Can you use two 2732A EPROMs and replace the two 4KB ROMs in a socketed BASIC rev A brown cartridge?

[ACML]

I looking at using two 300ns 2732A EPROMS to replace the two 4KB Rev A ROM chips with Rev C Burned on the EPROMS.  Any reason why this would not work?

 

[Rybags]

Possibly access time?

I remember a magazine article on Ram upgrades that noted requirement of 250ns or lower - that equates to just under half a machine cycle.

Though ROM is a bit different in that it gets the CS and address rather than Row/Column during fractions of a cycle so maybe it'll be OK.

[cx2k]

39 minutes ago, ACML said:

I looking at using two 300ns 2732A EPROMS to replace the two 4KB Rev A ROM chips with Rev C Burned on the EPROMS.  Any reason why this would not work?

 

I would think you'll need to modify the board to accept eproms which usually have different pin out than masked roms. 

[ACML]

45 minutes ago, cx2k said:

I would think you'll need to modify the board to accept eproms which usually have different pin out than masked roms. 

This is what I was afraid of.  The 24 pin package and 8KB is not as straight forward as the 28 pin package.  I'm asking as by now if it were compatible, I would have read about it by now.  An easy way to upgrade a Rev A to Rev C BASIC.  To date, I've never heard anyone try it.  This might be the reason.

 

Edited June 6, 2023 by ACML

[cx2k]

35 minutes ago, ACML said:

This is what I was afraid of.  The 24 pin package and 8KB is not as straight forward as the 28 pin package.  I'm asking as by now if it were compatible, I would have read about it by now.  An easy way to upgrade a Rev A to Rev C BASIC.  To date, I've never heard anyone try it.  This might be the reason.

 

Best Electronics lists the Rev C Basic cart on their website for $20.

[_The Doctor__]

They used to just sell the roms themselves as well

[cx2k]

57 minutes ago, _The Doctor__ said:

They used to just sell the roms themselves as well

Yes, but the site says currently sold out.

 

[BillC]

5 hours ago, ACML said:

I looking at using two 300ns 2732A EPROMS to replace the two 4KB Rev A ROM chips with Rev C Burned on the EPROMS.  Any reason why this would not work?

The following link has information on replacing both 4KB ROMs with a single 8KB 2764 EPROM:

https://www.insentricity.com/a.cl/200/A800-2764

[+mytek]

An for those that may not be aware, there is a modern CMOS EEPROM that is available to replace the former windowed UV eraseable 2764, which is still in current production and sold by the likes of Digi-Key and Mouser (P/N: AT28C64B-PU15)

 

AT28C64B Pin-out compared to original 2764

So long as pin 27 is tied to +5V it should work.

 

I've used these with great success on a couple of retro computer and console projects, with the benefit of being able to re-flash them without needing a UV light source, and having much lower power requirements due to the CMOS technology. The TL866II Plus programmer supports these newer chips.

[manterola]

Another option is to use this PCBs so you don't need to modify the original one. These PCBs are compatible with the standard brown cartridges.

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