Surt's Journal: TRS-80 memory

Happened to notice this post, but it was too old to reply:

  by eddy the lip (20794) Alter Relationship on Mon Aug 15, '05 03:28 PM (#13326226)

(sorry, been away from slashdot for a few days, or I would have replied sooner).

You got me on that one - I never did this myself. A friend way back in the day claimed to have jacked his TRS-80 up to 1MB. Now, this was many years ago, when people actually used the TRS-80 for other than geek nostalgia value, so I may be misremembering (or have been outright duped. I was young. It could happen....) He bragged to me about it 'cause I was stuck with the standard 32KB.

A bit of googling didn't turn up anything that would substantiate the viability of the claim. And now I have an unresolved mystery from my youth to contend with. Thanks a lot ;)

http://en.wikipedia.org/wiki/TRS-80
http://en.wikipedia.org/wiki/Zilog_Z80 (the processor in the TRS-80)

16 bit address registers + 8 bit data = 64k bytes memory max.
Hence your friend with the 1MB was lying.
Well, maybe he managed to solder on a MB chip, but the TRS-80 couldn't have used it.

"Lying" is such a harsh word

[benhocking]

Perhaps he was just talking about disk space storage. This site [trs-80.com] says that you could get a TRS-80 Model III "Business System" with 310K disk space for the low, low price of $3,972.00. Maybe if you were willing to shell out $10K you could get 1MB of disk storage somehow. (A set of disk drives?) I never had a TRS-80 (but I did have the Compucolor II [computercloset.org] with its 64K!), so I'm completely ignorant here.

Re:

[Nethead]

Maybe he used paging. I make a device back in the 80' that used the basic design (and BASIC ROM) of a VIC-20 that needed to store voice for playback on the fly. Since we weren't using the video memory space we grabbed 256 bytes of address space and brought in 256 pages of DRAM for 1MB of storage. A 68B52 then converted the bytes into a serial stream for the ADPCM chip. The only downside was we had to write our own refresh interrupt since we didn't have the video chip doing that for us.

Of course back th

1M chip

[Nethead]

"Well, maybe he managed to solder on a MB chip, but the TRS-80 couldn't have used it."

I don't think there were 1MB chips back then... at least not that one could afford. The cost point back then would be to use 64 16kx1bit DRAM chips (or 4kx4bit chips.)