Freddy 800XL?

[+Larry]

Showing my ignorance here... what exactly is a "Freddy 800XL?" I keep reading references to "Freddy" but I don't believe I've ever met him...

 

I remember that when the 130XE came out (U.S.), "Freddy" was described as the MMU. But I also seem to remember that was later said to be incorrect -- that Freddy was not the MMU. If not the MMU, what does Freddy do for a living in the A8? Did late model (Taiwan) NTSC 800XL's have typically have Freddy on them -- or just PAL versions? I have a bunch of late model Taiwan NTSC boards, so is there a specific part number that I can check for on the board?

 

Thanks,

Larry

[flashjazzcat]

Was wondering myself, so just found this:

 

FREDDIE

CO61922, CO61991

 

The 65XE/130XE/800XE/XEGS contain a small additional LSI called FREDDIE, a RAM address multiplexer. According to James Bradford, "FREDDIE is a type of memory controller. It takes the address and clock from the CPU and multiplexes it with the appropriate timings and signals to use DYNAMIC memory. FREDDIE also buffers the system clock crystal and divides it down then feeds that to GTIA. The XEGS has a FREDDIE but it doesn't have the extended RAM. Even if it did, you would still need the chip that does the REAL bank switching. It is a small 16-pin chip (Atari/Best Electronics catalog number CO25953: rev9/page 42). It gets RAS from FREDDIE, the bank select bits from PIA, A14, A15 and the 6502 halt signal to control which bank of 8 chips RAS goes to. A14 and A15 then go to FREDDIE for the address range of the extra memory bank (or normal address range with no bank switching). The ANTIC/6502 select bits in combination with the 6502 halt line, control the switching of the PIA bank number bits to A14/A15 and which bank of memory RAS goes to. Why people say FREDDIE does the bank switching is beyond me. An 800XL can look like a 130XE with that 16-pin chip installed (That's right NO FREDDIE) and an extra 8 RAM chips."

 

And more recently James Bradford has written: FREDDIE is just a memory decoder and timer. It replaces several chips in the 800XL. The small chip near FREDDIE does all the bank selection. CO25953. One line from FREDDIE, Ras (or is it cas?) goes to this chip, Halt and the bank /processor select lines go into this same chip and ras (cas?) comes out. A pin for each bank. If I remember correctly, refresh also goes into this small chip. It would be quite easy to make an 800XL work just like a 130XE with this chip since Ras (Cas?) is required by ALL dynamic RAM.

 

Read more: http://www.faqs.org/faqs/atari-8-bit/faq/section-12.html#ixzz0U0kmAloC

[+Larry]

Thanks, Flashjazzcoat. I've done some more searches, but can't find any info on if Freddie is used on the late model Taiwan 800XL boards. I suspect it is not, but I'm going to look at a couple of my newest boards.

 

Was wondering myself, so just found this:

 

FREDDIE

CO61922, CO61991

(snip...)

 

[+hunmanik]

Thanks, Flashjazzcoat. I've done some more searches, but can't find any info on if Freddie is used on the late model Taiwan 800XL boards. I suspect it is not, but I'm going to look at a couple of my newest boards.

 

From what I've pieced together to date, I believe that all of the Tawain 800XL units produced by Atari Corp. in fall 1984 include Freddie. These include PAL "800XLF" boards and SECAM "ROSE" boards. But, I don't believe there are any NTSC 800XL boards with Freddie.

Edited October 19, 2009 by hunmanik