BillC

The Mosaic 64K review linked in post #83 suggests putting DATA or ML subroutines in the 4K bank, and there are 4 separate banks available if needed. BASIC programs shouldn't be able to access ROM space if RAMTOP is set correctly.

Early versions of the Happy 810 firmware aren't compatible with later Warp Speed Software versions, the latest they can use is 5.3. B&C/myatari used to sell replacement ROMs that are supposed to be compatible with V7.1. I don't know if he still sells them but below is a link to a post I made a while back with the information. https://atariage.com/forums/topic/278203-what-is-this-thing/?do=findComment&comment=4017073

The ICD MIO has 256KB or 1MB RAMdisk, serial and parallel ports, and a SCSI HDD interface. There was also supposed to be an 80 column video add-on that was never delivered. The CSS Black Box has similar features minus the RAMdisk, it has serial and parallel ports, a SCSI HDD interface, plus an add-on floppy drive interface board that is able to handle up to 1.2MB 5.25"/1.44MB 3.5" drives. There were SCSI HDD interfaces by other companies, Supra/KP being one I am aware of. There is also the more recent IDE+ 2.0, which has SpartaDOS_X, real time clock, and an interface for a 2.5" IDE HDD(or flash drive with adapter).

Synfile+(probably Syncalc as well) also supports the Mosaic 64K card, which even gives an extra 4K RAM for BASIC programs with a "POKE 106,208"(increases RAMTOP to 52K).

Axlon made 32/128/256KB boards for 800, their bank selection method was later used by Magna Systems to make compatible boards up to 1MB. Mosaic made a 64KB board compatible with the 400(once some jumper wires were added to the 400 PCB), up to 3 could be used in the 800.

It's likely AXLON compatible, there was a company called Magna Systems which manufactured this type of 800 RAM board up to 1MB.

The schematics in the 600XL Field Service Manual do show L12, but many of the video components were left out of the NTSC model. Most of the video circuit is shown on page 66 of the linked PDF. http://www.atarimania.com/documents/Atari_600XL_Computer_Field_Service_Manual_Rev_1.pdf

Nezgar included a link to the Rev.2 of the 810 Field Service Manual in post #15(correction: post#18). The section on the analog board starts on page 125, and the diagnostic flowchart section starts on page 133.

I have an ASUS M5A97 from around 2011 that has a COM port header, and the M5A97 R2 released in 2013 does as well.

The following post I made in 2014 has a little more information. The jumpers simply route 2 signals to compensate for the different footprint/pinout between 2364/2764.

The damaged chips might be drawing enough power to cause the voltage drop, remove them and recheck the voltage. If it is restored to normal levels the system should be fine once ALL the damaged chips are replaced. The OS & BASIC chips may not be the only chips needing replacement.

That's for the optional controller module, which installs on the left side of the bezel.

When you put in a BASIC socket you will probably want to use a 28-pin socket, since you have the 600XL PCB version that can use a mask ROM or an EPROM for BASIC, this would allow you to install an 2764 compatible chip with Rev.C BASIC on it if desired. The soldered jumpers to select are just to the left of the capacitor behind the BASIC socket, indicated by arcs in the silkscreen similar to below. ( ( ( (

The serial# 470139 indicates 1983 production by comparing to other 800's with numbers in the same range. Given the late production date it is unlikely to have the date stamped into the case. The 2-28 would indicate Feb 28th of that year, which would be week 9 of 1983.

I was going by a Tom's Hardware review that says the WDC W65C02S6TPG-14 is pin and software compatible with the original 6502. tomshardware.com/news/mouser-6502-motorola-6800-cpu-processor,14557.html