DM42 specs: doesn't it have 8MB of external flash?

Discussion around the Swiss Micros DM42 calculator.
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invariant
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DM42 specs: doesn't it have 8MB of external flash?

Post by invariant »

Hi,

My understanding is that the DM42 has 1MB of internal flash on the STM32L476Z chip and 8MB of external flash available via QSPI (2MB mapped at 0x90000000 and used as an extension to internal flash and 6MB used to expose a virtual USB FAT disk).

However, https://technical.swissmicros.com/dm42/ ... ifications indicates "32 MBit external flash". Is this a mistake (and it should say "64 MBit" instead), or am I missing something?
toml_12953
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by toml_12953 »

invariant wrote:
Thu Oct 28, 2021 12:12 am
Hi,

My understanding is that the DM42 has 1MB of internal flash on the STM32L476Z chip and 8MB of external flash available via QSPI (2MB mapped at 0x90000000 and used as an extension to internal flash and 6MB used to expose a virtual USB FAT disk).

However, https://technical.swissmicros.com/dm42/ ... ifications indicates "32 MBit external flash". Is this a mistake (and it should say "64 MBit" instead), or am I missing something?
I'm not saying SM did it but some companies buy damaged chips that are functional within a well-defined subset of the original specs. I knew of a computer manufacturer that used 8K dynamic RAM chips. There were no 8K chips manufactured as such but there were defective 16K chips that had only 8K working. The company bought them for a song (cheap!) and sold a home computer with 8K RAM that was very popular. Of course when the yield of 16K RAM chips increased to the point that a full 16K chip was as cheap as a half-good 16K chip, the company bought the 16K chips at the same price it had been paying for 8K and sold 16K upgrades to its users.
Tom L

Some people call me inept but I'm as ept as anybody!
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Peet
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Peet »

Since the DM42 has more than 4MB free memory, 32 Mbit is probably not correct as a memory specification. With SD cards, the memory is usually specified in MB and the speed in Mbit/s - maybe the seconds have been lost.
My programmable calculators - former: CBM PR100, HP41CV, HP28S, HP11C - current: HP48G(256kB), HP35S, Prime, DM41X, DM42
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Over_score
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Over_score »

Here the DM42 memory map:
0x08000000 to 0x0804FFFF 320 KB flash inside ST32L476 reserved for DMCP
0x08050000 to 0x080FFFFF 704 KB flash inside ST32L476 programs like free42, WP34S, WP43S, …
0x10000000 to 0x10007FFF 32 KB high-performance RAM (with hardware parity check) a part of this RAM is used by DMCP
0x20000000 to 0x20017FFF 96 KB RAM
0x90000000 to 0x907FFFFF 8192 KB of external flash

The external flash is split the following way:
0x90000000 to 9x901FFFFF 2036 KB for system and user data
0x901FD000 to 9x901FDFFF 4 KB reserved for DMCP
0x901FE000 to 9x901FFFFF 8 KB for ?
0x90200000 to 0x907FFFFF 6144 KB for the FAT file system
DM42 SN00284 running free42 & SN03835 running WP43S, DM15L, HP41CV, HP42S, HP35s, WP34S, HP Prime
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Walter
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Walter »

Some nitpicky questions:
  • Which part of the 32kB is used by DMCP?
  • How are system and user data separated within the 2036kB?
  • How much of the 2036kB are used by the system?
EDIT: I solemnly withdraw my questions 2 and 3 since the answers depend on the sysem programmed (not the basic system of the calculator as I had assumed).
Question 1 remains, however: How much of the 32kB is used by DMCP?
DM42 SN: 00041 β
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HP-35, HP-45, ..., HP-35S; WP 34S & WP 31S for obvious reasons; DM16L
jwiede
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by jwiede »

Peet wrote:
Thu Oct 28, 2021 8:55 am
Since the DM42 has more than 4MB free memory, 32 Mbit is probably not correct as a memory specification. With SD cards, the memory is usually specified in MB and the speed in Mbit/s - maybe the seconds have been lost.
Yeah, that whole "32Mbit" answer really doesn't make much sense. They really should correct the tech specs to say 8MB (or is it mb for mebibyte?) QSPI Flash, or if they want to get really detailed, 1mb SoC Flash + 8mb QSPI Flash for storage (some used by OS/env).
DM42(ordered), DM16L(sn:4068)
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Walter
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Walter »

jwiede wrote:
Mon Nov 29, 2021 3:35 am
They really should correct the tech specs to say 8MB (or is it mb for mebibyte?) QSPI Flash, or if they want to get really detailed, 1mb SoC Flash + 8mb QSPI Flash for storage (some used by OS/env).
Please remember: bit is small and byte is greater, hence Mb for megabit and MB for megabyte. And if you don't want to signal you believe in millibit or millibyte, abbreviate mega using a capital M, please. (I hardly observe any people on this side of the pond with such unit spelling problems. Don't get me guessing about the causes.)
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Peet
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Peet »

Walter wrote:
Mon Nov 29, 2021 6:04 am
Please remember: bit is small and byte is greater, hence Mb for megabit and MB for megabyte.
SwissMicros use "MBit" :mrgreen:
My programmable calculators - former: CBM PR100, HP41CV, HP28S, HP11C - current: HP48G(256kB), HP35S, Prime, DM41X, DM42
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Walter
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Re: DM42 specs: doesn't it have 8MB of external flash?

Post by Walter »

Peet wrote:
Mon Nov 29, 2021 9:08 am
Walter wrote:
Mon Nov 29, 2021 6:04 am
Please remember: bit is small and byte is greater, hence Mb for megabit and MB for megabyte.
SwissMicros use "MBit" :mrgreen:
Swiss exactitude :roll:
DM42 SN: 00041 β
WP 43S running on this device

HP-35, HP-45, ..., HP-35S; WP 34S & WP 31S for obvious reasons; DM16L
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