will fail too.

returns valid output for Sin(X)

Fun trivia: the code for SIN() actually lives inside the BASIC (or BXL)
cart. Though it does call several of the OS FP routines, so it's still
a good test.

[Kyle22]

These look good for Doublers.

 

[Jeffrey Worley]

An update on the 512k ram boards for the Atari 800.  I just got the 74F138 chips in today, got the capacitors the other day.  All but the 138's and the ram chips are installed on the boards already.  When the rams come in, which might be tomorrow but very likely Monday, they are in Orlando now, I will stick them in the boards and start testing.  Cross your fingers everyone.  I really want this to work the first try. ?