memory, but not sure what kind of

They look more like ROM sockets to me, maybe BASIC ROM's? Is the 1000TL a 8088/8086 system?

this may be the optional 128kb for onboard graphics
@BSA ROMs installed in pairs? thats new to me; where could i read up on that?
ps its a 286

i wonder if it's for the on-board rom DOS. Perhaps they intended for it to have more space or upgrades.

mrau wrote:

this may be the optional 128kb for onboard graphics
@BSA ROMs installed in pairs? thats new to me; where could i read up on that?
ps its a 286

A lot of old video cards have the ROM's laid out that way, Paradise, OAK etc. that's what made me think of it. Not familiar with 286 system's tho so will leave it to the experts.

the video ram upgrade is actually much smaller chips, the same as the main system memory.

I just found that the bios on the 1000TL was upgradeable, so I feel pretty confident that this must be the ROMs themselves, along with potential additional expansion space.

I wonder if it'd be possible to flash my own ROM dos version and replace these...

http://www.oldskool.org/guides/tvdog/1kfaq.html#II.K.5

seems youre right

So this piques my interest.

Should it be theoretically possible to dump the contents of these ROM chips, flash a replacement, and swap them back in?

It could be super interesting to fill out all four banks and end up with DOS 5.0/6.22/whatever instant booting system.

The sockets gave Tandy cost options. It allows the to use whatever was cheaper at the time of construction of the machine. Older ROM's that had less available space for DOS and Deskmate, but require more of them. Or larger ROM's that were newer and cost more per chip, but require fewer chips. There will be a limit on maximum addressable ROM size so you can't just fill in the empty sockets with the same size as the ROM's in the other sockets. Most of the Atari 16bit line of computers did the same thing.

You should be able (never tried this so your on your own here) be able to put your own ROM's with a newer DOS and no DeskMate. Just keep to the same ROM size that currently installed.

Oh I see. Still, that gives me an interesting little side project when time allows.

The TL has a pair of 256KB ROM chips. giving 512KB of ROM. However, the memory map of the PC compatible does not have enough space for so large a ROM, so it is paged in 8 x 64KB pages. One page is fixed to F0000-FFFFF, the other seven can be paged in the E0000-EFFFF range. The BIOS is located in the fixed page, DOS and Deskmate are mostly in the paged range.

These 256KB chips can be found in U55 and U57 or U54 and U56, depending on the manufacturer. Tandy used Hitachi chips and Sharp chips, and the two companies' ROM chips had different pinouts. This is why U54 and U55 appear to share the same socket area but they do not. There are two rows of solder holes on each side in each area to accommodate the different pinouts for each chip.

U58 and U59 appear to be the remnant of a design that contemplated using four 128KB chips. U55 and U57 share an EPROM-friendly pinout and the upper address line need not be used, so the motherboard could accomodate a four-chip ROM very easily. However, it is not nor additional ROM expansion.