What are "standard 4164" memory chips?

[ceratophyllum]

I recently got another almost-working coco2 and I think it has 16K ram.

The RAM might be bad, because PRINT MEM gives a funny, small number:

6913.

 

Everything on this coco2 is socketed so it should be an easy upgrade, if what I read here is correct.

 

I just solder across a jumper and put in 8 4164s.

 

But what is 4164? Is this the same part?

[JamesD]

Extended Color BASIC takes up some of the RAM.

It reserves memory for the standard text screen, graphics memory, some file space,string space, etc...

I thought there was still at least 10K available on a 16K system though.

Type PCLEAR 1 and PRINT MEM again and see if you have the same amount of RAM.

[ceratophyllum]

I wrote down the wrong number above, it should be 6439.

PCLEAR 1
PRINT MEM

gives 11047

 

I'm also autoloading HDB-DOS 1.4 DW3 from a cartridge.

 

So this is a 16KB system?

Edited April 18, 2016 by ceratophyllum

[JamesD]

I wrote down the wrong number above, it should be 6439.

PCLEAR 1
PRINT MEM

gives 11047

 

I'm also autoloading HDB-DOS 1.4 DW3 from a cartridge.

 

So this is a 16KB system?

I was thinking the number should be close to 12K for a 16K system so that sounds normal. .

 

[ceratophyllum]

I tried a LOADMing a few games(Space Ambush, Cuthbert in Space) over drivewire and it looks like they work ok.

 

Now if I could just fix the damn keyboard...Took all those tiny screws out, dusted it off a bit, and voila the G key still doesn't work. That plastic membrane sandwich looks like a really great home for mold and tiny bugs. Maybe I'll get a PS/2 adapter from cloud9....

[Rolo]

PCLEAR 1

PRINT MEM

gives 11047

 

I do not agree.

I set up a few CoCo 16k-machines in XROAR.

They all are giving me higher free RAM numbers, varying on which BASIC and EXTENDED BASIC roms I'm using. I know, it's only an emulator, but most of the time, it's right!

I'd guess you have kind of a RAM problem, too. Did you already replace the 4116 (is this what has been in?) with 4164?

[ceratophyllum]

The games seemed fine at first but little things were off like some letters were corrupted so I went ahead and soldered that jumper W1 (Figure 1 in the PDF below) and replaced them with NEC 4164 chips from eBay and now it is fully working except for the G key.

 

The old chips have numbers:

 

8040517

8329

 

and Motorola "M" and Tandy Computers "TC" symbols.

 

 

Coco2 memory upgrade instructions

 

 

The May 1984 Rainbow (page 49) referenced above is also a very nice help for the confusing and hazardous (There are too many types of coco1 boards!) coco1 RAM upgrade. I just ordered some more 4614 RAM to upgrade my 16KB 26-3004A "NC Board" coco1.

Edited April 23, 2016 by ceratophyllum

[Rolo]

All right, this means you are getting a reasonable byte count for PRINT MEM? Just wanted to make sure, that you don't still have those partly bad chips inside. I also upgraded my D32 to 64k.

[ceratophyllum]

With the 8 new 4164 chips, I get 24871. I have an Extended Color BASIC ROM in this system, no cartridges or other funny stuff inserted. According to the the instructions above, this is the right amount:

 

Too bad the author doesn't say which issue and page of RAINBOW has the memory test program. I'll just play some games and see what happens.

[Rolo]

24871 is fine. XROAR reports the same for ExtColBas1.0 and 1.1

"Quick Diagnostic Rom" (Dragon cartridge) could help. Or the other one "DIAGS21". Since they run from cartridge, they can test "all" memory locations. The programs visualize memory on screen. As far as I understand, in case of error, some artifact should be visible.